BP201T Human Anatomy and Physiology II โ€” GPAT Question Bank

Year 1 Semester 2 ยท PCI B.Pharm ยท 100 MCQ ยท 5 Units ยท Print-Ready High-Yield Boxes

Authored by Mr. K. Mallikarjuna Reddy, Associate Professor, Vasantidevi Patil Institute of Pharmacy, Kodali ยท KMR Advice

๐Ÿ“– About this Question Bank

100 MCQs across 5 PCI units for BP201T Human Anatomy and Physiology II with a 3-tier honesty label system: GPAT [YEAR] = verified from PYQ master index 2013-2025, Most Probable = classical recurring themes, Practice Question = style-matched practice. Each MCQ has a detailed right-answer explanation + brief wrong-answer explanations. Each unit ends with a print-ready high-yield summary box.

UnitTopicsQuestions
INervous System (advanced) ยท ANS ยท Special Senses ยท Synaptic TransmissionQ1 โ€“ Q20
IIDigestive System (detailed) ยท Energy Metabolism ยท BMR ยท VitaminsQ21 โ€“ Q40
IIIEndocrine System โ€” All Glands + Hormones + DisordersQ41 โ€“ Q60
IVReproductive System ยท Pregnancy ยท Lactation ยท ContraceptionQ61 โ€“ Q80
VRenal/Urinary ยท Body Fluids ยท Immune System ยท Skin (Integument)Q81 โ€“ Q100
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UNIT I
Nervous System Advanced ยท ANS ยท Special Senses ยท Synaptic Transmission (Q1 โ€“ Q20)
1
The CNS includes: GPAT 2014

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: CNS = brain + spinal cord. PNS = 12 pairs cranial nerves + 31 pairs spinal nerves + autonomic NS (sympathetic + parasympathetic + enteric). Brain protected by: (a) cranium; (b) 3 meninges (dura โ†’ arachnoid โ†’ pia); (c) CSF (~ 150 mL produced in choroid plexus, circulated via lateral โ†’ 3rd โ†’ cerebral aqueduct โ†’ 4th ventricle โ†’ foramina of Magendie + Luschka โ†’ subarachnoid space โ†’ arachnoid villi โ†’ sagittal sinus); (d) BBB (tight-junction endothelium + astrocyte end-feet + pericytes; selective permeability โ€” lipophilic + small + transporter-mediated; blocks polar drugs). Brain regions: Cerebrum (4 lobes โ€” frontal motor + Broca speech, parietal sensory + spatial, temporal auditory + Wernicke language + memory hippocampus, occipital vision); Cerebellum (motor coordination, posture, balance โ€” ipsilateral; lesion โ†’ ataxia, dysmetria, intention tremor, dysdiadochokinesia, scanning speech); Brainstem (midbrain โ€” reflexes, dopamine substantia nigra; pons โ€” sleep-wake, respiratory; medulla โ€” cardiovascular + respiratory + emetic centres + vital functions); Diencephalon (thalamus โ€” sensory relay; hypothalamus โ€” homeostasis, ANS, endocrine; epithalamus โ€” pineal melatonin, habenula); Basal ganglia (caudate + putamen + globus pallidus + subthalamic + substantia nigra โ€” motor planning + initiation; lesion โ†’ Parkinson, Huntington, Wilson, hemiballismus); Limbic system (hippocampus memory, amygdala emotion, cingulate, mammillary bodies โ€” Korsakoff). Spinal cord ends at L1-L2 (conus medullaris); cauda equina + filum terminale below; LP at L3-L4/L4-L5.
โœ˜ A wrong: Brain alone misses spinal cord.
โœ˜ B wrong: Spinal cord alone misses brain.
โœ˜ D wrong: Peripheral nerves = PNS.
2
The autonomic nervous system has 2 main divisions: GPAT 2016

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: ANS controls involuntary functions (visceral, glandular, cardiac, smooth muscle). Sympathetic NS (SNS): thoracolumbar T1-L2; pre-ganglionic short ACh on N_N nicotinic ganglion; post-ganglionic long noradrenaline (NE) on ฮฑ + ฮฒ adrenergic receptors (exception: sweat glands cholinergic M3 sympathetic; adrenal medulla = modified ganglion releases adrenaline 80 % + NE 20 % directly to blood). Parasympathetic NS (PSNS): craniosacral โ€” CN III (Edinger-Westphal โ†’ ciliary ganglion โ†’ eye), CN VII (superior salivatory โ†’ submandibular + pterygopalatine ganglia โ†’ lacrimal + submandibular + sublingual glands), CN IX (inferior salivatory โ†’ otic ganglion โ†’ parotid), CN X (dorsal motor nucleus โ†’ thoracoabdominal viscera to splenic flexure โ€” heart, lungs, GI, liver, gallbladder, pancreas, small intestine, proximal colon); + sacral S2-S4 (pelvic splanchnic โ†’ distal 1/3 colon + rectum + bladder + erection). Pre-ganglionic long ACh on N_N; post-ganglionic short ACh on M1-M5 muscarinic. Adrenergic receptors: ฮฑ1 (Gq-PLC-IP3; vasoconstriction skin/splanchnic, pupil mydriasis, GU sphincter, intestinal sphincter); ฮฑ2 (Gi; pre-synaptic โ†“ NE release; vasoconstriction; pancreatic ฮฒ cell โ†“ insulin); ฮฒ1 (Gs; โ†‘ HR/contractility/AV conduction; renin from JG cells; lipolysis); ฮฒ2 (Gs; bronchodilation, vasodilation skeletal+coronary, glycogenolysis, uterine relaxation); ฮฒ3 (Gs; lipolysis adipose, bladder relaxation). Muscarinic: M1 (CNS, gastric acid via ECL); M2 (cardiac โ€” โ†“ HR + AV conduction; pre-synaptic โ†“ ACh release); M3 (smooth muscle contraction, glandular secretion, pupil constriction sphincter pupillae, ciliary muscle contraction near vision); M4-M5 (CNS). Enteric NS ("2nd brain"; Auerbach's myenteric โ€” motility; Meissner's submucosal โ€” secretion + blood flow). Ganglion blockers (trimethaphan, hexamethonium) block both โ€” historical antihypertensive; obsolete.
โœ˜ A wrong: Somatic nervous system division.
โœ˜ C wrong: Vol/invol = somatic vs autonomic.
โœ˜ D wrong: Cranial / spinal = nerve origin.
3
Sympathetic stimulation of ฮฒ1 receptor in cardiac SA node causes: GPAT 2018

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: ฮฒ1 (Gs-coupled) on SA + AV nodes + ventricular myocardium โ†’ adenylyl cyclase โ†’ โ†‘ cAMP โ†’ PKA โ†’ phosphorylates HCN channel (I_f funny current; โ†‘ slope of phase 4 spontaneous depolarisation in pacemaker cells โ†’ โ†‘ HR; "chronotropy") + L-type Caยฒโบ channels (โ†‘ contractility "inotropy"; โ†‘ AV conduction "dromotropy") + phospholamban (โ†“ inhibition of SERCA โ†’ โ†‘ Caยฒโบ reuptake into SR โ†’ faster relaxation "lusitropy"). Net: โ†‘ HR + โ†‘ contractility + โ†‘ AV conduction + faster relaxation = "chronotropy + inotropy + dromotropy + lusitropy" all positive. Vagal (M2 cholinergic) opposite: โ†“ HR + โ†“ AV conduction (negative chrono-/dromotropy). ฮฒ-receptor pharmacology: (a) ฮฒ-agonists โ€” isoprenaline (ฮฒ1+ฮฒ2 non-selective; classical research drug), dobutamine (ฮฒ1 selective; cardiogenic shock + decompensated HF; positive inotropy + mild โ†‘ HR), salbutamol/albuterol (ฮฒ2 selective; asthma SABA; tachycardia + tremor side effect at high dose), salmeterol/formoterol (LABA), terbutaline, ritodrine (uterine relaxant tocolytic โ€” historical), adrenaline/epinephrine (ฮฑ1+ฮฒ1+ฮฒ2; anaphylaxis IM 1:1000 0.3-0.5 mg adult; cardiac arrest IV 1:10000 1 mg). (b) ฮฒ-blockers โ€” non-selective propranolol (HT, angina, arrhythmia, migraine, essential tremor, thyroid storm, anxiety performance, hyperthyroidism adjunct, oesophageal varices); ฮฒ1-selective metoprolol/atenolol/bisoprolol/nebivolol (HF + CAD + HT โ€” preferred over non-selective); ฮฑ+ฮฒ labetalol/carvedilol (HT crisis, HF); non-selective with ISA pindolol/acebutolol. Side effects: bradycardia, AV block, fatigue, โ†“ exercise tolerance, bronchospasm (ฮฒ2 โ€” avoid in asthma/COPD), masking hypoglycaemia symptoms, peripheral coldness, sexual dysfunction, sleep disturbance. Abrupt withdrawal โ†’ rebound tachycardia + HT + angina (taper over 1-2 weeks). SA node: dominant pacemaker in right atrium; intrinsic rate 60-100 bpm; supplied by SA nodal artery (RCA 60 % / LCx 40 %). AV node: 40-60 bpm; delay 0.1 s allows atrial-to-ventricular filling. Bundle of His + Purkinje 30-40 bpm. Hierarchical pacemaker.
โœ˜ B wrong: โ†“ HR = M2 vagal.
โœ˜ C wrong: Definite effect.
โœ˜ D wrong: Bronchodilation = ฮฒ2 (lung).
4
Acetylcholine is the neurotransmitter at: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: ACh used at: (1) all autonomic pre-ganglionic synapses (sympathetic + parasympathetic; ACh โ†’ N_N nicotinic ganglionic receptor โ€” pentameric ligand-gated cation channel); (2) parasympathetic post-ganglionic to effector (ACh โ†’ M1-M5 GPCR); (3) somatic neuromuscular junction (ACh โ†’ N_M muscle nicotinic โ€” different subunit composition: ฮฑ2ฮฒฮตฮด adult, ฮฑ2ฮฒฮณฮด fetal/denervated); (4) sympathetic sweat glands (anomaly โ€” cholinergic sympathetic; ACh โ†’ M3); (5) some sympathetic vasodilator fibres (skeletal muscle blood vessels in some species). ACh pharmacology: (a) Synthesis: choline + acetyl-CoA โ†’ ACh by choline acetyltransferase (ChAT). (b) Storage: VAChT into vesicles. (c) Release: Caยฒโบ-dependent exocytosis (SNARE proteins โ€” syntaxin + SNAP-25 + synaptobrevin; botulinum toxin cleaves SNAP-25 โ†’ blocks release โ†’ flaccid paralysis). (d) Termination: rapid hydrolysis by acetylcholinesterase (AChE; choline + acetate; choline reuptake by CHT1 transporter; acetate metabolised). (e) Cholinergic agonists: directly acting (muscarinic โ€” pilocarpine for glaucoma + Sjรถgren's xerostomia; bethanechol for urinary retention + post-op ileus; methacholine for bronchial provocation testing); nicotinic (nicotine; varenicline partial). (f) Cholinesterase inhibitors (indirectly acting): reversible โ€” physostigmine (crosses BBB; anticholinergic delirium reversal); neostigmine + pyridostigmine (myasthenia gravis; reversal of non-depolarising NMBA); edrophonium (Tensilon test โ€” historical MG diagnosis; very short-acting); donepezil + rivastigmine + galantamine (Alzheimer disease โ€” central AChE inhibition). Irreversible โ€” organophosphates (insecticides + nerve agents โ€” see BP104T Q87). Antidotes: atropine + 2-PAM. (g) Cholinergic antagonists (anticholinergics): muscarinic โ€” atropine (mydriasis, antidote for OP/carbamate, bradycardia, "pre-medication" pre-op), scopolamine (motion sickness TD patch, anaesthesia premedication), homatropine (mydriasis short-acting), tropicamide (mydriatic ophthalmic โ€” short-acting), hyoscyamine, tolterodine + oxybutynin + solifenacin + darifenacin + fesoterodine + trospium (overactive bladder), glycopyrrolate (pre-op antisialagogue + hyperhidrosis), ipratropium + tiotropium (inhaled bronchodilator โ€” COPD/asthma), benztropine + trihexyphenidyl (Parkinson + EPS), dicyclomine (IBS antispasmodic). Nicotinic โ€” N_N: trimethaphan, hexamethonium (ganglion blockers โ€” historical HT). N_M: tubocurarine, atracurium, vecuronium, rocuronium, pancuronium (non-depolarising NMBA; reversed by neostigmine + glycopyrrolate or sugammadex for aminosteroid types); succinylcholine (depolarising NMBA โ€” sustained nicotinic stimulation โ†’ desensitisation).
โœ˜ A wrong: Sympathetic post-ganglionic mostly NE (except sweat).
โœ˜ B wrong: Multiple sites.
โœ˜ D wrong: Sympathetic post-ganglionic mostly NE.
5
Reflex arc components (5): GPAT 2017

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Reflex arc โ€” basic functional unit of nervous system; rapid involuntary stereotyped response to stimulus. 5 components: (1) Receptor โ€” detects stimulus (mechanoreceptor, nociceptor, thermoreceptor, photoreceptor, chemoreceptor); (2) Afferent (sensory) neuron โ€” carries info from receptor to CNS (DRG cell body); (3) Integration centre โ€” spinal cord (most reflexes) or brainstem (cranial reflexes); may be monosynaptic (1 synapse โ€” stretch reflex/myotatic), oligosynaptic, or polysynaptic (multiple โ€” withdrawal); (4) Efferent (motor) neuron โ€” carries response from CNS to effector; (5) Effector โ€” muscle (somatic motor โ†’ skeletal; visceral motor โ†’ smooth/cardiac muscle), gland. Types of reflexes: (1) Stretch (myotatic) reflex โ€” monosynaptic; muscle spindle stretched โ†’ Ia afferent โ†’ ฮฑ-motor neuron โ†’ contraction of same muscle (homonymous) + reciprocal inhibition of antagonist via Ia inhibitory interneuron. Examples: knee jerk (patellar) L3-L4; biceps C5-C6; triceps C7-C8; brachioradialis C5-C6; ankle (Achilles) S1-S2. Tested for upper motor neuron (UMN) lesion (hyperreflexia) vs lower motor neuron (LMN) lesion (hyporeflexia/areflexia). Reflex grading: 0 absent, 1+ โ†“, 2+ normal, 3+ โ†‘, 4+ โ†‘โ†‘ with clonus. (2) Inverse stretch reflex / autogenic inhibition โ€” Golgi tendon organ in tendon detects tension โ†’ Ib afferent โ†’ inhibitory interneuron โ†’ โ†“ ฮฑ-motor neuron firing of same muscle โ†’ muscle relaxes; protects tendon from rupture. Classic clasp-knife rigidity reverse mechanism. (3) Withdrawal (flexor) reflex + crossed extensor โ€” polysynaptic; nociceptive stimulus โ†’ afferent โ†’ multiple interneurons โ†’ ipsilateral flexor activation + ipsilateral extensor inhibition + contralateral extensor activation (crossed extensor โ€” supports body weight while injured side withdraws). (4) Babinski sign / plantar reflex โ€” stroke lateral sole + arch โ†’ big toe up + fanning of others (extensor / Babinski-positive) = abnormal > 2 yr indicating UMN/corticospinal lesion. Normal = downgoing (flexor). Babinski-positive = newborn (myelin immature) โ†’ up to 2 yr OK. (5) Pupillary light reflex โ€” light โ†’ CN II โ†’ pretectal nucleus (Edinger-Westphal nuclei bilaterally) โ†’ CN III โ†’ ciliary ganglion โ†’ sphincter pupillae โ†’ bilateral miosis (direct + consensual). Marcus Gunn pupil = afferent pupillary defect (light in affected eye โ†’ less constriction than light in unaffected). (6) Corneal blink reflex (CN V1 afferent โ†’ CN VII efferent). (7) Gag reflex (CN IX afferent โ†’ CN X efferent). (8) Cough reflex (CN X). (9) Vagal/Vasovagal reflex (CN X). (10) Baroreceptor reflex (carotid sinus/aortic arch โ†’ CN IX/X โ†’ NTS โ†’ BP regulation). (11) Neonatal primitive reflexes: Moro (startle), rooting, suck, palmar grasp, plantar grasp, ATNR (asymmetric tonic neck), step, Galant โ€” disappear by 4-6 mo (CNS maturation); persistence = developmental concern.
โœ˜ A wrong: Missing components.
โœ˜ B wrong: Missing receptor + integrator + effector.
โœ˜ C wrong: Anatomical, not functional.
6
The principal inhibitory neurotransmitter in the CNS is: GPAT 2019

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: GABA (ฮณ-aminobutyric acid) = principal inhibitory NT in brain. Synthesised from glutamate by glutamic acid decarboxylase (GAD; B6/PAL cofactor). Receptors: GABA_A (ionotropic ligand-gated Clโป channel โ€” IPSP via Clโป influx hyperpolarisation; pentamer ฮฑ/ฮฒ/ฮณ subunits; site for benzodiazepines [โ†‘ frequency of channel opening at allosteric site], barbiturates [โ†‘ duration], alcohol, neurosteroids โ€” allopregnanolone โ€” postpartum depression treatment, propofol, etomidate, volatile anaesthetics; flumazenil = BZD antagonist; gabapentin/pregabalin actually act on ฮฑ2ฮด Ca channel not GABA), GABA_B (metabotropic Gi โ€” โ†“ cAMP + opens Kโบ + closes Caยฒโบ; activated by baclofen โ€” spasticity from MS, SCI, CP; intrathecal pump for severe spasticity). Glycine = principal inhibitory NT in spinal cord + brainstem; ionotropic Gly receptor (Clโป channel); strychnine antagonist โ†’ tetanic spasms; also co-agonist (with glutamate) at NMDA receptor. Glutamate = major excitatory NT in CNS; receptors: ionotropic (AMPA, kainate, NMDA โ€” Caยฒโบ permeable, voltage + ligand-gated, glycine co-agonist, requires Mgยฒโบ removal for activation, NMDA hypoactivity โ†’ schizophrenia model; ketamine + memantine + dextromethorphan + phencyclidine = NMDA antagonists) + 8 metabotropic mGluR groups I-III. Excitotoxicity (excessive glutamate โ†’ Caยฒโบ overload โ†’ cell death) โ€” stroke, TBI, ALS, Huntington. Dopamine โ€” 4 pathways: nigrostriatal (motor; Parkinson SN pars compacta loss), mesolimbic (reward/positive psychotic Sx, addiction), mesocortical (cognition/negative Sx schizophrenia), tuberoinfundibular (PRL inhibition; antipsychotic D2 block โ†’ hyperprolactinaemia + galactorrhoea + amenorrhoea). Synthesis: tyrosine โ†’ DOPA (TH rate-limiting, BH4 cofactor) โ†’ DA โ†’ NE (DBH) โ†’ adrenaline (PNMT, in adrenal). Receptors D1-D5 (D1+D5 Gs โ†‘ cAMP; D2-D4 Gi โ†“ cAMP). Serotonin (5-HT) โ€” raphe nuclei โ†’ mood, sleep, appetite, vomiting (CTZ), GI motility. Synthesis: tryptophan โ†’ 5-HTP (Trp hydroxylase rate-limiting) โ†’ 5-HT (AAAD). Receptors 5-HT1-7. SSRIs (fluoxetine, sertraline, escitalopram, paroxetine, citalopram); SNRIs (venlafaxine, duloxetine); MAOIs (phenelzine, tranylcypromine); TCAs (amitriptyline, nortriptyline, imipramine, clomipramine); 5-HT3 antagonists (ondansetron โ€” antiemetic). Serotonin syndrome (multiple serotonergic + MAOi/MB/tramadol) โ€” autonomic instability + tremor + clonus + hyperthermia. Norepinephrine โ€” locus coeruleus โ†’ attention + arousal + stress + fight-or-flight; also peripheral sympathetic. Histamine โ€” tuberomamillary nucleus โ†’ wakefulness (H1 antagonists sedative). Acetylcholine โ€” basal nucleus of Meynert โ†’ memory (Alzheimer cholinergic loss; donepezil/rivastigmine/galantamine AChE inhibitors); also parasympathetic + NMJ. Endogenous opioids โ€” endorphins, enkephalins, dynorphins at ฮผ/ฮด/ฮบ receptors. Neuropeptides โ€” substance P (pain), CCK (anxiety + satiety), VIP, somatostatin, galanin, oxytocin, vasopressin, NPY, ghrelin, leptin.
โœ˜ B wrong: Glutamate = excitatory.
โœ˜ C wrong: Dopamine various effects.
โœ˜ D wrong: ACh mostly excitatory.
7
Synaptic transmission steps (in order): Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Chemical synaptic transmission steps: (1) AP arrival at presynaptic terminal. (2) Voltage-gated Caยฒโบ channels open (P/Q-type at most CNS synapses; N-type also; L-type in cardiac/smooth) โ†’ Caยฒโบ influx. (3) Caยฒโบ-triggered exocytosis: vesicles fuse with presynaptic membrane via SNARE complex (v-SNARE synaptobrevin/VAMP + t-SNAREs syntaxin + SNAP-25; synaptotagmin = Caยฒโบ sensor). (4) NT release into synaptic cleft (~ 20-50 nm wide). (5) NT diffusion + receptor binding on postsynaptic membrane. (6) Receptor activation: ionotropic (ligand-gated ion channel โ€” fast, ms) or metabotropic (GPCR โ†’ second messenger cAMP/IP3/DAG/Caยฒโบ โ€” slower, sec-min). (7) Postsynaptic potential: EPSP (excitatory; depolarising; Na+/Caยฒโบ in or K+ out at GABA_B; e.g., glutamate AMPA/NMDA โ†’ Na+ in) or IPSP (inhibitory; hyperpolarising; Clโป in or K+ out; e.g., GABA_A โ†’ Clโป in). (8) Summation at axon hillock (spatial โ€” multiple inputs simultaneously; temporal โ€” same input rapid succession) โ†’ if threshold reached โ†’ AP propagates. (9) NT termination: (a) reuptake (presynaptic transporter โ€” SERT 5-HT, NET NE, DAT DA, GLT/GLAST glutamate, GAT GABA, GlyT glycine โ€” block = SSRIs, SNRIs, cocaine/methylphenidate inhibit DAT, etc.); (b) enzymatic breakdown (AChE for ACh; MAO + COMT for catecholamines; uncommon for amino acid NTs); (c) diffusion away. (10) Vesicle recycling (clathrin-mediated endocytosis, kiss-and-run, ultrafast endocytosis). Botulinum toxin (Clostridium botulinum) โ€” cleaves SNARE proteins (different toxin types: A, E cleave SNAP-25; B, D, F, G cleave synaptobrevin; C1 cleaves syntaxin) โ†’ blocks ACh release โ†’ flaccid paralysis. Therapeutic uses: blepharospasm, strabismus, hyperhidrosis, cervical dystonia, chronic migraine prophylaxis (PREEMPT 2010), spasticity, achalasia, urinary incontinence (detrusor injection), cosmetic glabellar lines + crow's feet (Botox/Dysport/Xeomin/Jeuveau). Type A (most common โ€” Botox/Dysport/Xeomin); type B (Myobloc โ€” for Botox-A failure). Therapeutic dose tiny vs lethal LD50 ~ 1 ng/kg IV. Tetanus toxin (Clostridium tetani) โ€” same SNARE cleavage as botulinum but at central inhibitory interneurons (Renshaw cells) โ†’ blocks GABA + glycine release โ†’ unopposed motor activity โ†’ spastic paralysis ("lockjaw" trismus, opisthotonus, risus sardonicus). Treatment: human tetanus immunoglobulin + metronidazole/penicillin + supportive (intubation, sedation, NMBA, magnesium); prevent with vaccination (DPT, Td, Tdap; booster q10 yr). Electrical synapses: minority; gap junctions (connexin 43 + others); rapid bidirectional current flow; cardiac (intercalated disc), smooth muscle, neurons (some โ€” eye retina, hippocampus, brainstem, embryonic).
โœ˜ A wrong: AP first then Ca then release.
โœ˜ C wrong: Most are chemical (electrical minority).
โœ˜ D wrong: NT crosses anterograde.
8
Photoreceptors of the retina include: GPAT 2015

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Retinal photoreceptors: rods + cones (modified bipolar neurons with outer segment containing photopigment-rich discs). Rods ~ 120 million; rhodopsin = opsin + 11-cis-retinal (vitamin A derivative); high sensitivity (single photon detectable); scotopic (dim light) + black-white only; concentrated peripheral retina; absent at fovea; slow recovery (rhodopsin regeneration takes minutes). Cones ~ 6 million; 3 types of opsin: S-cones (short wavelength ~ 420 nm blue), M-cones (~ 530 nm green), L-cones (~ 560 nm red); high spatial acuity (fovea โ€” 1:1 cone:ganglion ratio for fine vision); photopic (bright light) + colour vision; less sensitive than rods. Phototransduction (rod): 11-cis-retinal + light โ†’ all-trans-retinal โ†’ conformation change โ†’ rhodopsin activated โ†’ activates transducin (Gt G-protein ฮฑ subunit GTP exchange) โ†’ activates phosphodiesterase (PDE) โ†’ hydrolyses cGMP โ†’ โ†“ cytosolic cGMP โ†’ cGMP-gated cation channels (CNG) close โ†’ โ†“ Naโบ/Caยฒโบ influx โ†’ photoreceptor hyperpolarises (from โˆ’40 to โˆ’70 mV โ€” opposite of most neurons; in dark photoreceptors are depolarised + tonically release glutamate). Hyperpolarisation โ†’ โ†“ glutamate release at bipolar synapse โ†’ bipolar cells either excited (ON-bipolar) or inhibited (OFF-bipolar) โ†’ ganglion cells AP โ†’ optic nerve โ†’ LGN โ†’ V1 visual cortex. Visual pathway: retina โ†’ optic nerve (CN II) โ†’ optic chiasm (nasal fibres cross โ€” temporal field projects to contralateral hemisphere) โ†’ optic tract โ†’ LGN of thalamus โ†’ optic radiations (Meyer's loop superior โ€” temporal lobe โ€” carries inferior visual field; parietal โ€” superior visual field) โ†’ primary visual cortex V1 (Brodmann 17, calcarine sulcus). Retina layers (10 layers; light passes inverted through to back where photoreceptors located): RPE (retinal pigment epithelium โ€” phagocytose discs, blood-retinal barrier, recycle retinal) โ†’ photoreceptor (outer segment with discs) โ†’ outer limiting membrane โ†’ outer nuclear (rod/cone nuclei) โ†’ outer plexiform (synapse photoreceptor-bipolar; horizontal cells lateral inhibition) โ†’ inner nuclear (bipolar + horizontal + amacrine + Mรผller) โ†’ inner plexiform (bipolar-ganglion synapse; amacrine modulation) โ†’ ganglion cell (axons โ†’ optic nerve) โ†’ optic nerve fibre layer โ†’ inner limiting membrane. Optic disc = ganglion cell axons exit; no photoreceptors โ†’ blind spot. Macula โ†’ fovea (1.5 mm; cone-only; highest acuity; foveola centre 0.35 mm). Ophthalmic disorders: myopia (corrected concave lens), hyperopia (convex), astigmatism (cylindrical), presbyopia (reading glasses post-40 yr โ€” lens elasticity loss), cataract (lens opacity), glaucoma (โ†‘ IOP โ†’ optic nerve damage), AMD (age-related macular degeneration โ€” dry: drusen + atrophy; wet: choroidal neovascularisation โ€” anti-VEGF intravitreal: bevacizumab/ranibizumab/aflibercept/brolucizumab), diabetic retinopathy (microvascular โ€” non-proliferative + proliferative; treat: glycaemic control + laser + anti-VEGF + vitrectomy), retinal detachment (rhegmatogenous, tractional, exudative; emergent surgery), retinitis pigmentosa (rod loss; night blindness + tunnel vision; genetic), CMV retinitis (HIV/AIDS opportunistic), uveitis (anterior/intermediate/posterior; HLA-B27, sarcoidosis, Behรงet).
โœ˜ B wrong: Bipolar = secondary neurons.
โœ˜ C wrong: Ganglion = output.
โœ˜ D wrong: Mรผller = retinal glia.
9
Ear ossicles in order from tympanic membrane to oval window: GPAT 2017

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: "MIS" Malleus โ†’ Incus โ†’ Stapes ("Many Indians Sleep"). Ear anatomy + physiology: External ear โ€” pinna (auricle; collects sound) + external auditory meatus (outer 1/3 cartilage with ceruminous glands; inner 2/3 bony) + tympanic membrane (TM, eardrum; vibrates with sound). Middle ear โ€” air-filled cavity; ossicles (malleus articulates with TM, incus middle, stapes footplate articulates with oval window of cochlea); 2 muscles โ€” tensor tympani (CN V3 mandibular branch โ€” pulls malleus inward, dampens loud sounds) + stapedius (CN VII facial โ€” pulls stapes, smallest skeletal muscle ~ 1 mm; stapedius reflex โ€” bilateral protective contraction at > 70-90 dB; absent in Bell palsy โ†’ hyperacusis); Eustachian (auditory) tube to nasopharynx (pressure equalisation; Valsalva manoeuvre; otitis media in children โ€” short + horizontal Eustachian tube + supine feeding); mastoid air cells communicate (mastoiditis after OM). Inner ear โ€” bony labyrinth + membranous labyrinth in petrous temporal bone. (a) Cochlea โ€” 2.5 turns spiral; 3 chambers โ€” scala vestibuli (perilymph; Naโบ-rich) + scala media (endolymph; Kโบ-rich; contains organ of Corti) + scala tympani (perilymph). Helicotrema connects vestibuli + tympani at apex. Reissner's membrane separates vestibuli + media; basilar membrane separates media + tympani. Organ of Corti on basilar membrane: 1 row inner hair cells (3500; primary mechanotransducers โ€” 95 % of CN VIII afferent) + 3 rows outer hair cells (12 000; cochlear amplifier โ€” prestin motor protein). Stereocilia connect to tectorial membrane; deflection opens MET (mechanoelectrical transducer) channels โ†’ Kโบ + Caยฒโบ influx โ†’ depolarisation โ†’ glutamate release โ†’ CN VIII afferent. (b) Vestibule โ€” saccule + utricle with maculae (linear acceleration + gravity; otoliths โ€” calcium carbonate crystals on otolithic membrane covering hair cells). (c) 3 semicircular canals (anterior, posterior, horizontal/lateral) โ€” angular acceleration; ampulla at base contains crista ampullaris with cupula on hair cells. Sound transmission: TM vibration โ†’ ossicles โ†’ oval window โ†’ perilymph fluid wave โ†’ basilar membrane displacement โ†’ hair cell deflection โ†’ AP via CN VIII โ†’ cochlear nuclei (medulla) โ†’ superior olive (binaural localisation) โ†’ lateral lemniscus โ†’ inferior colliculus (midbrain โ€” startle reflex) โ†’ MGN (medial geniculate nucleus, thalamus) โ†’ primary auditory cortex (Heschl gyrus, superior temporal gyrus, BA 41-42). Place theory (Bรฉkรฉsy): high frequencies (~ 20 kHz) at base near oval window; low (~ 20 Hz) at apex near helicotrema. Tonotopic organisation maintained throughout pathway. Impedance matching: ossicles overcome air-fluid impedance mismatch (would lose 99.9 % energy); 17ร— lever ratio + 20ร— area ratio (TM 55 mmยฒ to oval window 3.2 mmยฒ) = ~ 22ร— pressure amplification. Hearing tests: Rinne (tuning fork โ€” air conduction AC vs bone conduction BC; normal AC > BC; conductive loss BC > AC; sensorineural AC > BC but both reduced); Weber (tuning fork forehead โ€” lateralises to affected ear in conductive loss, away from affected in SNHL); pure-tone audiometry (250-8000 Hz; threshold dB HL); tympanometry (TM compliance; type A normal, B flat โ€” effusion/perforation, C negative pressure โ€” Eustachian dysfunction); OAE otoacoustic emissions (newborn screening; outer hair cell function); ABR/BAER (objective; assess auditory pathway; for newborns + non-cooperative). Hearing loss types: (a) Conductive (external + middle ear pathology) โ€” cerumen impaction, otitis externa/media, TM perforation, ossicular discontinuity, otosclerosis (stapes fixation; SNHL +CHL), tumour. Treat: remove cerumen, antibiotic for OM, ventilation tubes, stapedectomy. (b) Sensorineural (SNHL) โ€” inner ear/CN VIII/central โ€” presbycusis (age-related; high-frequency first), noise-induced (chronic exposure > 85 dB; hair cell damage), drug-induced (aminoglycosides โ€” gentamicin/streptomycin/amikacin/tobramycin/neomycin; loop diuretics โ€” furosemide; cisplatin โ€” most ototoxic chemotherapy; salicylate; quinine), Mรฉniรจre disease (endolymphatic hydrops โ€” vertigo + tinnitus + SNHL low-frequency + ear fullness; tx: diet low Na, diuretic, intratympanic gentamicin/steroids), labyrinthitis, vestibular schwannoma (CN VIII tumour โ€” SNHL + tinnitus + balance), congenital (TORCH, genetic โ€” Usher, Pendred, connexin 26 GJB2). Treat: hearing aid, cochlear implant (severe-profound bilateral SNHL).
โœ˜ A wrong: Reverse order.
โœ˜ B wrong: Wrong order.
โœ˜ D wrong: Wrong order.
10
Five primary tastes are: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: 5 basic tastes (recognised since umami added 2002): (1) Sweet โ€” T1R2/T1R3 GPCR; sugars (glucose, fructose, sucrose, lactose, maltose), artificial sweeteners (saccharin, aspartame, sucralose, acesulfame-K, stevioside), some amino acids (Gly, Ala, Ser, Thr โ€” sweet), proteins (miraculin, monellin, thaumatin). (2) Sour โ€” Hโบ ions (acids); PKD2L1/OTOP1 channel + acid-sensing channels in taste receptor cells. Citric, acetic, hydrochloric. (3) Salty โ€” Naโบ via ENaC (epithelial sodium channel; same family as kidney; amiloride blocks โ†’ โ†“ salt taste); also Kโบ, Liโบ. (4) Bitter โ€” T2R family (~ 25 GPCRs in humans); detects toxins, alkaloids (quinine, caffeine, nicotine), urea, KCl. Evolutionary defence โ€” many natural toxins are bitter. (5) Umami โ€” T1R1/T1R3; glutamate (MSG monosodium glutamate; identified 1908 Kikunae Ikeda Tokyo from kombu seaweed dashi); aspartate; ribonucleotides IMP (inosine monophosphate; meat, fish) + GMP (guanosine monophosphate; mushrooms โ€” synergistic with glutamate ~ 10-30ร— amplification โ€” "umami bomb" cooking). 5th basic taste recognised. Taste receptor cells grouped in taste buds (~ 5 000-10 000 in humans; lifespan 10-14 days; regenerate from basal cells). Located on papillae: (a) Fungiform (mushroom-shaped; anterior 2/3 tongue; ~ 200; mostly sweet/salty); (b) Circumvallate (vallate) (V-shaped row of 7-12 at terminal sulcus posterior; largest; mostly bitter); (c) Foliate (lateral posterior; sour); (d) Filiform โ€” most numerous but NO taste buds (only tactile + thermal). Taste pathway: anterior 2/3 tongue โ†’ chorda tympani branch of CN VII (facial); posterior 1/3 โ†’ CN IX (glossopharyngeal); epiglottis + larynx โ†’ CN X (vagus). All converge on nucleus tractus solitarius (NTS) in medulla โ†’ VPM (ventral posterior medial) thalamus โ†’ primary gustatory cortex (insula + frontal operculum, Brodmann 43). Taste modulators: gymnemic acid (Gymnema sylvestre โ€” blocks sweet receptors temporarily; Ayurvedic for diabetes); miraculin (miracle berry Synsepalum dulcificum โ€” modifies sour taste to sweet); cynarin (artichoke โ€” sweet water aftertaste). Tongue map myth: classical "tongue map" with discrete taste regions is INCORRECT โ€” all tastes detected throughout tongue (1901 Hรคnig misinterpreted). Other oral sensations (NOT taste โ€” chemesthesis via trigeminal): (a) Spicy / hot (capsaicin from chillies) โ†’ TRPV1 channel (also activated by 43+ ยฐC heat; common pathway โ†’ "burning" feeling); paradoxically used for analgesia โ€” capsaicin cream depletes substance P (8 % patch Qutenza for post-herpetic neuralgia + diabetic neuropathy; also nasal spray). (b) Cool / mint (menthol from peppermint) โ†’ TRPM8 channel (also < 22 ยฐC cold). (c) Astringency (tannins in tea/wine/unripe fruit) โ€” protein precipitation tactile sensation. (d) Numbness / tingle (Sichuan pepper hydroxy-ฮฑ-sanshool; carbonation). (e) Pungent (mustard, wasabi, horseradish โ€” allyl isothiocyanate AITC) โ†’ TRPA1 channel. Flavour = taste (5 basic) + smell (retronasal olfaction; main contributor to flavour; ~ 80 % of "flavour") + texture + temperature + chemesthesis (trigeminal). Disorders: ageusia (no taste; total โ€” rare); hypogeusia (โ†“ taste); dysgeusia (altered/distorted taste). Causes: zinc deficiency (taste blunting, classical), drugs (metformin, ACE-I, antibiotics โ€” metronidazole metallic taste, terbinafine, clarithromycin, captopril), radiation (head/neck cancer therapy), B12 + iron + folate def, smoking, ageing, head trauma, infections (COVID-19 โ€” anosmia + ageusia), Bell palsy, diabetes, hypothyroidism. Treatment: address cause + zinc supplementation + supportive.
โœ˜ A wrong: Misses umami (5th).
โœ˜ C wrong: Chemesthesis not taste.
โœ˜ D wrong: Trigeminal sensations.
11
Olfactory pathway: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: CN I (Olfactory) โ€” only sensory cranial nerve to bypass thalamus + project directly to cortex (limbic + medial temporal). Olfactory receptor neurons (in olfactory epithelium of upper nasal cavity) โ†’ axons through cribriform plate of ethmoid โ†’ olfactory bulb โ†’ mitral + tufted cells โ†’ olfactory tract โ†’ piriform cortex + entorhinal cortex + amygdala (hippocampal, emotional, memory connections โ€” explains powerful smell-memory association โ€” Proust effect). 350 functional olfactory receptor genes (largest gene family humans). Trauma (cribriform plate fracture) + viral infection (COVID-19 transient anosmia) + neurodegeneration (Parkinson + Alzheimer early sign โ€” anosmia as preclinical biomarker) common. Anosmia vs hyposmia + dysosmia (parosmia, phantosmia). Treatment: olfactory training (regular sniffing of strong odorants โ€” rose, eucalyptus, lemon, clove ร— weeks-months; some recovery in post-viral). Smell + flavour: 80 % of "flavour" perception comes from retronasal olfaction (during chewing โ€” odorants travel up nasopharynx); orthonasal = sniffing. Common cold โ†’ temporary loss of taste perceived = mostly olfactory.
โœ˜ B wrong: Cochlea = hearing.
โœ˜ C wrong: Retina = vision.
โœ˜ D wrong: Tongue = taste partially CN VII.
12
Mechanoreceptors in skin include: GPAT 2018

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Skin sensory receptors: (1) Meissner corpuscle (encapsulated; papillary dermis; light touch low-freq flutter 5-50 Hz; rapidly adapting; fingertips, lips, palms โ€” high density). (2) Pacinian corpuscle (onion-like, deep dermis + hypodermis; deep pressure + high-freq vibration 200-300 Hz; rapidly adapting; very sensitive โ€” single Pacinian can detect 1 ฮผm displacement). (3) Ruffini ending (capsulated; deep dermis; sustained stretch + warm temp; slow adapting). (4) Merkel disc (epidermis; sustained light touch + texture + edges; slowly adapting). (5) Hair follicle receptors (around hair shaft; movement of hair). (6) Free nerve endings (pain โ€” Aฮด sharp + C slow burning; itch; temperature โ€” TRPV1 heat/capsaicin, TRPM8 cold/menthol, TRPA1 noxious cold + mustard/wasabi). (7) Krause end-bulbs (cold). (8) Golgi-Mazzoni (vibration). Adaptation: rapidly-adapting (RA โ€” Meissner + Pacinian + hair follicle โ€” onset/offset only; "phasic"); slowly-adapting (SA โ€” Merkel + Ruffini โ€” sustained response; "tonic"). RA detect change; SA encode magnitude. Sensory pathways: (a) Dorsal column-medial lemniscus (DCML) โ€” fine touch + vibration + proprioception + 2-point discrimination; first-order neuron in DRG โ†’ ascends ipsilateral in dorsal column (fasciculus gracilis lower body T6+; cuneatus upper) โ†’ decussates in lower medulla โ†’ medial lemniscus โ†’ VPL thalamus โ†’ S1 primary somatosensory cortex (postcentral gyrus). (b) Spinothalamic / anterolateral โ€” pain + temperature + crude touch; DRG โ†’ enters cord โ†’ 2nd-order neuron in dorsal horn โ†’ decussates IMMEDIATELY through anterior white commissure โ†’ ascends contralateral spinothalamic tract โ†’ VPL โ†’ S1. Clinical sensory loss: (a) Brown-Sรฉquard syndrome (cord hemisection) โ€” ipsilateral DCML + corticospinal loss (paralysis + loss of vibration/proprioception below) + contralateral pain/temperature loss (because spinothalamic decussates at cord level). (b) Tabes dorsalis (syphilis) โ€” DCML loss โ†’ ataxia + Romberg + loss of vibration/proprioception/2-point. (c) Subacute combined degeneration (B12 def) โ€” DCML + lateral corticospinal + peripheral nerve loss. (d) Syringomyelia โ€” central cord cavity โ†’ bilateral pain/temp loss in shoulders + arms (cape distribution; affects decussating spinothalamic fibres in central commissure) but DCML preserved. (e) Polyneuropathy (diabetic) โ€” distal symmetric stocking-glove pattern; small fibre (pain/temp/autonomic) early; large fibre (vibration/proprioception) later. (f) Cortical sensory loss (parietal lesion) โ€” astereognosis (can't identify object by touch), agraphesthesia, neglect, loss of 2-point discrimination. Pain pathophysiology: nociceptive (somatic sharp; visceral diffuse + referred) + neuropathic (burning + tingling + electric โ€” diabetic, post-herpetic, sciatica) + nociplastic (central sensitisation โ€” fibromyalgia). Modulation: gate theory (Aฮฒ touch closes gate to C/Aฮด pain โ€” TENS, rubbing); descending pathways (PAG midbrain โ†’ raphe โ†’ dorsal horn โ€” opioid, serotonergic, noradrenergic).
โœ˜ A wrong: Photoreceptors = retina.
โœ˜ C wrong: Cones = retina.
โœ˜ D wrong: Hair cells = ear.
13
Vestibular system function: GPAT 2020

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Vestibular apparatus (inner ear, bony labyrinth + membranous labyrinth in petrous temporal bone): (1) Utricle + saccule (otolith organs) โ€” linear acceleration + head position relative to gravity; maculae contain hair cells + otoliths (CaCOโ‚ƒ crystals on otolithic membrane); displacement of otoliths under gravity / linear acceleration deflects stereocilia โ†’ MET channel opens โ†’ depolarisation. Utricle (horizontal plane โ€” fore-aft + left-right linear); saccule (vertical โ€” up-down). (2) 3 Semicircular canals (anterior, posterior, horizontal/lateral; orthogonal planes) โ€” angular acceleration / rotational head movement. Each canal has ampulla at base with crista ampullaris (sensory ridge with hair cells covered by gelatinous cupula). Endolymph in canal moves opposite to head rotation (inertia) โ†’ cupula deflects โ†’ hair cells signal. Vestibular pathway: hair cells โ†’ CN VIII vestibular branch โ†’ vestibular nuclei (medulla) โ†’ cerebellum (flocculonodular lobe โ€” vestibulocerebellum), spinal cord (vestibulospinal tract โ€” postural muscle tone), oculomotor nuclei (vestibulo-ocular reflex VOR), thalamus โ†’ cortex (parietal-insular vestibular cortex; spatial awareness). Vestibulo-ocular reflex (VOR): head rotation triggers compensatory eye movement opposite direction โ†’ visual stabilisation during movement. Tested clinically (head impulse test, doll's eyes oculocephalic reflex โ€” present in brainstem function intact). Absent VOR โ†’ oscillopsia (jiggling vision when moving). Vestibular disorders: (1) Benign Paroxysmal Positional Vertigo (BPPV) โ€” most common cause of vertigo; otoliths displaced into semicircular canals (most often posterior canal); transient (< 1 min) positional vertigo with characteristic Dix-Hallpike test โ†’ up-beating + torsional nystagmus. Treatment: Epley manoeuvre (canalith repositioning) โ€” high success rate, > 80 %. (2) Mรฉniรจre disease โ€” endolymphatic hydrops; episodic vertigo (hours) + low-frequency SNHL + tinnitus + ear fullness. Treatment: low-Na diet (~ 1500 mg/day) + diuretic (HCTZ) + intratympanic gentamicin/dexamethasone + vestibular rehabilitation; surgical (endolymphatic sac decompression, labyrinthectomy, vestibular nerve section). (3) Vestibular neuritis / labyrinthitis โ€” viral; acute prolonged vertigo + vomiting, days; supportive (vestibular suppressant short-course โ€” meclizine, prochlorperazine, ondansetron + early vestibular rehabilitation). (4) Vestibular schwannoma (acoustic neuroma) โ€” CN VIII tumour; gradual unilateral SNHL + tinnitus + balance; bilateral = NF2 (neurofibromatosis 2). Tx: observation + surgery + stereotactic radiosurgery (Gamma Knife). (5) Vestibular migraine โ€” episodic vertigo with migraine; same prophylaxis. (6) Motion sickness โ€” visual-vestibular mismatch; pre-treat with scopolamine TD patch + dimenhydrinate / meclizine + ginger. (7) Cerebellar / brainstem stroke โ€” vertigo + cranial nerve signs + ataxia; HINTS exam (Head Impulse + Nystagmus + Test of Skew) โ€” peripheral vs central differentiation. (8) Persistent Postural Perceptual Dizziness (PPPD). (9) Mal de dรฉbarquement. Nystagmus: rhythmic involuntary eye movement; physiological (post-spin) vs pathological. Direction by fast phase. Peripheral (vestibular) nystagmus typically horizontal or torsional; suppressed by visual fixation; more severe symptoms. Central (brainstem/cerebellum) nystagmus may be vertical/pure torsional; not suppressed by fixation; less symptomatic for severity of nystagmus; concerning. Vestibular suppressants (short-term symptom relief โ€” < 72 h to allow central compensation): antihistamines (meclizine, dimenhydrinate, promethazine โ€” also anticholinergic), benzodiazepines (diazepam, lorazepam โ€” short course only), antiemetics (ondansetron, prochlorperazine), scopolamine TD. Avoid prolonged use โ€” delays central compensation.
โœ˜ A wrong: Hearing = cochlea.
โœ˜ B wrong: Vision = retina.
โœ˜ D wrong: Smell = olfactory.
14
Cerebellar function (motor) โ€” primary lesion sign: GPAT 2019

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Cerebellum coordinates voluntary movement (smoothness + accuracy + timing), balance, posture, motor learning. Lesions cause IPSILATERAL signs (input crosses + output crosses โ†’ net ipsilateral). Three lobes: anterior + posterior + flocculonodular. Three peduncles: superior (efferent to red nucleus + thalamus + motor cortex), middle (afferent from pons + cortex), inferior (afferent from spinal cord + vestibular + olive). Cortex: 3 layers โ€” molecular + Purkinje + granular. Purkinje cells = only output to deep cerebellar nuclei (DCN: dentate, emboliform, globose, fastigial โ€” DEGF lateral to medial). Climbing fibres (from inferior olivary nucleus) + mossy fibres (everywhere else) = main inputs. Cerebellar lesion signs ("DANISH" / "Cerebellar GAIT TIPS"): Dysmetria (past-pointing on finger-nose; over/undershoot), Ataxia (gait + trunk + limb โ€” wide-based gait, falls, postural instability), Nystagmus (esp. flocculonodular), Intention tremor (worsens with action approaching target โ€” opposite of Parkinson resting tremor), Scanning dysarthria / scanning speech (slow, syllable separated), Hypotonia ("rag doll"; reduced muscle tone), Dysdiadochokinesia (impaired rapid alternating movement โ€” pronation/supination), Dyssynergia (decomposition of complex movements), Rebound phenomenon, "Drunken" appearance (resembles alcohol intoxication โ€” alcohol primarily depresses cerebellum). Cerebellar syndromes: (a) Cerebellar hemisphere lesion โ€” ipsilateral limb ataxia + dysmetria + intention tremor (e.g., stroke PICA/AICA/SCA territory; tumour). (b) Vermis (midline) โ€” truncal ataxia + gait ataxia + nystagmus (alcoholism preferentially affects anterior vermis โ†’ wide-based gait + lower limb ataxia preserved arm function). (c) Flocculonodular โ€” vestibular signs + nystagmus + balance. (d) Cerebellar cognitive affective syndrome (CCAS / Schmahmann) โ€” non-motor cerebellar function impaired in posterior cerebellum lesion. Cerebellar tests: finger-to-nose (dysmetria + intention tremor); heel-to-shin (lower limb ataxia); rapid alternating (dysdiadochokinesia); tandem walk (gait ataxia); Romberg (proprioceptive โ€” but cerebellar gait worse with eyes open vs sensory ataxia worse with eyes closed). Causes of cerebellar disease: (1) Acute: stroke (PICA, AICA, SCA โ€” Wallenberg lateral medullary, lateral pontine, etc.), tumour (glioma, medulloblastoma โ€” children, cerebellopontine angle tumour vestibular schwannoma), MS, post-infectious (varicella + rubella), trauma. (2) Chronic: alcoholic cerebellar degeneration, paraneoplastic (SCC lung, ovarian โ€” anti-Yo, anti-Hu, anti-Tr antibodies), Friedreich ataxia (autosomal recessive GAA repeat in FXN gene; cardiomyopathy + diabetes + scoliosis + areflexia), spinocerebellar ataxias (SCA 1-40+ ; CAG/CTG repeats), ataxia-telangiectasia (autosomal recessive ATM mutation; childhood progressive ataxia + telangiectasia + immunodeficiency + cancer susceptibility), Wilson disease (Cu deposit; basal ganglia + cerebellum + KF rings), B12 deficiency, hypothyroidism, drugs (phenytoin chronic, lithium toxicity, anticonvulsants). Treatment: address cause (e.g., stop alcohol, replenish B12); rehabilitation; symptomatic (clonazepam for tremor; ฮฒ-blocker; vestibular therapy).
โœ˜ A wrong: Spastic paralysis = corticospinal/UMN.
โœ˜ B wrong: Sensory loss = somatosensory cortex/pathways.
โœ˜ C wrong: Aphasia = dominant temporal/frontal.
15
Basal ganglia disorders include: GPAT 2021

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Basal ganglia (BG) = subcortical nuclei modulating movement initiation + planning + execution + suppressing unwanted movement. Components: caudate + putamen (= striatum; main input) + globus pallidus (internal GPi + external GPe; output via thalamus to cortex) + subthalamic nucleus + substantia nigra (pars compacta SNc with dopaminergic neurons + pars reticulata SNr). Direct + indirect + hyperdirect pathways. Direct pathway (facilitates movement): cortex โ†’ striatum (D1) โ†’ GPi/SNr โ†’ โ†“ thalamus inhibition โ†’ โ†‘ cortex motor โ†’ MOVEMENT. Indirect pathway (inhibits movement): cortex โ†’ striatum (D2) โ†’ GPe โ†’ STN โ†’ GPi/SNr โ†’ โ†‘ thalamus inhibition โ†’ โ†“ cortex โ†’ no movement. Dopamine from SNc balances: D1 stimulates direct (PRO movement); D2 inhibits indirect (PRO movement). Loss of dopamine โ†’ โ†‘ indirect + โ†“ direct โ†’ โ†“ movement (Parkinson hypokinesia). BG disorders: (1) Parkinson disease (PD) โ€” progressive degeneration of SNc dopaminergic neurons โ†’ โ†“ DA in striatum. Lewy bodies (ฮฑ-synuclein aggregates) pathology. Cardinal features (TRAP): Tremor at rest (4-6 Hz, "pill-rolling," distal hand, asymmetric, improves with movement โ€” opposite of cerebellar intention tremor); Rigidity (cogwheel โ€” ratchety; lead-pipe โ€” sustained); Akinesia/bradykinesia (slow movement, hypomimia/masked face, hypophonia, micrographia, shuffling gait + โ†“ arm swing, freezing); Postural instability (late; falls). Other: olfactory loss (early), constipation, REM sleep behavior disorder, depression, dementia (later โ€” Lewy body). Treatment: (a) Levodopa + carbidopa (Sinemet) โ€” gold standard; carbidopa = peripheral DOPA decarboxylase inhibitor (doesn't cross BBB; โ†“ peripheral N/V from peripheral DA + โ†‘ central availability). On-off + dyskinesia after years (dopamine dysregulation; "wearing off"). (b) Dopamine agonists: pramipexole, ropinirole, rotigotine (TD patch), bromocriptine + cabergoline (older, ergot โ€” pulmonary/cardiac fibrosis), apomorphine (rescue SC + sublingual film). Side: nausea, hallucinations, impulse control disorders (gambling, hypersexuality), sleep attacks. (c) MAO-B inhibitors: selegiline, rasagiline, safinamide โ€” slows DA breakdown. (d) COMT inhibitors: entacapone (peripheral; with levodopa), tolcapone (central; hepatotoxicity black-box), opicapone. (e) Anticholinergics: trihexyphenidyl, benztropine โ€” for tremor predominant; avoid elderly (delirium). (f) Amantadine โ€” NMDA antagonist + mild DA effects; for dyskinesia. (g) Deep brain stimulation (DBS) โ€” STN or GPi; for advanced PD with motor fluctuations + dyskinesia. (h) Focused ultrasound thalamotomy โ€” newer non-invasive. (2) Huntington disease โ€” autosomal dominant CAG trinucleotide repeat expansion in HTT gene (chromosome 4); > 35-39 repeats pathologic; anticipation (paternal). Loss of GABAergic medium spiny neurons in caudate (> putamen). Onset 30-50 yr (juvenile rare). Triad: chorea (involuntary jerky dance-like movements) + dementia + behavioural/psychiatric (depression, irritability, suicide common). Caudate atrophy on imaging โ€” "boxcar ventricles" (enlarged frontal horns). Treatment: tetrabenazine + deutetrabenazine + valbenazine (VMAT2 inhibitors โ€” โ†“ DA โ†’ โ†“ chorea); SSRI for depression; antipsychotic for psychosis. Predictive testing controversial. No cure. (3) Wilson disease โ€” autosomal recessive ATP7B mutation; Cu accumulation in liver + brain (basal ganglia โ€” putamen, globus pallidus) + cornea (Kayser-Fleischer rings). Movement disorder: dystonia, parkinsonism, tremor (wing-beating), dysarthria, behavioural; + hepatic; + hemolytic anaemia. Tx: penicillamine + trientine + zinc acetate maintenance. (4) Hemiballismus โ€” large amplitude flinging movements one limb; subthalamic nucleus contralateral lesion (small lacunar stroke); usually self-limited or improves with antipsychotic/tetrabenazine. (5) Tourette syndrome โ€” multiple motor + โ‰ฅ 1 vocal tic; childhood onset; comorbid OCD, ADHD; dopamine dysregulation in BG. Tx: behavioural therapy + ฮฑ2 agonist (clonidine, guanfacine) + antipsychotic (risperidone, aripiprazole, haloperidol โ€” older, EPS) + DBS (severe). (6) Tardive dyskinesia (TD) โ€” chronic DA receptor blockade (typical antipsychotics; older 1st-gen โ€” haloperidol, chlorpromazine; long-term metoclopramide); upregulation D2 supersensitivity; involuntary orofacial + truncal + limb movements; may persist after stopping drug. Tx: VMAT2 inhibitors. (7) Acute dystonia (antipsychotic โ€” torticollis, oculogyric, laryngeal): IV diphenhydramine or benztropine. (8) Akathisia (motor restlessness, antipsychotic side effect). (9) Drug-induced parkinsonism (antipsychotic, metoclopramide).
โœ˜ B wrong: Cerebellar separate.
โœ˜ C wrong: Aphasia = cortex (Broca, Wernicke).
โœ˜ D wrong: Memory = hippocampus.
16
Hypothalamus functions: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Hypothalamus = supreme homeostatic regulator + neuroendocrine link; ~ 4 g; below thalamus, forms floor + lower walls of 3rd ventricle. Mnemonic "HEAL TAN": Hormones, Eating + Autonomic, Libido, Thermoregulation, Adrenergic-stress, Neurosecretion. Key nuclei: (1) Supraoptic + Paraventricular (PVN) โ€” produce ADH (vasopressin) + oxytocin โ†’ axonal transport down infundibulum โ†’ stored + released from posterior pituitary (neurohypophysis). ADH (V2 receptor renal collecting duct โ†’ aquaporin-2 insertion โ†’ water reabsorption; V1 vasoconstriction). Oxytocin (uterine contraction labour; milk letdown reflex via myoepithelial cells). PVN also makes CRH, TRH. (2) Arcuate nucleus โ€” GHRH, GnRH, dopamine (= PIF โ€” prolactin inhibitory factor); NPY/AgRP (orexigenic โ€” โ†‘ appetite) + POMC (anorexigenic โ€” โ†“ appetite, โ†‘ via leptin). (3) Anterior / Preoptic โ€” heat dissipation (vasodilation + sweating); damage โ†’ hyperthermia. Sexually dimorphic nucleus. (4) Posterior โ€” heat conservation (vasoconstriction + shivering); damage โ†’ poikilothermy (body T = ambient). (5) Lateral hypothalamic area โ€” hunger / "feeding centre"; orexin (hypocretin); lesion โ†’ anorexia + wasting; orexin loss โ†’ narcolepsy with cataplexy. (6) Ventromedial nucleus (VMN) โ€” satiety / "satiety centre"; lesion โ†’ hyperphagia + obesity + savage behaviour. (7) Suprachiasmatic nucleus (SCN) โ€” master circadian pacemaker; entrained by light via retinohypothalamic tract (melanopsin-containing intrinsically photosensitive retinal ganglion cells); regulates pineal melatonin (released in darkness from SCG NE โ†’ melatonin synthesis). Jet lag, shift work disorder. (8) Mammillary bodies โ€” memory (limbic); lesion in Wernicke (acute thiamine def โ€” confusion + ataxia + ophthalmoplegia) โ†’ Korsakoff (chronic โ€” anterograde amnesia + confabulation; haemorrhage + atrophy of mammillary bodies pathognomonic). Hypothalamic-pituitary axis: (a) Anterior pituitary (adenohypophysis) โ€” Rathke's pouch origin (oral ectoderm); receives releasing/inhibiting hormones via hypophyseal portal system (median eminence โ€” โ†“ portal veins โ†’ anterior pituitary capillaries). 6 main hormones (mnemonic "FLAT PiG"): FSH (gonadotropin) + LH + ACTH + TSH + PRL (prolactin) + GH (growth hormone). (b) Posterior pituitary (neurohypophysis) โ€” neural ectoderm origin; axonal extension from SON/PVN; stores + releases ADH + oxytocin. Hypothalamic releasing/inhibiting hormones: TRH โ†’ TSH + PRL; CRH โ†’ ACTH; GnRH โ†’ FSH + LH (pulsatile โ€” exogenous GnRH agonist constant suppresses; GnRH antagonist immediate suppression โ€” for prostate cancer, fibroids, IVF, precocious puberty); GHRH โ†’ GH; somatostatin (SST) inhibits GH + TSH; dopamine (PIF) inhibits PRL (D2 antagonist antipsychotic โ†’ hyperprolactinaemia). Pituitary disorders: (a) Acromegaly (GH excess in adult โ€” pituitary adenoma) โ€” broad features, ring/shoe size โ†‘, sleep apnoea, DM, HT, cardiomyopathy. Tx: trans-sphenoidal surgery; somatostatin analogues (octreotide, lanreotide, pasireotide); GH receptor antagonist (pegvisomant); cabergoline. Gigantism = pre-pubertal GH excess. (b) GH deficiency โ€” short stature; recombinant somatropin SC. (c) Cushing disease (ACTH-secreting adenoma) โ€” central obesity + moon face + buffalo hump + striae + HT + DM + osteoporosis + immunosuppression. Tx: surgery; ketoconazole/metyrapone/mitotane/osilodrostat; pasireotide; mifepristone (GR antagonist). (d) Prolactinoma โ€” most common pituitary tumour; galactorrhoea + amenorrhoea + โ†“ libido + infertility. Tx: dopamine agonists (cabergoline first-line; bromocriptine alternative). (e) Hypopituitarism / Sheehan syndrome (postpartum pituitary infarction). (f) SIADH (excess ADH) โ€” hyponatraemia (euvolaemic). Tx: fluid restriction; hypertonic saline if severe; vaptans (tolvaptan, conivaptan โ€” V2 antagonist aquaretic); demeclocycline historical. (g) Diabetes Insipidus (DI): central (โ†“ ADH from pituitary โ€” head trauma, surgery, tumour, idiopathic, autoimmune; tx: desmopressin DDAVP โ€” V2 selective) vs nephrogenic (kidney unresponsive; lithium chronic, hypercalcaemia, hypokalaemia, hereditary AVPR2/AQP2 mutation; tx: thiazide paradoxical, indomethacin, low-Na low-protein diet). Polyuria + polydipsia. Distinguish with water deprivation test + DDAVP challenge.
โœ˜ A wrong: Sensory = thalamus.
โœ˜ C wrong: Motor = motor cortex/BG/cerebellum.
โœ˜ D wrong: Vision = occipital cortex.
17
CSF (cerebrospinal fluid) is produced by: GPAT 2016

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: CSF = clear fluid bathing brain + spinal cord; cushions, regulates ICP, removes waste, glymphatic clearance during sleep. Production: choroid plexus (modified ependymal epithelium + fenestrated capillaries; in lateral ventricles primarily, also 3rd + 4th); ~ 500 mL/day produced + reabsorbed (volume turns over 3-4ร— per day); total volume 125-150 mL. Composition: low protein (15-45 mg/dL โ€” mostly albumin), low glucose (~ 2/3 plasma; 50-80 mg/dL), low Caยฒโบ + K+, slightly higher Mgยฒโบ + Clโป, isotonic. Pressure: 5-15 cmHโ‚‚O / 70-180 mmHโ‚‚O recumbent (LP). CSF circulation: lateral ventricles โ†’ foramina of Monro (interventricular) โ†’ 3rd ventricle โ†’ cerebral aqueduct (of Sylvius) โ†’ 4th ventricle โ†’ exits via foramen of Magendie (median) + 2 foramina of Luschka (lateral) โ†’ subarachnoid space (cerebral + spinal) โ†’ reabsorbed via arachnoid villi/granulations into superior sagittal sinus โ†’ venous circulation. Some via lymphatic drainage (recently characterised meningeal lymphatics). Hydrocephalus = โ†‘ CSF causing ventricular enlargement: (a) Communicating (no ventricular obstruction) โ€” โ†“ absorption (post-meningitis, post-SAH), โ†‘ production (rare choroid plexus papilloma); includes Normal Pressure Hydrocephalus (NPH) โ€” Hakim triad "wet, wobbly, wacky" (urinary incontinence + gait apraxia/magnetic + dementia); ventricles large but pressure normal; treatable with ventriculoperitoneal (VP) shunt. (b) Non-communicating / obstructive โ€” blockage in ventricular system: aqueductal stenosis (most common congenital), Chiari malformation, tumour (colloid cyst 3rd ventricle, posterior fossa tumour blocking 4th), Dandy-Walker malformation. Treatment: VP shunt; endoscopic third ventriculostomy (ETV โ€” alternative for aqueductal stenosis avoiding shunt complications). Lumbar puncture (LP): at L3-L4 or L4-L5 (below conus medullaris L1-L2 in adult; L3 in neonate); landmarks โ€” Tuffier's line / iliac crest = L4. Indications: meningitis, SAH (3-tube test for xanthochromia + RBC count drop indicating traumatic vs true), Guillain-Barrรฉ (albuminocytological dissociation โ€” high protein with normal/low cells), MS (oligoclonal bands), idiopathic intracranial hypertension (BIH/IIH; pseudotumour โ€” papilloedema, headache, obese young women; opening pressure > 25 cmHโ‚‚O), CNS leukaemia/lymphoma (cytology), normal-pressure hydrocephalus (large-volume tap diagnostic + therapeutic). Contraindications: โ†‘ ICP with mass lesion (herniation risk; CT first if focal signs/papilloedema/altered mental status), bleeding diathesis (correct platelet > 50K + INR < 1.5), local skin infection, spinal abnormality. Side effect: post-LP headache (dural leak; bed rest + caffeine + fluid + epidural blood patch if persistent). CSF analysis โ€” clinical: appearance (clear/cloudy/bloody/xanthochromic), opening pressure, cell count + differential (normal < 5 mononuclear; elevated WBC suggests meningitis โ€” bacterial: PMN-predominant + โ†“ glucose + โ†‘ protein; viral: lymphocyte + normal glucose + mildly โ†‘ protein; TB/fungal: lymphocyte + โ†“ glucose + โ†‘ protein); protein; glucose (compare to serum, ratio > 0.6 normal; < 0.4 bacterial); Gram stain + culture + AFB + cryptococcal antigen + India ink + PCR (HSV, enterovirus, etc.); cytology for malignancy; oligoclonal bands MS. BBB (Blood-Brain Barrier): cerebral capillary endothelium tight junctions (claudin-5, occludin, ZO-1) + non-fenestrated + pericytes + astrocyte end-feet glia limitans + low pinocytosis. Permeability: lipid-soluble small (Oโ‚‚, COโ‚‚, ethanol, anaesthetics, lipophilic drugs); transporter-mediated (glucose GLUT1, amino acids LAT1, monocarboxylate MCT1). Excludes most polar/large/charged drugs. Disrupted in stroke, tumour (contrast enhancement), meningitis, MS, sepsis, traumatic brain injury, hypertensive emergency. Circumventricular organs (CVOs) lack BBB: area postrema (vomiting CTZ; senses toxins), OVLT + subfornical organ (osmoreception + thirst + ADH regulation), median eminence (hypothalamic releasing hormones), pineal (melatonin secretion), neurohypophysis (ADH/oxytocin release), choroid plexus (though tight junctions on the apical surface form blood-CSF barrier). Glymphatic system: cerebral lymphatic-like clearance via aquaporin-4 on astrocyte end-feet + perivascular spaces; clears ฮฒ-amyloid + tau + waste; primarily during sleep (20ร— โ†‘ flow); dysfunction in Alzheimer + ageing.
โœ˜ A wrong: Pia is innermost meninx, not CSF source.
โœ˜ B wrong: Arachnoid villi REABSORB CSF.
โœ˜ D wrong: Pineal makes melatonin.
18
Cranial nerves (12 pairs) โ€” mnemonic origin: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: 12 pairs of cranial nerves (CN I-XII). Function mnemonic โ€” "Some Say Marry Money But My Brother Says Big Brains Matter More" (S = sensory, M = motor, B = both): CN I Olfactory (S โ€” smell; only PNS-to-CNS bypassing thalamus). CN II Optic (S โ€” vision; actually CNS extension/tract). CN III Oculomotor (M โ€” SR/IR/MR/IO/LPS muscles + parasympathetic to pupillary sphincter via Edinger-Westphal โ†’ ciliary ganglion โ†’ constriction + accommodation; nerve compression by aneurysm/tumour first affects parasympathetic outer fibres โ†’ blown pupil; ischaemia DM โ†’ motor inner fibres preserved pupil). CN IV Trochlear (M โ€” superior oblique only โ€” depresses + intorts adducted eye; only nerve from DORSAL brainstem; longest intracranial; only crossed CN; lesion โ†’ diplopia going down stairs/reading + head tilt away from affected side). CN V Trigeminal (B โ€” V1 ophthalmic + V2 maxillary + V3 mandibular; sensory face/scalp/anterior tongue/cornea/sinuses + motor muscles of mastication V3 โ€” masseter, temporalis, medial + lateral pterygoids; largest CN; trigeminal neuralgia "tic douloureux" โ€” paroxysmal stabbing facial pain โ€” tx: carbamazepine first-line, oxcarbazepine, baclofen, gabapentin, surgical microvascular decompression). CN VI Abducens (M โ€” lateral rectus only โ€” abducts eye; longest intracranial course โ†’ vulnerable in โ†‘ ICP "false localising sign"). CN VII Facial (B โ€” facial expression + stapedius + taste anterior 2/3 tongue chorda tympani + parasympathetic to lacrimal + sublingual + submandibular glands; Bell palsy โ€” idiopathic LMN VII paralysis โ€” sudden unilateral facial droop including forehead + ear pain + hyperacusis + ageusia; UMN lesion spares forehead โ€” bilateral cortical innervation of upper face; tx: prednisone within 72 h ยฑ acyclovir; usually full recovery 70-80 %). CN VIII Vestibulocochlear (Auditory) (S โ€” hearing + balance). CN IX Glossopharyngeal (B โ€” taste posterior 1/3 tongue + sensation pharynx + middle ear + parotid parasympathetic + carotid sinus baroreceptor + chemoreceptor + stylopharyngeus muscle motor). CN X Vagus (B โ€” longest CN; "wandering" nerve; thoracic + abdominal viscera parasympathetic to splenic flexure; palate + pharynx + larynx motor + sensory; aortic arch baro/chemo; 75 % of all parasympathetic; recurrent laryngeal nerve loops under aortic arch left + subclavian right โ€” vulnerable in thoracic surgery + aortic aneurysm; vagal nerve stimulation FDA-approved for refractory epilepsy + depression + recently for inflammation). CN XI Spinal Accessory (M โ€” sternocleidomastoid + trapezius โ€” head rotation + shoulder shrug). CN XII Hypoglossal (M โ€” tongue muscles except palatoglossus โ€” XII innervates intrinsic + most extrinsic; XI palatoglossus is exception via vagus). Cranial nerve foramina exit: cribriform plate (I); optic canal (II); superior orbital fissure (III, IV, V1, VI; SOF is gateway); foramen rotundum (V2); foramen ovale (V3); internal acoustic meatus (VII, VIII); jugular foramen (IX, X, XI); hypoglossal canal (XII). Cranial nerve nuclei locations: midbrain (III, IV); pons (V โ€” main sensory + motor + spinal trigeminal nucleus + mesencephalic nucleus, VI, VII, VIII); medulla (IX, X, XI, XII; nucleus ambiguus + dorsal motor of vagus + nucleus tractus solitarius + hypoglossal). Cranial nerves examined systematically I-XII; reflexes tested (corneal V1+VII; pupillary II+III; gag IX+X; jaw jerk V).
โœ˜ B wrong: 12 pairs not 10.
โœ˜ C wrong: 12 not 13.
โœ˜ D wrong: Mnemonic exists.
19
Resting membrane potential of typical neuron: GPAT 2017

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Neuron resting membrane potential (RMP) ~ โˆ’70 mV; muscle ~ โˆ’90; cardiac contractile โˆ’90; SA node โˆ’60; smooth muscle โˆ’55. RMP determined by: (1) Ion concentration gradients established by Na+/K+ ATPase (3 Na+ out / 2 K+ in per ATP โ€” electrogenic, contributes ~ โˆ’10 mV directly); (2) Differential membrane permeability โ€” K+ leak channels (P_K >> P_Na ~ 100:1 at rest) โ†’ Vm approaches E_K. Nernst equation (equilibrium potential for single ion at 37 ยฐC body temp): E_ion = (61/z) ร— log([out]/[in]) mV. E_K ~ โˆ’90 mV (intracell K 140, extracell 4 mM); E_Na ~ +60 mV (intracell 14, extracell 142); E_Cl ~ โˆ’70 mV (intracell 10, extracell 110); E_Ca ~ +125 mV (intracell 100 nM, extracell 2.5 mM โ€” 10000-fold gradient). Goldman-Hodgkin-Katz (GHK) equation: actual Vm considering multiple ions weighted by permeability. Action potential phases (Hodgkin-Huxley 1952; squid giant axon): (1) Resting (~ โˆ’70 mV; K+ leak dominant). (2) Local depolarisation to threshold ~ โˆ’55 mV (positive feedback voltage-gated Na+ channel activation). (3) Depolarisation (rapid; voltage-gated Na+ channels open โ†’ massive Na+ influx โ†’ Vm overshoots toward E_Na to ~ +40 mV). (4) Repolarisation (Na+ channels INACTIVATE within ~ 1 ms; voltage-gated K+ channels open with delay = "delayed rectifier" โ†’ K+ efflux). (5) Hyperpolarisation (undershoot) โ€” K+ channels close slowly; Vm transiently more negative than rest. (6) Na+/K+ ATPase restores ion gradients (slow background; doesn't cause AP โ€” gradient existed before). All-or-none law. Refractory periods: (a) Absolute โ€” Na+ channels inactivated; no AP regardless of stimulus; ~ 1-2 ms; ensures unidirectional propagation. (b) Relative โ€” some Na+ recovered + K+ still open; AP possible with suprathreshold stimulus. Conduction velocity: โˆ axon diameter ร— โˆšmyelination. Aฮฑ motor + Ia muscle spindle largest 12-20 ฮผm myelinated โ†’ ~ 70-120 m/s. C unmyelinated 0.5-2 ฮผm โ†’ 0.5-2 m/s (slow pain). Saltatory conduction: in myelinated axons, AP "jumps" between nodes of Ranvier (where Na+ channels concentrated; internodes have fewer); much faster + energy-efficient. Demyelinating diseases: MS (CNS โ€” oligodendrocyte attack; relapsing-remitting/progressive; tx: interferon, glatiramer, fingolimod, teriflunomide, dimethyl fumarate, natalizumab, ocrelizumab, alemtuzumab, cladribine, ofatumumab, ublituximab, BTKi); GBS (PNS โ€” Schwann cell; ascending paralysis after Campylobacter or other infection; tx: IVIG or plasmapheresis, supportive ventilation if respiratory failure); CIDP (chronic inflammatory demyelinating polyneuropathy; chronic GBS-equivalent; IVIG/plasmapheresis/steroids); Charcot-Marie-Tooth (hereditary; demyelinating CMT1 vs axonal CMT2; PMP22 most common). Cardiac AP differences: SA node phase 4 spontaneous depolarisation by funny current I_f (HCN channel โ€” Na+ + K+; ฮฒ1 โ†‘ I_f โ†’ โ†‘ HR; M2 โ†“ I_f โ†’ โ†“ HR); phase 0 by L-type Caยฒโบ (no fast Na+ in nodal); ventricular myocardium has plateau phase 2 (Caยฒโบ in via L-type balanced by K+ out) โ†’ long ARP ~ 250 ms (no tetany; protects against re-entry). Long QT syndrome: prolonged repolarisation; risk torsades. Ion channel toxins: tetrodotoxin (TTX, puffer fish/Fugu), saxitoxin (paralytic shellfish poisoning) โ€” block extracellular Na+ channels โ†’ flaccid paralysis + respiratory failure; no antidote, supportive ventilation; LD50 TTX ~ 1 ฮผg/kg (one of most lethal natural toxins). Local anaesthetics (lidocaine, bupivacaine, procaine) block Na+ channels intracellularly in inactivated state. Tetraethylammonium (TEA) blocks K+. Calcium channel blockers (verapamil, diltiazem, dihydropyridines โ€” amlodipine, nifedipine).
โœ˜ A wrong: 0 mV not viable.
โœ˜ C wrong: +40 = AP peak transient.
โœ˜ D wrong: Too negative.
20
EEG (electroencephalogram) waves: Practice Question

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: EEG records summed cortical electrical activity from scalp electrodes (10-20 international system: Fp1, Fp2, F3, F4, etc.). Wave types by frequency: Gamma (30+ Hz, often 30-100) โ€” high cognitive function, perception binding, attention. Beta (13-30 Hz, low amplitude) โ€” alert wakefulness, active concentration, busy thinking, anxiety. Alpha (8-13 Hz, prominent posteriorly) โ€” awake, relaxed, eyes closed; disappears with eye opening (alpha desynchronisation/blocking). Theta (4-7 Hz) โ€” drowsy, light sleep N1, meditation, hippocampal memory consolidation, children normal but abnormal in awake adult (suggests pathology โ€” encephalopathy, dementia, anaesthesia). Delta (< 4 Hz, high amplitude) โ€” deep slow-wave sleep N3 (SWS โ€” most restorative); coma; encephalopathy; toddlers' awake. Sleep stages: (a) NREM N1 (5 % โ€” light sleep; theta + slow eye movements; vertex sharp waves); (b) NREM N2 (45 %; sleep spindles + K complexes; thalamocortical; threshold to wake higher); (c) NREM N3 / SWS (25 %; delta dominant; deep sleep; growth hormone secretion peaks; difficult to wake; sleepwalking + night terrors + bedwetting); (d) REM (25 %; rapid eye movement; "paradoxical" sleep โ€” EEG looks awake (beta) but skeletal muscle atonia mediated by glycine; vivid dreams; cycling 90-120 min throughout night with REM periods longer toward morning). Sleep architecture: cycles N1 โ†’ N2 โ†’ N3 โ†’ N2 โ†’ REM ร— 4-6 cycles/night; REM proportion โ†‘ in second half of night. Total sleep need: adult 7-9 h; โ†“ with age; child + teenagers 8-12 h. Sleep disorders: (1) Insomnia โ€” most common; treatment: sleep hygiene + CBT-I (first-line) + short-term hypnotics (zolpidem, eszopiclone, zaleplon โ€” Z-drugs; melatonin agonists ramelteon; orexin antagonists suvorexant, lemborexant, daridorexant; trazodone โ€” off-label; low-dose doxepin โ€” H1 antagonist; benzodiazepines short-term). (2) Obstructive sleep apnoea (OSA) โ€” pharyngeal collapse with snoring + apnoeas + daytime somnolence; STOP-BANG screening; polysomnography (AHI > 5 mild, > 15 moderate, > 30 severe); CPAP first-line; mandibular advancement; weight loss; positional. (3) Central sleep apnoea (CHF, opioid, high altitude, brainstem). (4) Narcolepsy โ€” orexin (hypocretin) deficiency; type 1 with cataplexy + low CSF orexin; type 2 without cataplexy. Sleep attacks + cataplexy (sudden muscle weakness with emotion) + sleep paralysis + hypnagogic hallucinations + REM intrusion into wakefulness. Tx: stimulants (modafinil, armodafinil, methylphenidate, dextroamphetamine, solriamfetol); pitolisant (H3 inverse agonist); sodium oxybate (ฮณ-hydroxybutyrate GHB; for cataplexy); antidepressants (REM suppression โ€” TCAs, SSRIs, venlafaxine for cataplexy). (5) Restless Legs Syndrome (RLS) / Willis-Ekbom disease โ€” urge to move legs, worse evening + rest, relief with movement; iron deficiency association (ferritin < 75 โ†’ supplement); dopamine agonists (pramipexole, ropinirole, rotigotine โ€” beware augmentation), ฮฑ2ฮด ligands (gabapentin enacarbil, pregabalin), opioids (refractory). (6) Periodic Limb Movement Disorder (PLMD). (7) REM Sleep Behavior Disorder (RBD) โ€” loss of REM atonia โ†’ act out dreams; antecedent of ฮฑ-synucleinopathies (Parkinson, DLB, MSA โ€” RBD is preclinical marker). Tx: melatonin first-line, clonazepam alternative; environment safety (move sharp objects, padded floor). (8) Sleep paralysis + hypnagogic hallucinations. (9) Parasomnias: NREM (sleepwalking, night terrors, sleep eating) + REM (RBD, nightmares). (10) Circadian rhythm disorders: delayed/advanced sleep phase, jet lag, shift work, non-24-hour (blind). EEG clinical use: (a) Epilepsy (interictal spikes, seizure capture, characterise โ€” generalised vs focal); (b) Encephalopathy (slowing); (c) Anoxic brain injury post-cardiac arrest (prognostic โ€” myoclonic status, burst-suppression); (d) Brain death assessment (electrocerebral silence โ€” ECS); (e) Sleep monitoring (PSG); (f) Anaesthesia depth monitoring (BIS โ€” bispectral index 0-100); (g) Coma evaluation; (h) Locked-in syndrome differential. (i) Status epilepticus management. Continuous EEG monitoring in NICU/ICU.
โœ˜ B wrong: Heart = ECG.
โœ˜ C wrong: Muscle = EMG.
โœ˜ D wrong: Apnoea by polysomnography.

๐Ÿ“Œ Unit I โ€” High-Yield Points (Print-Ready)

  1. CNS organisation: Brain (1400 g, 86 billion neurons) + spinal cord. Protected by skull/vertebrae + 3 meninges (dura/arachnoid/pia) + CSF (~150 mL; choroid plexus 500 mL/day; LV โ†’ Monro โ†’ 3rd โ†’ aqueduct โ†’ 4th โ†’ Magendie/Luschka โ†’ SAS โ†’ arachnoid villi โ†’ sagittal sinus) + BBB (tight junctions claudin-5/occludin + pericytes + astrocyte end-feet). Brain regions: Cerebrum (4 lobes โ€” frontal motor M1+Broca, parietal sensory S1+spatial, temporal auditory+Wernicke+memory hippocampus, occipital vision V1; corpus callosum); Cerebellum (motor coordination IPSILATERAL; lesion DANISH โ€” Dysmetria/Ataxia/Nystagmus/Intention tremor/Scanning speech/Hypotonia; alcoholism vermis; PICA AICA SCA strokes; Friedreich); Basal ganglia (caudate+putamen=striatum / GPi+GPe / STN / SNc-SNr; direct D1+ vs indirect D2โˆ’ pathways; Parkinson SNc DA loss TRAP+Lewy bodies; Huntington CAG-HTT caudate atrophy chorea+dementia+psych; Wilson Cu-ATP7B+KF rings; hemiballismus STN); Brainstem (midbrain CN III/IV+SN+red nucleus; pons CN V/VI/VII/VIII+pneumo+apneu; medulla CN IX/X/XI/XII+vital cardio-respiratory-vomiting+pyramidal decussation); Diencephalon (thalamus sensory relay + hypothalamus master homeostat + epithalamus pineal+habenula); Limbic (hippocampus memory + amygdala emotion + cingulate + mammillary bodies โ€” Korsakoff). Spinal cord ends L1-L2 conus medullaris; cauda equina; LP L3-L4/L4-L5; 31 spinal nerves (8C+12T+5L+5S+1Co). Tracts: DCML fine touch+vibration+proprioception (cuneatus upper/gracilis lower; decussates lower medulla); Spinothalamic pain+temp+crude touch (decussates at cord level); Lateral corticospinal motor (decussates lower medulla 85%). Brown-Sรฉquard ipsilateral DCML+motor + contralateral pain/temp.
  2. ANS: Sympathetic T1-L2 thoracolumbar โ€” short pre-ganglionic AChโ†’N_N nicotinic ganglion + long post-ganglionic NEโ†’ฮฑ/ฮฒ (except sweat M3 cholinergic; adrenal medulla = modified ganglion releases 80 % epi+20 % NE direct to blood). ฮฑ1 vasoconstriction+mydriasis+GU sphincter (Gq); ฮฑ2 pre-syn โ†“NE (Gi); ฮฒ1 cardiac โ†‘HR/contractility/renin (Gs); ฮฒ2 bronchodil+vasodil skel/coron+glycogenolysis+uterine relax (Gs); ฮฒ3 lipolysis+bladder relax. Parasympathetic craniosacral CN III/VII/IX/X + S2-S4 โ€” long pre-gang AChโ†’N_N + short post-gang AChโ†’M1-M5. M1 CNS+gastric; M2 cardiac โ†“HR (Gi); M3 smooth m+gland+pupil constriction (Gq); M4-M5 CNS. Vagus = 75 % parasympathetic; thoracoabdominal to splenic flexure. Enteric NS Auerbach motility+Meissner secretion (autonomous). Receptors + pharmacology โ€” ฮฑ1-blockers prazosin/tamsulosin BPH; ฮฑ2 agonists clonidine/methyldopa HT; ฮฒ-blockers selective ฮฒ1 metoprolol/atenolol/bisoprolol/nebivolol vs non-selective propranolol vs ฮฑ+ฮฒ labetalol/carvedilol; sympathomimetics IM-anaphylaxis adrenaline 1:1000 0.3-0.5 mg + IV cardiac arrest 1:10000 1 mg; ฮฒ2 SABA salbutamol asthma; muscarinic agonists pilocarpine glaucoma+Sjรถgren+bethanechol urinary retention; AChE inhibitors physostigmine (BBB anticholinergic OD), neostigmine/pyridostigmine MG+NMBA reversal, donepezil/rivastigmine/galantamine Alzheimer; muscarinic antagonists atropine+scopolamine TD+ipratropium+tiotropium+oxybutynin/tolterodine OAB+benztropine PD+glycopyrrolate; nicotinic blockers ganglion (trimethaphan obsolete) + NMJ non-depolarising tubocurarine/atracurium/rocuronium reversed by neostigmine/sugammadex + depolarising succinylcholine.
  3. Synapses + neurotransmitters: Reflex arc 5 components โ€” receptor โ†’ afferent โ†’ integration centre โ†’ efferent โ†’ effector. Stretch reflex monosynaptic (knee L3-L4, biceps C5-C6, triceps C7-C8, ankle S1-S2; Ia afferent โ†’ ฮฑ-motor); inverse stretch via GTO Ib autogenic inhibition; withdrawal polysynaptic with crossed extensor; Babinski plantar โ€” extensor abnormal > 2 yr (UMN). Synaptic transmission: AP โ†’ VG-Caยฒโบ โ†’ vesicle SNARE fusion (botulinum cleaves SNAP-25 โ†’ flaccid; tetanus toxin cleaves at central inhibitory neurons โ†’ spastic) โ†’ NT release โ†’ receptor binding โ†’ EPSP/IPSP โ†’ summation at axon hillock โ†’ AP if threshold; termination โ€” reuptake (SERT/NET/DAT/GAT/GLT) + enzyme (AChE, MAO, COMT) + diffusion. NTs: Glutamate major excitatory (AMPA/NMDA/kainate ionotropic + 8 mGluR; excitotoxicity stroke); GABA major inhibitory brain (A ionotropic Clโป โ€” BZD โ†‘ frequency, barbiturates โ†‘ duration, alcohol; B metabotropic Gi โ€” baclofen spasticity); glycine inhibitory cord/brainstem (strychnine antagonist) + co-agonist NMDA; dopamine 4 pathways (nigrostriatal motor PD; mesolimbic reward+positive psychotic; mesocortical cognition+negative; tuberoinfundibular PRL inhibition); serotonin raphe (mood, sleep, appetite, vomiting CTZ; SSRI/SNRI/MAOi/TCA); NE locus coeruleus (attention/arousal); histamine tuberomamillary (wakefulness; H1 sedation); ACh nucleus basalis (memory, Alzheimer loss); opioids endo/enkephalin/dynorphin ฮผ/ฮด/ฮบ; neuropeptides (substance P pain, CCK, VIP, somatostatin, NPY, ghrelin, leptin). RMP โˆ’70 mV (K+ leak + Na/K ATPase; Nernst E_K โˆ’90, E_Na +60); AP threshold โˆ’55, peak +40, ARP/RRP; saltatory in myelinated; demyelinating MS (CNS) + GBS (PNS); ion channel toxins TTX/saxitoxin Na+ block. EEG: gamma 30+ cognition, beta >13 alert, alpha 8-13 relaxed eyes closed, theta 4-7 drowsy, delta <4 SWS deep sleep. NREM N1/N2/N3 + REM (atonia + dreams).
  4. Special senses: Vision: cornea (43 D refraction) + lens (16 D variable accommodation) + retina layers RPEโ†’photoreceptorโ†’outer nuclearโ†’outer plexiformโ†’inner nuclear (bipolar/horizontal/amacrine/Mรผller)โ†’inner plexiformโ†’ganglionโ†’optic nerve. Rods (120M; rhodopsin opsin+11-cis-retinal; dim/scotopic peripheral B/W) + Cones (6M; S/M/L photopsins; bright/photopic foveal colour). Phototransduction โ€” light โ†’ 11-cis to all-trans retinal โ†’ transducin โ†’ PDE โ†’ โ†“cGMP โ†’ CNG closes โ†’ hyperpolarise. Pathway: retina โ†’ CN II โ†’ optic chiasm (nasal cross) โ†’ optic tract โ†’ LGN โ†’ optic radiations (Meyer/parietal) โ†’ V1 calcarine. Pupillary reflex CN II afferent + CN III efferent; near triad accommodation (ciliary contracts โ†’ zonules slacken โ†’ lens convex via M3 parasympathetic) + miosis + convergence. Refractive errors myopia/hyperopia/astigmatism/presbyopia (post-40 lens elasticity loss). Glaucoma โ†‘IOPโ†’ON damage (tx ฮฒ-blocker timolol/PG analog latanoprost/ฮฑ2 brimonidine/CAI dorzolamide/miotic pilocarpine). Cataract lens opacity. AMD (dry drusen+atrophy/wet anti-VEGF intravitreal). Diabetic retinopathy. Retinal detachment emergent. Hearing: external (pinna+EAM+TM) + middle (MIS Malleus-Incus-Stapes; tensor tympani CN V3+stapedius CN VII; Eustachian tube nasopharynx; oval+round windows) + inner (cochlea 2.5 turns; perilymph scala vestibuli/tympani; endolymph scala media+organ of Corti with inner+outer hair cells+stereocilia+tectorial+basilar membrane; place theory Bรฉkรฉsy high freq base/low apex). Sound: TM โ†’ ossicles 22ร— amplification โ†’ oval window โ†’ fluid wave โ†’ basilar membrane โ†’ hair cell deflection โ†’ CN VIII โ†’ cochlear nuclei โ†’ SOL โ†’ IC โ†’ MGN thalamus โ†’ A1 Heschl. Conductive (Rinne BC>AC affected; Weber lateralises to affected) vs SNHL (Rinne AC>BC; Weber away affected; presbycusis, noise, ototoxic โ€” aminoglycoside/cisplatin/loop/salicylate). Cochlear implant for severe SNHL bilateral. Vestibular: utricle+saccule otoliths linear+gravity; 3 semicircular canals angular acceleration via cupula. VOR. BPPV (Dix-Hallpike +; Epley repositioning); Mรฉniรจre (endolymphatic hydrops; vertigo+SNHL+tinnitus+fullness; low-Na+diuretic+intratympanic gent); vestibular neuritis (acute viral; days; vestibular sedatives short-term then rehab); vestibular schwannoma CN VIII (NF2 bilateral). Vestibular suppressants: meclizine/dimenhydrinate/scopolamine TD/diazepam/ondansetron โ€” short-term only. Taste: 5 โ€” sweet T1R2/3, umami T1R1/3 (glutamate/IMP/GMP), bitter T2R, sour H+, salty Na+ ENaC; CN VII anterior 2/3 + IX posterior 1/3 + X epiglottis โ†’ NTS โ†’ VPM โ†’ insula. Filiform no taste; fungiform/circumvallate/foliate have taste buds. Smell: olfactory epithelium โ†’ CN I (only sensory bypassing thalamus) โ†’ cribriform plate โ†’ bulb โ†’ tract โ†’ piriform/entorhinal/amygdala (limbic). 350 olfactory genes. Anosmia COVID/PD/AD early sign; olfactory training. Skin: Meissner light touch flutter; Pacinian deep pressure+vibration; Ruffini stretch+warm; Merkel sustained light touch+texture; free nerve endings pain (Aฮด sharp+C burning)+itch+temp (TRPV1 hot/capsaicin, TRPM8 cold/menthol, TRPA1 mustard/wasabi).
  5. Hypothalamus + pituitary + cranial nerves: Hypothalamus master regulator (HEAL TAN โ€” Hormones+Eating/Autonomic+Libido+Thermoregulation+Adrenergic+Neurosecretion). Nuclei: SON+PVN (ADH+oxytocin โ†’ posterior pit; PVN also CRH+TRH); arcuate (GHRH/GnRH/dopamine PIF/NPY-AgRP orexigenic+POMC anorexigenic โ€” leptin); anterior+preoptic heat dissipation; posterior heat conservation; lateral hunger orexin (loss โ†’ narcolepsy); ventromedial satiety; SCN circadian (light via melanopsin RGC); mammillary memory (Wernicke-Korsakoff thiamine def haemorrhage). HPA via portal system: TRHโ†’TSH+PRL; CRHโ†’ACTH; GnRHโ†’FSH+LH (pulsatile); GHRHโ†’GH; SST inhibits GH+TSH; DA inhibits PRL. Anterior pit ("FLAT PiG" FSH/LH/ACTH/TSH/PRL/GH); posterior pit ADH+oxytocin. Disorders: acromegaly (GH excess; trans-sphenoidal surgery+octreotide+pegvisomant+cabergoline), Cushing disease (ACTH adenoma), prolactinoma (cabergoline first), Sheehan postpartum, hypopituitarism, SIADH (fluid restrict+vaptans), DI central (DDAVP) vs nephrogenic (thiazide+indomethacin). 12 cranial nerves โ€” mnemonic "On Old Olympus..."; "Some Say Marry Money But My Brother Says Big Brains Matter More". CN I olfactory (S, bypass thalamus), II optic (S; CNS tract), III oculomotor (M+parasym pupil/accomm โ€” aneurysm blown pupil first), IV trochlear (M, SO; only dorsal+crossed; longest intracranial; head tilt), V trigeminal (B; V1/V2/V3; mastication + sensation; trigeminal neuralgia carbamazepine), VI abducens (M, LR; longest course โ†’ false localising in โ†‘ICP), VII facial (B; expression+stapedius+anterior 2/3 taste chorda tympani+lacrimal/sublingual/submandibular parasym; Bell palsy LMN spares forehead in UMN โ€” bilateral cortical innervation upper face; tx prednisone+acyclovir), VIII vestibulocochlear (S; hearing+balance), IX glossopharyngeal (B; post 1/3 taste+pharynx sensation+parotid parasym+carotid sinus/body+stylopharyngeus), X vagus (B; longest; thoracoabdominal to splenic flexure+palate/pharynx/larynx; recurrent laryngeal under arch left/subclavian right); XI spinal accessory (M; SCM+trapezius), XII hypoglossal (M; tongue except palatoglossus = X). Foramina: cribriform I; optic canal II; SOF III/IV/V1/VI; rotundum V2; ovale V3; IAM VII/VIII; jugular IX/X/XI; hypoglossal canal XII.
UNIT II
Digestive System ยท Energy Metabolism ยท BMR ยท Vitamins (Q21 โ€“ Q40)
21
Which enzyme of the salivary glands initiates the digestion of starch? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Salivary ฮฑ-amylase (ptyalin) is secreted by the parotid gland; it hydrolyses ฮฑ-1,4 glycosidic bonds of starch into maltose, maltotriose and ฮฑ-limit dextrins. Its optimum pH is ~ 6.8 and it is inactivated by gastric HCl in the stomach.
โœ˜ A wrong: Lingual lipase digests triglycerides, not starch.
โœ˜ B wrong: Pepsin digests proteins in the stomach.
โœ˜ D wrong: Trypsin is a pancreatic protease.
22
The intrinsic factor required for vitamin B12 absorption is secreted by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Parietal cells of gastric glands secrete both HCl and intrinsic factor (IF). IF binds vitamin B12 and is essential for its absorption in the terminal ileum. Loss of parietal cells (autoimmune gastritis) โ†’ IF deficiency โ†’ pernicious anaemia.
โœ˜ A wrong: Chief cells secrete pepsinogen.
โœ˜ C wrong: G cells secrete gastrin.
โœ˜ D wrong: Mucous cells secrete mucus.
23
Which of the following hormones stimulates gallbladder contraction and pancreatic enzyme secretion? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: CCK is released from I-cells of the duodenum/jejunum in response to fat and protein. It contracts the gallbladder, relaxes the sphincter of Oddi and stimulates pancreatic enzyme (zymogen) secretion. It also delays gastric emptying.
โœ˜ B wrong: Secretin stimulates pancreatic bicarbonate (alkaline) secretion.
โœ˜ C wrong: Gastrin stimulates gastric acid secretion.
โœ˜ D wrong: Motilin governs migrating motor complex.
24
The pH of normal gastric juice is approximately: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Gastric juice has a pH of 1 โ€“ 2 (highly acidic) because of HCl secreted by parietal cells. This activates pepsinogen โ†’ pepsin, kills ingested microorganisms, and provides optimum pH for pepsin activity.
โœ˜ A wrong: Too alkaline for gastric juice.
โœ˜ B wrong: Too high; not characteristic of fasting gastric juice.
โœ˜ C wrong: Closer but typical fasting pH is below 2.
25
The principal site of absorption of dietary fats is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Most fat absorption occurs in the jejunum after emulsification by bile salts and digestion by pancreatic lipase. Monoglycerides and free fatty acids form micelles, diffuse into enterocytes, are re-esterified, packaged into chylomicrons, and enter lacteals.
โœ˜ A wrong: Stomach mainly digests proteins; minimal fat absorption.
โœ˜ B wrong: Duodenum absorbs iron, calcium; partial fat absorption.
โœ˜ D wrong: Ileum absorbs vitamin B12 and bile salts.
26
Bile salts emulsify fats in the small intestine. They are synthesized in the liver from: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Primary bile acids (cholic acid, chenodeoxycholic acid) are synthesised from cholesterol via 7ฮฑ-hydroxylase (rate-limiting step). Conjugation with glycine/taurine forms bile salts which emulsify dietary fat. ~ 95 % is reabsorbed in the terminal ileum (enterohepatic circulation).
โœ˜ A wrong: Triglycerides are dietary fat substrates, not bile salt precursors.
โœ˜ C wrong: Phospholipids stabilise micelles but are not converted to bile salts.
โœ˜ D wrong: Bilirubin is a heme breakdown product excreted via bile.
27
Which of the following is NOT a function of the liver? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Insulin is produced by ฮฒ-cells of the pancreatic Islets of Langerhans, NOT by the liver. The liver performs ~ 500 functions including detoxification (Phase I/II metabolism), bile production, plasma protein synthesis (albumin, clotting factors), glycogenolysis, gluconeogenesis, lipid metabolism and vitamin storage (A, D, B12).
โœ˜ B wrong: Liver is the primary site of drug metabolism.
โœ˜ C wrong: Hepatocytes synthesise albumin (~ 12 g/day).
โœ˜ D wrong: Liver stores ~ 100 g of glycogen.
28
The basal metabolic rate (BMR) is measured under conditions of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: BMR is the minimum energy required to maintain vital functions (cardiac output, respiration, basal cellular metabolism) measured under standard conditions: subject awake but at complete rest, mentally relaxed, after a 12-h fast (post-absorptive), and in a thermoneutral environment (no shivering/sweating). Normal adult ~ 1 kcal/kg/h (โ‰ˆ 1500 โ€“ 1800 kcal/day).
โœ˜ A wrong: Exercise increases metabolic rate above basal.
โœ˜ B wrong: Specific dynamic action elevates rate after meals.
โœ˜ C wrong: Sleep further lowers metabolic rate ~ 10 % below basal.
29
Which of the following hormones increases BMR most prominently? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Thyroid hormones are the principal calorigenic hormones โ€” they โ†‘ Naโบ/Kโบ ATPase activity, โ†‘ mitochondrial oxygen consumption and uncouple oxidative phosphorylation. Hyperthyroidism โ†‘ BMR up to + 100 %; hypothyroidism โ†“ BMR by 30 โ€“ 40 %.
โœ˜ A wrong: Insulin promotes anabolism but does not significantly alter BMR.
โœ˜ B wrong: Cortisol has minor catabolic effect; modest BMR rise only at high doses.
โœ˜ D wrong: Aldosterone regulates Naโบ/Kโบ balance, not metabolic rate.
30
The respiratory quotient (RQ) for pure carbohydrate oxidation is: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: RQ = COโ‚‚ produced / Oโ‚‚ consumed. For carbohydrate (Cโ‚†Hโ‚โ‚‚Oโ‚† + 6Oโ‚‚ โ†’ 6COโ‚‚ + 6Hโ‚‚O), RQ = 6/6 = 1.0. For fat โ‰ˆ 0.7, for protein โ‰ˆ 0.8. Mixed diet RQ is ~ 0.85.
โœ˜ B wrong: 0.8 is RQ for proteins.
โœ˜ C wrong: 0.7 is RQ for fats.
โœ˜ D wrong: No physiological substrate gives 0.5.
31
Vitamin K is essential for the ฮณ-carboxylation of clotting factors: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Vitamin K acts as a cofactor for ฮณ-glutamyl carboxylase that converts glutamate residues to ฮณ-carboxyglutamate (Gla) in factors II (prothrombin), VII, IX, X and proteins C, S, Z. Warfarin antagonises vitamin K epoxide reductase (VKORC1) โ†’ โ†“ active clotting factors โ†’ anticoagulation.
โœ˜ A wrong: These are not vitamin K-dependent.
โœ˜ C wrong: Factor III is tissue factor; not vitamin K dependent.
โœ˜ D wrong: VIII, XI, XII are not vitamin K dependent.
32
Which vitamin deficiency causes night blindness (nyctalopia)? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Vitamin A (retinal) combines with opsin to form rhodopsin in rods โ€” essential for vision in dim light. Deficiency โ†’ night blindness (early sign), Bitot's spots, xerophthalmia, keratomalacia. RDA ~ 600 ยตg retinol equivalents/day.
โœ˜ A wrong: B12 deficiency โ†’ megaloblastic anaemia, neurological symptoms.
โœ˜ B wrong: Vitamin D deficiency โ†’ rickets/osteomalacia.
โœ˜ D wrong: Vitamin K deficiency โ†’ bleeding disorders.
33
Beriberi is caused by deficiency of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Thiamine (B1) deficiency causes beriberi โ€” wet beriberi (high-output cardiac failure, oedema), dry beriberi (peripheral neuropathy) and Wernicke-Korsakoff syndrome (alcoholics โ€” confusion, ophthalmoplegia, ataxia, amnesia). Thiamine pyrophosphate (TPP) is a cofactor for pyruvate dehydrogenase, ฮฑ-KGDH and transketolase.
โœ˜ B wrong: B2 deficiency โ†’ cheilosis, glossitis, angular stomatitis.
โœ˜ C wrong: B3 deficiency โ†’ pellagra (3 D's).
โœ˜ D wrong: B6 deficiency โ†’ peripheral neuritis, sideroblastic anaemia.
34
Pellagra (4 D's โ€” dermatitis, diarrhoea, dementia, death) is due to deficiency of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Niacin (B3) is a precursor of NADโบ/NADPโบ โ€” coenzymes for > 200 dehydrogenases. Deficiency causes pellagra (3 D's: dermatitis on sun-exposed areas โ€” Casal's necklace, diarrhoea, dementia; death if untreated โ†’ 4th D). Tryptophan can substitute for niacin (60 mg Trp = 1 mg niacin).
โœ˜ A wrong: Folate deficiency โ†’ megaloblastic anaemia, neural tube defects.
โœ˜ B wrong: Pantothenic acid (B5) deficiency is rare; "burning feet syndrome".
โœ˜ C wrong: Biotin deficiency โ†’ dermatitis, alopecia (egg-white injury).
35
Scurvy is caused by deficiency of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Vitamin C is required for hydroxylation of proline and lysine residues in collagen synthesis (cofactor for prolyl/lysyl hydroxylase). Deficiency โ†’ defective collagen โ†’ swollen bleeding gums, loosening of teeth, perifollicular haemorrhage, poor wound healing, anaemia. RDA = 40 mg/day.
โœ˜ A wrong: Vitamin A deficiency โ†’ night blindness, xerophthalmia.
โœ˜ C wrong: Vitamin D deficiency โ†’ rickets.
โœ˜ D wrong: Vitamin E deficiency โ†’ haemolytic anaemia, neurological symptoms.
36
Active form of vitamin D is: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Cholecalciferol (D3) is hydroxylated at C-25 in the liver โ†’ 25(OH)Dโ‚ƒ (calcidiol โ€” major storage form, used to assess status), then hydroxylated at C-1 in kidney by 1ฮฑ-hydroxylase โ†’ 1,25(OH)โ‚‚Dโ‚ƒ (calcitriol โ€” biologically active form). Calcitriol โ†‘ intestinal Caยฒโบ/POโ‚„ยณโป absorption, โ†‘ bone resorption, โ†‘ renal Ca reabsorption.
โœ˜ A wrong: D3 from skin is inactive precursor.
โœ˜ B wrong: 25(OH)Dโ‚ƒ is intermediate; clinical marker, not active form.
โœ˜ D wrong: D2 from plants requires same activation steps.
37
Specific dynamic action (SDA / thermic effect) is highest for: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: SDA / thermic effect of food is the obligatory energy expenditure for digestion, absorption and assimilation. Proteins have the highest SDA (~ 30 %) due to high cost of deamination, urea synthesis and gluconeogenesis from amino acids. CHO ~ 6 %, fats ~ 4 %, mixed ~ 10 %.
โœ˜ B wrong: CHO SDA is low.
โœ˜ C wrong: Fat SDA is lowest.
โœ˜ D wrong: Mixed diet is intermediate.
38
The largest absorptive surface in the small intestine is provided by: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Surface amplification in the small intestine: plicae circulares ร— 3, villi ร— 10, microvilli ร— 20 โ†’ total โ‰ˆ ร— 600 amplification. Microvilli (1 ยตm) on enterocyte apex contribute the largest fraction of total surface area (~ 200 mยฒ) and contain hydrolytic enzymes (disaccharidases, peptidases).
โœ˜ A wrong: Plicae circulares contribute ~ 3-fold amplification.
โœ˜ C wrong: Villi contribute ~ 10-fold; less than microvilli.
โœ˜ D wrong: Crypts house stem cells & Paneth cells, not absorption.
39
Caloric value (gross energy) of fat per gram is: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Physiological fuel values (Atwater): carbohydrate = 4 kcal/g, protein = 4 kcal/g, fat = 9 kcal/g, alcohol = 7 kcal/g. Fats are the most energy-dense substrate because of their highly reduced state (more H atoms per C).
โœ˜ A wrong: 4 kcal/g is for carbohydrate.
โœ˜ B wrong: 4.1 kcal/g is approximate value for proteins.
โœ˜ C wrong: Not a standard fuel value.
40
Megaloblastic anaemia results from deficiency of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: B12 (cobalamin) and folate are essential for DNA synthesis (methylation cycle, thymidylate synthesis). Deficiency โ†’ impaired DNA synthesis but preserved RNA/protein synthesis โ†’ large immature RBCs (megaloblasts). B12 deficiency adds neurological signs (subacute combined degeneration). Schilling test or methylmalonic acid distinguishes B12 from folate deficiency.
โœ˜ A wrong: Iron deficiency โ†’ microcytic hypochromic anaemia.
โœ˜ B wrong: B6 deficiency โ†’ sideroblastic anaemia.
โœ˜ D wrong: Vitamin C deficiency โ†’ scurvy with normocytic anaemia.
๐Ÿ“Œ High-Yield (Unit II โ€” Print & Memorise)
  1. GIT hormone summary: Gastrin (G-cells, antrum) โ†’ โ†‘ HCl; CCK (I-cells, duodenum) โ†’ gallbladder contraction + pancreatic enzymes; Secretin (S-cells) โ†’ pancreatic HCOโ‚ƒโป; GIP (K-cells) โ†’ โ†‘ insulin; Motilin โ†’ MMC; Ghrelin (stomach) โ†’ hunger.
  2. Intrinsic factor: parietal cells โ†’ binds B12 โ†’ absorbed in terminal ileum. Loss = pernicious anaemia.
  3. BMR โ€” quick numbers: Adult male โ‰ˆ 36 โ€“ 40 kcal/mยฒ/h; female โ‰ˆ 33 โ€“ 37 kcal/mยฒ/h; 1 kcal/kg/h. Increased: hyperthyroidism, fever (+ 13 % per ยฐC), pregnancy. Decreased: hypothyroidism, starvation, sleep, ageing.
  4. Atwater fuel values: CHO 4 ยท Protein 4 ยท Fat 9 ยท Alcohol 7 kcal/g. RQ: CHO 1.0 ยท Protein 0.8 ยท Fat 0.7 ยท Mixed 0.85.
  5. Vitamin deficiency map: A โ†’ night blindness; B1 โ†’ beriberi; B2 โ†’ cheilosis; B3 โ†’ pellagra (3 D's); B6 โ†’ neuropathy; B12/Folate โ†’ megaloblastic anaemia; C โ†’ scurvy; D โ†’ rickets/osteomalacia; E โ†’ haemolytic anaemia; K โ†’ bleeding.
UNIT III
Endocrine System โ€” Glands ยท Hormones ยท Disorders (Q41 โ€“ Q60)
41
The "master gland" of the endocrine system is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: The pituitary, attached to the hypothalamus by the infundibulum and lying in the sella turcica, controls many other endocrine glands via tropic hormones (TSH, ACTH, FSH, LH, GH, PRL from anterior lobe; ADH, oxytocin from posterior lobe). Hence its traditional name "master gland". (Modern view: hypothalamus is the supreme regulator.)
โœ˜ A wrong: Thyroid is regulated by pituitary TSH.
โœ˜ C wrong: Hypothalamus is the supreme controller, but classically the pituitary is termed master gland.
โœ˜ D wrong: Adrenal cortex is regulated by pituitary ACTH.
42
Which hormone is secreted by the posterior pituitary (neurohypophysis)? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: ADH (vasopressin, V2 receptor on collecting ducts) and oxytocin are synthesised in supraoptic and paraventricular nuclei of the hypothalamus, transported via axons, and stored/released from the posterior pituitary. ADH increases water reabsorption (aquaporin-2 insertion). Deficiency โ†’ diabetes insipidus.
โœ˜ B wrong: ACTH is from anterior pituitary corticotrophs.
โœ˜ C wrong: TSH is from anterior pituitary thyrotrophs.
โœ˜ D wrong: GH is from anterior pituitary somatotrophs.
43
Excess growth hormone after closure of epiphyseal plates causes: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Excess GH after epiphyseal closure (adults) โ†’ acromegaly: enlargement of hands, feet, jaw (prognathism), coarse facial features, soft-tissue thickening, organomegaly, glucose intolerance, hypertension. Cause: somatotroph adenoma. Treatment: trans-sphenoidal surgery, somatostatin analogues (octreotide), GH receptor antagonist (pegvisomant).
โœ˜ A wrong: Gigantism is excess GH BEFORE epiphyseal closure (children).
โœ˜ B wrong: Cushing's = excess cortisol.
โœ˜ D wrong: Cretinism = congenital hypothyroidism.
44
The thyroid hormone responsible for most biological effects at the cellular level is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: T4 is secreted in greater quantity (~ 90 %) but T3 is 4 โ€“ 5 ร— more potent and binds nuclear receptors. ~ 80 % of circulating T3 comes from peripheral 5'-deiodination of T4 (catalysed by deiodinases). T3 acts at TRฮฑ/ฮฒ nuclear receptors โ†’ โ†‘ Naโบ/Kโบ ATPase, โ†‘ basal metabolic rate, โ†‘ ฮฒ-adrenergic sensitivity.
โœ˜ A wrong: T4 is a prohormone; less potent.
โœ˜ B wrong: rT3 is biologically inactive.
โœ˜ C wrong: Calcitonin from C-cells regulates Caยฒโบ.
45
Graves' disease is associated with: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Graves' disease is autoimmune hyperthyroidism caused by TSH-receptor stimulating antibodies (TSI / TRAb). Triad: hyperthyroidism + diffuse goitre + ophthalmopathy (exophthalmos) ยฑ pretibial myxoedema. Treatment: methimazole/PTU, radioactive iodine, surgery, ฮฒ-blockers.
โœ˜ B wrong: Anti-TPO antibodies cause Hashimoto's thyroiditis (hypothyroidism).
โœ˜ C wrong: Iodine deficiency causes endemic goitre/hypothyroidism.
โœ˜ D wrong: TSHoma is rare; would show โ†‘ TSH and โ†‘ T4/T3.
46
Parathyroid hormone (PTH) primarily acts to: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: PTH (84 aa) raises serum Caยฒโบ via three actions: (1) โ†‘ bone resorption (osteoclastic activity via RANKL); (2) โ†‘ renal Caยฒโบ reabsorption (DCT) and โ†“ phosphate reabsorption (PCT); (3) โ†‘ renal 1ฮฑ-hydroxylase โ†’ โ†‘ calcitriol โ†’ โ†‘ intestinal Caยฒโบ absorption. Net: โ†‘ Caยฒโบ, โ†“ POโ‚„ยณโป.
โœ˜ A wrong: Calcitonin lowers Caยฒโบ; PTH raises it.
โœ˜ C wrong: Opposite of PTH effect.
โœ˜ D wrong: PTH lowers serum phosphate.
47
Which adrenal cortex zone secretes mineralocorticoid (aldosterone)? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Adrenal cortex layers (mnemonic GFR โ†’ "salt, sugar, sex"): Zona Glomerulosa โ†’ mineralocorticoids (aldosterone โ€” Naโบ retention); Zona Fasciculata โ†’ glucocorticoids (cortisol); Zona Reticularis โ†’ androgens (DHEA). Adrenal medulla โ†’ catecholamines (adrenaline, noradrenaline).
โœ˜ A wrong: Zona reticularis โ†’ androgens.
โœ˜ B wrong: Zona fasciculata โ†’ cortisol.
โœ˜ D wrong: Medulla โ†’ catecholamines.
48
Cushing's syndrome is characterised by all EXCEPT: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Hyperpigmentation occurs only in ACTH-dependent Cushing's (Cushing's disease โ€” pituitary, or ectopic ACTH) due to MSH activity from POMC cleavage. In adrenal-tumour-driven Cushing's, ACTH is suppressed โ†’ no hyperpigmentation. Other features (A, B, C) are common to all causes.
โœ˜ A wrong: Classic Cushingoid habitus.
โœ˜ B wrong: Cortisol โ†’ โ†‘ BP, โ†‘ glucose.
โœ˜ C wrong: Skin atrophy from cortisol.
49
Insulin is secreted by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: ฮฒ-cells (~ 60 โ€“ 70 % of islet) secrete insulin and amylin. ฮฑ-cells (~ 20 %) secrete glucagon. ฮด-cells (~ 5 %) secrete somatostatin. PP / F cells secrete pancreatic polypeptide. Glucose enters ฮฒ-cells via GLUT-2 โ†’ metabolised โ†’ โ†‘ ATP โ†’ closes K_ATP channels โ†’ depolarisation โ†’ Caยฒโบ influx โ†’ insulin exocytosis. Sulfonylureas mimic this by closing K_ATP channels.
โœ˜ A wrong: ฮฑ-cells โ†’ glucagon.
โœ˜ C wrong: ฮด-cells โ†’ somatostatin.
โœ˜ D wrong: PP cells โ†’ pancreatic polypeptide.
50
Type 1 diabetes mellitus is characterised by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Type 1 DM (formerly IDDM, juvenile-onset) is caused by autoimmune destruction of ฮฒ-cells (T-cell mediated, anti-GAD/IA-2/insulin antibodies) โ†’ absolute insulin deficiency โ†’ ketosis-prone. HLA-DR3/DR4 association. Requires lifelong insulin therapy. Type 2 DM is the insulin-resistance disorder (option B).
โœ˜ B wrong: That describes Type 2 DM.
โœ˜ C wrong: ฮฑ-cell hyperplasia is rare; not Type 1.
โœ˜ D wrong: Glucagonoma is glucagon-secreting tumour, not Type 1 DM.
51
Adrenaline (epinephrine) is secreted by the: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Chromaffin cells of the adrenal medulla (modified post-ganglionic sympathetic neurons) secrete catecholamines: adrenaline (~ 80 %) + noradrenaline (~ 20 %). The enzyme PNMT (phenylethanolamine-N-methyltransferase) converts noradrenaline โ†’ adrenaline; PNMT is induced by glucocorticoids from the cortex.
โœ˜ A wrong: Zona glomerulosa โ†’ aldosterone.
โœ˜ B wrong: Zona fasciculata โ†’ cortisol.
โœ˜ D wrong: Pituitary secretes peptide hormones, not catecholamines.
52
Addison's disease is due to: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Addison's disease (primary chronic adrenal insufficiency) is most often autoimmune (90 % in developed countries), occasionally TB or fungal. Loss of cortisol + aldosterone โ†’ hyperpigmentation (high ACTH/MSH), hypotension, hyponatraemia, hyperkalaemia, weakness, hypoglycaemia. Treatment: hydrocortisone + fludrocortisone replacement.
โœ˜ A wrong: Pituitary failure โ†’ secondary adrenal insufficiency (no hyperpigmentation).
โœ˜ B wrong: Conn's syndrome = primary hyperaldosteronism (opposite features).
โœ˜ C wrong: Pheochromocytoma is medullary; causes hypertension.
53
The principal hormone produced by the pineal gland is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Pineal gland (epiphysis cerebri) produces melatonin (N-acetyl-5-methoxytryptamine) from tryptophan via serotonin. Secretion is controlled by light: peaks at night (2 โ€“ 4 am), suppressed by light through retinohypothalamic tract โ†’ SCN โ†’ pineal. Functions: regulation of circadian rhythm, sleep-wake cycle, pubertal timing.
โœ˜ B wrong: Serotonin is precursor of melatonin, not main pineal hormone.
โœ˜ C wrong: Histamine is from mast cells/ECL cells.
โœ˜ D wrong: Dopamine is mainly from substantia nigra/VTA, hypothalamus.
54
Diabetes insipidus is caused by deficiency of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: ADH deficiency (central DI โ€” hypothalamic/pituitary) or unresponsiveness of V2 receptors (nephrogenic DI) โ†’ inability to concentrate urine โ†’ polyuria (> 3 L/day) of dilute urine, polydipsia. Treatment: desmopressin (DDAVP) for central DI; thiazides + amiloride for nephrogenic DI. Differentiate from diabetes mellitus (sweet "honey" urine).
โœ˜ A wrong: Insulin deficiency โ†’ diabetes mellitus.
โœ˜ C wrong: Aldosterone deficiency โ†’ Addison's.
โœ˜ D wrong: Cortisol deficiency โ†’ Addison's.
55
The hormone responsible for milk ejection (let-down reflex) is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Oxytocin (synthesised in PVN of hypothalamus, stored in posterior pituitary) contracts myoepithelial cells of mammary alveoli โ†’ milk ejection (let-down reflex). It also contracts uterine smooth muscle (labour). Suckling-induced neural reflex โ†’ oxytocin release. Prolactin (option A) is responsible for milk synthesis, not ejection.
โœ˜ A wrong: Prolactin โ†’ milk synthesis (lactogenesis).
โœ˜ B wrong: Oestrogen develops ductal system.
โœ˜ D wrong: Progesterone develops alveolar system.
56
Calcitonin secreted by parafollicular C-cells of the thyroid: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Calcitonin (32 aa peptide from C-cells) opposes PTH: it inhibits osteoclast bone resorption and โ†‘ renal Caยฒโบ/POโ‚„ยณโป excretion โ†’ lowers serum Caยฒโบ. It is used therapeutically in osteoporosis, Paget's disease, and hypercalcaemia of malignancy. Salmon calcitonin is most potent. Tumour marker for medullary carcinoma of thyroid.
โœ˜ B wrong: That is PTH action.
โœ˜ C wrong: That is calcitriol action.
โœ˜ D wrong: Calcitonin does affect Caยฒโบ homeostasis.
57
Which of the following hormones acts via cyclic AMP (cAMP) second messenger? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Glucagon binds Gฮฑs-coupled receptor โ†’ activates adenylate cyclase โ†’ โ†‘ cAMP โ†’ activates PKA โ†’ phosphorylates targets (e.g., glycogen phosphorylase). cAMP-using hormones: glucagon, ACTH, TSH, FSH, LH, PTH, ADH (V2), CRH, hCG, calcitonin, ฮฒ-adrenergic. Insulin uses tyrosine kinase; T3/T4 and steroids use nuclear receptors.
โœ˜ A wrong: Insulin โ†’ tyrosine kinase receptor.
โœ˜ B wrong: T3 โ†’ nuclear receptor (TR).
โœ˜ C wrong: Aldosterone โ†’ cytoplasmic mineralocorticoid receptor.
58
Which of the following is NOT a thyroid function test? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: CRP (C-reactive protein) is a non-specific acute-phase inflammatory marker, not a thyroid test. Standard TFTs include TSH (most sensitive screening), Free T4 / T3, Anti-TPO antibodies (Hashimoto's, Graves'), TRAb (Graves'), thyroglobulin (post-thyroidectomy follow-up of differentiated thyroid CA).
โœ˜ A wrong: TSH is the primary screening TFT.
โœ˜ C wrong: Free T4 / T3 are direct measures.
โœ˜ D wrong: Anti-TPO indicates autoimmune thyroiditis.
59
Pheochromocytoma classically presents with: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Pheochromocytoma โ€” a catecholamine-secreting tumour of adrenal medullary chromaffin cells (or extra-adrenal paraganglioma) โ€” follows the "10 % rule": 10 % bilateral, 10 % extra-adrenal, 10 % malignant, 10 % familial, 10 % paediatric. Classic 5 P's: Pressure (BP), Pain (head), Perspiration, Palpitations, Pallor. Diagnosis: 24-h urine metanephrines/VMA. Pre-op: ฮฑ-blockade (phenoxybenzamine) before ฮฒ-blockade.
โœ˜ A wrong: Catecholamines cause hyperglycaemia & weight loss.
โœ˜ B wrong: That is Addisonian electrolyte pattern.
โœ˜ D wrong: Catecholamines cause tachycardia.
60
Which of the following hormones is a peptide? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Insulin is a 51-aa peptide hormone (A-chain 21 aa, B-chain 30 aa linked by 2 disulfide bonds) synthesised as preproinsulin โ†’ proinsulin โ†’ insulin + C-peptide. Other peptides: GH, ACTH, TSH, FSH, LH, PRL, ADH, oxytocin, glucagon, PTH, calcitonin. Steroids: cortisol, aldosterone, sex steroids. Amino-acid derivatives: thyroid hormones, catecholamines.
โœ˜ B wrong: Cortisol is a steroid (from cholesterol).
โœ˜ C wrong: Thyroxine is a tyrosine derivative (iodothyronine).
โœ˜ D wrong: Aldosterone is a mineralocorticoid steroid.
๐Ÿ“Œ High-Yield (Unit III โ€” Print & Memorise)
  1. Pituitary hormones map: Anterior โ€” GH, PRL, ACTH, TSH, FSH, LH (mnemonic "Go Look For The Adenoma Please"); Posterior โ€” ADH, Oxytocin (stored, not synthesised).
  2. Adrenal cortex layers (GFR / "salt, sugar, sex"): G โ€” aldosterone; F โ€” cortisol; R โ€” DHEA. Medulla โ€” adrenaline (~ 80 %) + NA (~ 20 %).
  3. Calcium triad: PTH โ†‘ Caยฒโบ โ†“ POโ‚„ยณโป; Calcitriol โ†‘ Caยฒโบ โ†‘ POโ‚„ยณโป; Calcitonin โ†“ Caยฒโบ. Hypocalcaemia โ†’ Chvostek/Trousseau signs.
  4. Diabetes types: Type 1 โ€” autoimmune ฮฒ-cell destruction, ketosis-prone, anti-GAD; Type 2 โ€” insulin resistance, obese, no ketosis usually; Gestational โ€” pregnancy; MODY โ€” genetic. Diagnostic: FBS โ‰ฅ 126, RBS โ‰ฅ 200 + symptoms, OGTT 2-h โ‰ฅ 200, HbA1c โ‰ฅ 6.5 %.
  5. Endocrine disorder pearls: Acromegaly = adult โ†‘ GH; Gigantism = child โ†‘ GH; Cushing's = โ†‘ cortisol; Addison's = โ†“ cortisol; Conn's = โ†‘ aldosterone; Pheochromocytoma = โ†‘ catecholamines; Graves = autoimmune hyperthyroid; Hashimoto's = autoimmune hypothyroid; DI = โ†“ ADH; SIADH = โ†‘ ADH.
UNIT IV
Reproductive System ยท Pregnancy ยท Lactation ยท Contraception (Q61 โ€“ Q80)
61
Spermatogenesis takes place in: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Spermatogenesis (~ 64 โ€“ 74 days) occurs in the seminiferous tubules: spermatogonia โ†’ primary spermatocytes (meiosis I) โ†’ secondary spermatocytes (meiosis II) โ†’ spermatids โ†’ spermatozoa. Sertoli cells nourish germ cells (blood-testis barrier); Leydig cells (interstitium) secrete testosterone. Maturation/storage continues in the epididymis.
โœ˜ A wrong: Epididymis is for sperm maturation/storage only.
โœ˜ C wrong: Vas deferens transports sperm.
โœ˜ D wrong: Prostate adds seminal fluid.
62
Testosterone is secreted by which cells of the testis? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Leydig (interstitial) cells respond to LH โ†’ secrete testosterone (~ 7 mg/day). Testosterone is converted peripherally to DHT (5ฮฑ-reductase โ€” prostate, skin) and oestradiol (aromatase โ€” fat, brain). Sertoli cells (under FSH) support spermatogenesis, secrete inhibin, ABP and AMH. Negative feedback: testosterone on hypothalamus/pituitary, inhibin on FSH.
โœ˜ B wrong: Sertoli cells nurse germ cells; do not secrete testosterone.
โœ˜ C wrong: Spermatogonia are stem germ cells.
โœ˜ D wrong: Spermatocytes are intermediate germ cells.
63
The phase of the menstrual cycle dominated by oestrogen and characterised by Graafian follicle development is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Follicular phase (Days 1 โ€“ 14): FSH stimulates follicular growth โ†’ dominant follicle (Graafian) โ†’ โ†‘ oestradiol โ†’ endometrial proliferation. Mid-cycle oestrogen surge triggers LH surge โ†’ ovulation (Day 14). Luteal phase (Days 14 โ€“ 28): corpus luteum secretes progesterone โ†’ secretory endometrium. Cycle is 28 ยฑ 7 days.
โœ˜ A wrong: Menstrual phase = sloughing of endometrium.
โœ˜ B wrong: Luteal phase is progesterone-dominant.
โœ˜ D wrong: Ischaemic phase is end of luteal (just before menses).
64
Ovulation is triggered by a surge of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: A 24 โ€“ 36 h LH surge (mid-cycle, ~ Day 13) triggers ovulation (Day 14). The trigger is positive feedback by sustained high oestradiol on the hypothalamus/pituitary. The surge โ†’ completion of meiosis I in oocyte โ†’ release of secondary oocyte (arrested at metaphase II) โ†’ corpus luteum formation. Home ovulation kits detect this LH surge.
โœ˜ A wrong: FSH stimulates follicular growth, not ovulation.
โœ˜ B wrong: Oestrogen rise triggers LH surge but is not itself the trigger.
โœ˜ C wrong: Progesterone rises after ovulation.
65
The corpus luteum primarily secretes: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: The corpus luteum (yellow body) is the post-ovulatory remnant of the Graafian follicle. It secretes progesterone (predominantly) and oestrogen, maintaining the secretory endometrium. If pregnancy occurs, hCG (from trophoblast) maintains the corpus luteum until placenta takes over (~ 10 weeks). Without pregnancy, the corpus luteum regresses โ†’ corpus albicans โ†’ menstruation.
โœ˜ B wrong: FSH is from anterior pituitary.
โœ˜ C wrong: LH is from anterior pituitary.
โœ˜ D wrong: Inhibin is a minor product, not the principal hormone.
66
Fertilization normally takes place in the: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Fertilisation occurs in the ampulla โ€” the widest, longest part of the fallopian (uterine) tube. The zygote then divides as it travels (~ 5 days) to reach the uterine cavity for implantation (~ Day 7). Tubal motility, ciliary action and capacitated sperm are essential for fertilisation. Disorders of tubal patency cause infertility/ectopic pregnancy.
โœ˜ A wrong: Uterus is implantation site, not fertilisation.
โœ˜ C wrong: Cervix is sperm reservoir.
โœ˜ D wrong: Sperm deposited in vagina; do not fertilise there.
67
Implantation of the blastocyst into the endometrium occurs approximately on day: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Embryonic timeline: Day 0 fertilisation โ†’ Day 3 morula (16-cell) โ†’ Day 4-5 blastocyst โ†’ Day 6 hatching โ†’ Day 6 โ€“ 7 implantation (apposition then invasion). Trophoblast cells invade endometrium, forming syncytiotrophoblast which secretes hCG (detectable in maternal serum from ~ Day 8).
โœ˜ A wrong: Day 1 โ€“ 2: cleavage stage; still in tube.
โœ˜ B wrong: Day 3 โ€“ 4: morula; blastocyst not yet formed.
โœ˜ D wrong: Day 14 โ€“ 15 is gastrulation (post-implantation).
68
Human chorionic gonadotropin (hCG) is secreted by the: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: hCG is a glycoprotein (ฮฑ-subunit similar to LH/FSH/TSH; ฮฒ-subunit unique) secreted by the syncytiotrophoblast from ~ Day 8 of pregnancy. It maintains the corpus luteum (luteotropic) โ†’ continues progesterone secretion to maintain pregnancy until placenta takes over (~ 10 wk). hCG peaks at ~ 10 wk then declines. Basis of pregnancy tests (urine/serum ฮฒ-hCG).
โœ˜ A wrong: Pituitary secretes LH/FSH; hCG is structurally similar but placental.
โœ˜ B wrong: Corpus luteum is the target of hCG, not its source.
โœ˜ C wrong: Hypothalamus secretes GnRH, not hCG.
69
Normal duration of human pregnancy from LMP is: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Pregnancy = 280 days = 40 weeks = 9 calendar months from LMP (last menstrual period). Naegele's rule: EDD = LMP + 7 days โˆ’ 3 months + 1 year. Trimesters: 1st (1 โ€“ 13 wk), 2nd (14 โ€“ 26 wk), 3rd (27 โ€“ 40 wk). Term: 37 โ€“ 42 wk. Pre-term: < 37 wk. Post-term: > 42 wk.
โœ˜ B wrong: 36 weeks is preterm.
โœ˜ C wrong: 30 weeks is markedly preterm.
โœ˜ D wrong: 50 weeks exceeds normal.
70
Which hormone is responsible for milk synthesis (lactogenesis)? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Prolactin from anterior pituitary lactotrophs initiates and maintains milk synthesis. During pregnancy, oestrogen โ†‘ prolactin (milk synthesis blocked because of high E + P); after parturition, โ†“ E/P unmasks prolactin's effect โ†’ lactogenesis. Suckling stimulates further prolactin (synthesis) and oxytocin (ejection). Dopamine inhibits prolactin (PIH).
โœ˜ A wrong: Oxytocin causes milk EJECTION, not synthesis.
โœ˜ C wrong: Oestrogen develops ductal system but inhibits lactation in pregnancy.
โœ˜ D wrong: FSH has no role in lactation.
71
Combined oral contraceptive pills (COCs) primarily prevent pregnancy by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: COCs (ethinyloestradiol + progestin, e.g., levonorgestrel) suppress GnRH/FSH/LH โ†’ no follicular development, no LH surge โ†’ no ovulation. They also thicken cervical mucus, alter endometrium (less receptive) and reduce tubal motility. Pearl Index โ‰ˆ 0.3 (perfect use) โ€“ 9 (typical). Side-effects: VTE risk, breast tenderness, breakthrough bleeding.
โœ˜ A wrong: Spermicides do that, not OCPs.
โœ˜ B wrong: OCPs are not abortifacient.
โœ˜ D wrong: Withdrawal bleed mimics menses but is not their mechanism.
72
Which method has the lowest Pearl Index (most effective)? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Pearl Index (pregnancies per 100 women-years): vasectomy โ‰ˆ 0.1, tubal ligation โ‰ˆ 0.5, IUDs (Cu-T 380A) โ‰ˆ 0.6, COC โ‰ˆ 0.3 perfect, condom โ‰ˆ 2 โ€“ 18, withdrawal โ‰ˆ 4 โ€“ 22, rhythm method โ‰ˆ 9 โ€“ 25. Lower index = more effective. Sterilisation provides permanent contraception with the lowest failure rate.
โœ˜ B wrong: Condoms have higher typical-use failure.
โœ˜ C wrong: Withdrawal has high failure rate.
โœ˜ D wrong: Rhythm method is least reliable of these.
73
Cu-T (copper IUD) primarily prevents pregnancy by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Cuยฒโบ ions released from copper IUDs are spermicidal/spermostatic and produce a sterile inflammatory endometrial reaction that is hostile to implantation. They also alter cervical mucus and tubal motility. Cu-T 380A is effective for 10 years. They do NOT inhibit ovulation. Hormonal IUDs (Mirenaยฎ/LNG-IUS) use levonorgestrel.
โœ˜ A wrong: Ovulation continues with Cu-IUD.
โœ˜ B wrong: Bleeding is a side effect, not mechanism.
โœ˜ C wrong: Prolactin is unrelated.
74
Emergency contraceptive levonorgestrel must be taken within: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Levonorgestrel (1.5 mg single dose; e.g., I-Pillยฎ / Plan-Bยฎ) is recommended within 72 h of unprotected intercourse โ€” earliest is most effective (95 % within 24 h, ~ 58 % at 49 โ€“ 72 h). Mechanism: delays/prevents ovulation, alters cervical mucus. Ulipristal acetate is effective up to 120 h. Cu-IUD is the most effective EC up to 5 days.
โœ˜ A wrong: 24 h limit is too narrow.
โœ˜ C wrong: 5 days applies to Cu-IUD/ulipristal, not LNG.
โœ˜ D wrong: EC is post-coital, not pre.
75
Vasectomy involves: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Vasectomy is bilateral cutting/ligating of the vas deferens (out-patient, local anaesthesia) โ†’ sperm cannot reach the urethra. Hormonal function (testosterone) is preserved. Ejaculate volume is unchanged but azoospermic (after ~ 2 โ€“ 3 months / 20 ejaculations โ€” confirmed by post-vasectomy semen analysis). Considered permanent though microsurgical reversal possible.
โœ˜ B wrong: Orchidectomy = removal of testis.
โœ˜ C wrong: Seminiferous tubules are not cut in vasectomy.
โœ˜ D wrong: Prostatectomy is unrelated to contraception.
76
Which structure separates maternal and fetal blood without allowing direct mixing? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: The placental membrane (haemochorial type in humans) separates fetal and maternal blood but allows transfer of Oโ‚‚, COโ‚‚, glucose, amino acids, water, electrolytes, drugs, immunoglobulin G (IgG), some viruses (TORCH). Layers: syncytiotrophoblast โ†’ cytotrophoblast (early) โ†’ mesenchyme โ†’ fetal capillary endothelium. By term, only syncytiotrophoblast + endothelium remain (vasculosyncytial membrane).
โœ˜ A wrong: Endometrium is the maternal lining; it transforms into decidua during pregnancy.
โœ˜ B wrong: Decidua is one component, not the barrier itself.
โœ˜ D wrong: Amnion is fetal membrane, not the placental barrier.
77
During parturition, the hormone that strongly stimulates uterine contraction is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Oxytocin from the posterior pituitary causes uterine smooth muscle contraction by binding G_q-coupled OT-receptors โ†’ โ†‘ IPโ‚ƒ โ†’ โ†‘ Caยฒโบ. The Ferguson reflex amplifies labour: cervical stretch โ†’ โ†‘ oxytocin. Synthetic oxytocin (Pitocinยฎ) is used to induce/augment labour and to prevent post-partum haemorrhage. Prostaglandins (PGF2ฮฑ, PGE2) cooperate.
โœ˜ B wrong: Progesterone has uterine-relaxant ("pro-gestation") effect; declines before labour.
โœ˜ C wrong: Insulin has no obstetric role.
โœ˜ D wrong: FSH is unrelated to parturition.
78
Colostrum, secreted in the first 2 โ€“ 4 days after parturition, is rich in: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Colostrum (yellow, viscous) is rich in immunoglobulins (especially secretory IgA), lactoferrin, lysozyme, white blood cells, vitamin A and protein, but lower in fat and lactose than mature milk. Provides passive immunity (mucosal protection), gut microbiome priming and a laxative effect. Volume small (~ 30 โ€“ 100 mL/day) but highly nutritious for the newborn.
โœ˜ A wrong: Lactose is higher in mature milk.
โœ˜ B wrong: Triglycerides increase later in mature milk.
โœ˜ C wrong: Iron content is low; casein concentration is lower than mature milk.
79
Menopause is defined as: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Menopause = cessation of menses for โ‰ฅ 12 consecutive months due to ovarian follicular depletion (mean age ~ 51 yr). Hormonal: โ†“โ†“ oestrogen, โ†‘โ†‘ FSH (> 30 IU/L), โ†‘ LH. Symptoms: hot flushes, night sweats, vaginal dryness, mood changes, osteoporosis, โ†‘ CV risk. Premature menopause < 40 yr (POI). Hormone replacement therapy (HRT) for symptoms in selected cases.
โœ˜ A wrong: Anovulation occurs; menopause is the menstrual end-point.
โœ˜ C wrong: First menses = menarche.
โœ˜ D wrong: Painful periods = dysmenorrhoea.
80
Which of the following is a barrier method of contraception? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Barrier methods physically prevent sperm meeting ovum. Examples: male/female condoms, diaphragm, cervical cap (often with spermicide). They also offer some protection against STIs. OCPs are hormonal, IUDs are intrauterine devices, vasectomy is sterilisation. Pearl Index of barrier methods is moderate (typical use 12 โ€“ 18 / 100 women-yrs).
โœ˜ A wrong: OCP = hormonal.
โœ˜ B wrong: Cu-T = intrauterine device.
โœ˜ D wrong: Vasectomy = sterilisation.
๐Ÿ“Œ High-Yield (Unit IV โ€” Print & Memorise)
  1. Menstrual cycle: Day 1 โ€“ 5 menses; Day 1 โ€“ 14 follicular (oestrogen-dominant); Day 14 ovulation (LH surge); Day 14 โ€“ 28 luteal (progesterone-dominant). Body temp โ†‘ 0.3 โ€“ 0.5 ยฐC after ovulation.
  2. HPG axis: Hypothalamus GnRH (pulsatile) โ†’ Pituitary FSH/LH โ†’ Gonads (T/E2/P). Negative feedback by sex steroids; positive feedback by oestradiol triggers LH surge.
  3. Pregnancy timeline: Fertilisation Day 0 (ampulla) โ†’ blastocyst Day 5 โ†’ implantation Day 6 โ€“ 7 โ†’ hCG detectable Day 8 โ†’ fetal heartbeat 5 โ€“ 6 wk โ†’ quickening 18 โ€“ 20 wk โ†’ term 37 โ€“ 42 wk.
  4. Lactation hormones: Prolactin = milk synthesis; Oxytocin = milk ejection (let-down); during pregnancy โ†‘ E + P inhibit milk; post-delivery โ†“ E/P unmasks prolactin โ†’ lactogenesis. Suckling = neuro-endocrine reflex.
  5. Contraception ladder (most โ†’ least effective): Sterilisation (PI < 0.5) โ†’ IUD (PI 0.6 โ€“ 0.8) โ†’ COC (PI 0.3 โ€“ 9) โ†’ Injectable/Implant โ†’ Condom โ†’ Withdrawal/Rhythm. Emergency: LNG โ‰ค 72 h, ulipristal โ‰ค 120 h, Cu-IUD โ‰ค 5 d.
UNIT V
Renal ยท Body Fluids ยท Immunity ยท Skin (Q81 โ€“ Q100)
81
The functional unit of the kidney is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Each kidney has ~ 1 million nephrons. A nephron consists of renal corpuscle (Bowman's capsule + glomerulus) + renal tubule (PCT, Loop of Henle, DCT, collecting duct). Two types: cortical (~ 85 %, short loops) and juxtamedullary (~ 15 %, long loops in medulla โ€” concentrate urine).
โœ˜ A wrong: Glomerulus is part of the nephron, not the entire unit.
โœ˜ C wrong: Renal corpuscle is one component of nephron.
โœ˜ D wrong: Renal tubule is one component.
82
Normal glomerular filtration rate (GFR) in healthy adults is approximately: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Normal GFR is ~ 125 mL/min (180 L/day). Of this, > 99 % is reabsorbed; only ~ 1 โ€“ 1.5 L is excreted as urine. Renal blood flow โ‰ˆ 1.2 L/min (~ 25 % of cardiac output). GFR is measured by creatinine or inulin clearance. CKD staging: Stage 1 โ‰ฅ 90, Stage 5 < 15 mL/min/1.73 mยฒ.
โœ˜ B wrong: 50 mL/min indicates renal impairment.
โœ˜ C wrong: 250 mL/min is too high.
โœ˜ D wrong: 1000 mL/min approximates renal blood flow, not GFR.
83
The juxtaglomerular apparatus secretes: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: JG cells (modified smooth muscle of afferent arteriole) secrete renin in response to โ†“ BP, โ†“ NaCl at macula densa, or ฮฒ1-sympathetic stimulation. Renin cleaves angiotensinogen โ†’ AT-I โ†’ (ACE) โ†’ AT-II โ†’ vasoconstriction + aldosterone release โ†’ Na/Hโ‚‚O retention โ†’ โ†‘ BP. RAAS is the body's primary BP-regulatory system.
โœ˜ A wrong: Aldosterone is from adrenal cortex (zona glomerulosa).
โœ˜ B wrong: Erythropoietin is from peritubular interstitial cells, not JG.
โœ˜ D wrong: ANP is from cardiac atria.
84
Most filtered glucose is reabsorbed in the: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: ~ 90 % of filtered glucose is reabsorbed by SGLT-2 in early PCT (low affinity, high capacity), the rest by SGLT-1 in late PCT (high affinity, low capacity). Renal threshold for glucose ~ 180 mg/dL. SGLT-2 inhibitors (e.g., empagliflozin, dapagliflozin) are antidiabetic drugs that cause glucosuria โ†’ โ†“ HbA1c, weight, BP, CV mortality.
โœ˜ A wrong: DCT reabsorbs Na/Cl/Ca.
โœ˜ B wrong: Loop reabsorbs Na/K/2Cl + water (descending).
โœ˜ C wrong: Collecting duct fine-tunes Na/K/Hโ‚‚O.
85
Aldosterone acts on the kidney to: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Aldosterone (mineralocorticoid) binds nuclear MR โ†’ โ†‘ ENaC and Na/K ATPase in principal cells of late DCT/CD โ†’ Naโบ retention (water follows osmotically), Kโบ and Hโบ secretion. Net: โ†‘ ECF volume, โ†‘ BP, hypokalaemia, alkalosis. Spironolactone/eplerenone block MR; amiloride blocks ENaC.
โœ˜ B wrong: Glucose reabsorption is via SGLT-2, not aldosterone.
โœ˜ C wrong: Aldosterone increases BP.
โœ˜ D wrong: Aldosterone does not regulate ADH directly.
86
Antidiuretic hormone (ADH) increases water reabsorption by: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: ADH binds V2 receptors on principal cells of collecting duct โ†’ Gฮฑs โ†’ โ†‘ cAMP โ†’ PKA โ†’ translocation of pre-formed AQP-2 to apical membrane โ†’ water reabsorption (down osmotic gradient created by medullary hypertonicity). V1 receptors (vascular smooth muscle) cause vasoconstriction. Disorders: SIADH (โ†‘ ADH โ†’ dilutional hyponatraemia), DI (โ†“ ADH โ†’ polyuria).
โœ˜ A wrong: Naโบ channel insertion is by aldosterone.
โœ˜ C wrong: ADH does not act primarily on GFR.
โœ˜ D wrong: NKCCโ‚‚ is in thick ascending limb (loop diuretics).
87
Total body water (TBW) constitutes about __ % of body weight in adult males: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Adult male TBW โ‰ˆ 60 % body weight (female โ‰ˆ 50 % โ€” more adipose tissue). Distribution: ICF โ‰ˆ 40 % (โ…” of TBW), ECF โ‰ˆ 20 % (โ…“ of TBW). ECF subdivides into interstitial (~ 15 %) and plasma (~ 5 %). 60-40-20 rule. Newborns ~ 75 %, elderly lower.
โœ˜ B wrong: 30 % approximates ICF only.
โœ˜ C wrong: Too high for adult.
โœ˜ D wrong: Approximates ECF only.
88
The normal pH range of arterial blood is: Most Probable

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Arterial pH = 7.35 โ€“ 7.45 (mean 7.4). pH < 7.35 = acidaemia; > 7.45 = alkalaemia. Maintained by buffers (HCOโ‚ƒโป/Hโ‚‚COโ‚ƒ โ€” Henderson-Hasselbalch), respiratory regulation (COโ‚‚), and renal regulation (HCOโ‚ƒโป reabsorption + Hโบ secretion). Major disorders: respiratory/metabolic acidosis or alkalosis. ABG provides pH, PCOโ‚‚, POโ‚‚, HCOโ‚ƒโป.
โœ˜ A wrong: Severe acidosis; not normal.
โœ˜ B wrong: Acidosis, not normal.
โœ˜ D wrong: Alkalosis, not normal.
89
The principal extracellular cation is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Naโบ is the major ECF cation (~ 140 mEq/L); Clโป is the major ECF anion (~ 100 mEq/L). Kโบ is the major ICF cation (~ 150 mEq/L); proteins/HPOโ‚„ยฒโป are major ICF anions. Na/K ATPase (3 Naโบ out, 2 Kโบ in) maintains gradients. Hyponatraemia < 135 mEq/L (commonest electrolyte disorder); hypernatraemia > 145.
โœ˜ A wrong: Kโบ is intracellular.
โœ˜ B wrong: Mgยฒโบ is mainly intracellular.
โœ˜ C wrong: Caยฒโบ is mainly stored intracellularly/in bone.
90
The principal buffer in extracellular fluid is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: The HCOโ‚ƒโป/Hโ‚‚COโ‚ƒ system is the most important ECF buffer because it is open: lungs blow off COโ‚‚; kidneys reclaim HCOโ‚ƒโป. Henderson-Hasselbalch: pH = 6.1 + log [HCOโ‚ƒโป]/(0.03 ร— PCOโ‚‚). Other buffers: phosphate (intracellular and urine), proteins (especially intracellular), and haemoglobin (RBC).
โœ˜ A wrong: Phosphate is more intracellular and urinary.
โœ˜ B wrong: Protein buffers are mainly intracellular.
โœ˜ D wrong: Hb is RBC-specific.
91
B-lymphocytes mature in: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: B-cells (humoral immunity) develop and mature in bone marrow โ†’ migrate to secondary lymphoid organs (spleen, lymph nodes, MALT) where antigen activation occurs. Activated B-cells differentiate into plasma cells (antibody-secreting) and memory B-cells. T-cells originate in bone marrow but mature in the thymus (positive/negative selection).
โœ˜ A wrong: Thymus is for T-cell maturation.
โœ˜ C wrong: Lymph nodes are sites of antigen-driven activation, not maturation.
โœ˜ D wrong: Spleen is secondary lymphoid organ.
92
The most abundant immunoglobulin in human serum is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: IgG accounts for ~ 75 % of serum immunoglobulin. Functions: opsonisation, complement activation, neutralisation, ADCC. Only Ig that crosses the placenta โ†’ passive immunity to fetus. IgA dimer (10 โ€“ 15 %, secretory mucosal); IgM pentamer (10 %, primary response); IgD (membrane B-cell receptor); IgE (< 1 %, allergy/anti-helminth).
โœ˜ B wrong: IgA is second-most abundant; predominant in secretions.
โœ˜ C wrong: IgM is the largest pentamer; primary response.
โœ˜ D wrong: IgE is least abundant.
93
Which immunoglobulin crosses the placenta to provide passive immunity to the fetus? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Only IgG crosses the placenta (active transport via FcRn receptor). It provides passive humoral immunity to the fetus (lasts ~ 6 months postnatal). Newborns therefore start producing their own IgM (first), then IgG. Elevated cord-blood IgM suggests congenital infection (TORCH). Secretory IgA in colostrum/breast milk provides additional mucosal immunity.
โœ˜ A wrong: IgA passes via breast milk, not placenta.
โœ˜ B wrong: IgM is too large; does not cross placenta.
โœ˜ D wrong: IgE does not cross placenta.
94
In type I hypersensitivity (anaphylaxis), the principal mediator released from mast cells is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Type I (immediate) hypersensitivity: allergen โ†’ IgE binding to FcฮตRI on mast cells โ†’ cross-linking โ†’ degranulation โ†’ release of preformed (histamine, tryptase, heparin) and newly synthesized (PGD2, LTC4/D4/E4, PAF, cytokines) mediators โ†’ vasodilation, โ†‘ vascular permeability, bronchoconstriction. Treatment of anaphylaxis: IM adrenaline 0.5 mg.
โœ˜ A wrong: Bradykinin is a kinin from kallikrein system.
โœ˜ B wrong: ACh is a neurotransmitter, not a mast-cell mediator.
โœ˜ C wrong: Cortisol is anti-inflammatory.
95
Cell-mediated immunity is primarily a function of: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: T-cells (mature in thymus) mediate cellular immunity. CD4โบ T-helper cells (recognise MHC II) coordinate adaptive responses (Th1, Th2, Th17, Treg subsets). CD8โบ cytotoxic T-cells (recognise MHC I) kill virus-infected/tumour cells. NK cells (innate) provide additional cytotoxicity. B-cells/plasma cells mediate humoral (antibody) immunity.
โœ˜ B wrong: B-cells mediate humoral immunity.
โœ˜ C wrong: Plasma cells secrete antibodies.
โœ˜ D wrong: Eosinophils participate in allergy/anti-parasite, not classical CMI.
96
The largest organ of the human body is: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Skin is the largest organ (surface area ~ 1.5 โ€“ 2 mยฒ; ~ 16 % body weight). Three layers: epidermis (stratum basale โ†’ spinosum โ†’ granulosum โ†’ lucidum [palms/soles] โ†’ corneum), dermis (collagen, elastin, vessels, nerves, glands), hypodermis (subcutaneous fat). Functions: barrier, thermoregulation, sensation, vitamin D synthesis, immunity (Langerhans cells), excretion.
โœ˜ A wrong: Liver is the largest INTERNAL organ.
โœ˜ B wrong: Brain is smaller.
โœ˜ D wrong: Lungs are smaller than skin.
97
The pigment responsible for skin colour is: GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” B: Melanin (eumelanin black-brown, pheomelanin red-yellow) is synthesised by melanocytes (stratum basale of epidermis) from tyrosine via tyrosinase. UV radiation stimulates production โ†’ tan. Albinism = tyrosinase deficiency. Melanin protects against UV damage. Carotene (yellow-orange) and haemoglobin (red, dermal blood) contribute secondarily.
โœ˜ A wrong: Bilirubin causes jaundice (yellow), not normal skin colour.
โœ˜ C wrong: Carotene contributes minimally.
โœ˜ D wrong: Hb gives pinkish hue but is not the principal pigment.
98
Active immunity differs from passive immunity in that: Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” A: Active immunity = host's own immune system makes antibodies/cells; long-lasting (months โ€“ lifelong) but slow onset. Examples: natural infection, vaccination. Passive immunity = preformed antibodies transferred (placental IgG, breast-milk IgA, immune globulin/antitoxin); fast onset but short-lived (weeks โ€“ months) and no memory.
โœ˜ B wrong: Active immunity is long-lasting.
โœ˜ C wrong: Transfer of antibodies = passive.
โœ˜ D wrong: Active immunity is for any age.
99
Which gland of the skin is responsible for thermoregulatory sweating? GPAT-Verified

๐Ÿ“˜ Explanation

โœ” Correct โ€” D: Eccrine sweat glands (~ 2 โ€“ 4 million; over entire body, dense in palms/soles/forehead) secrete dilute hypotonic sweat (water + NaCl + urea + lactate) directly onto skin via simple ducts. Innervated by sympathetic CHOLINERGIC fibres. Major thermoregulator (evaporative cooling). Apocrine glands (axilla, perineum) secrete protein-rich fluid acted on by skin bacteria โ†’ body odour. Sebaceous glands secrete sebum.
โœ˜ A wrong: Sebaceous glands secrete sebum (lubrication), not sweat.
โœ˜ B wrong: Apocrine glands act in scent/pheromones, not principal cooling.
โœ˜ C wrong: Ceruminous glands produce earwax.
100
Which of the following cells in the epidermis are antigen-presenting (immune surveillance)? Practice

๐Ÿ“˜ Explanation

โœ” Correct โ€” C: Langerhans cells (dendritic cells of epidermis, mainly in stratum spinosum) are antigen-presenting cells (MHC II positive); they capture cutaneous antigens, migrate to regional lymph nodes, and activate T-cells. Origin: bone marrow. Birbeck granules are characteristic. Cell types of epidermis: Keratinocytes (90 %, barrier), Melanocytes (pigment), Langerhans (immunity), Merkel (touch).
โœ˜ A wrong: Keratinocytes are barrier cells (most numerous).
โœ˜ B wrong: Melanocytes produce pigment.
โœ˜ D wrong: Merkel cells are touch (mechano-) receptors.
๐Ÿ“Œ High-Yield (Unit V โ€” Print & Memorise)
  1. Nephron quick-reference: GFR 125 mL/min ยท Renal blood flow ~ 1.2 L/min ยท Threshold for glucose ~ 180 mg/dL ยท Loop of Henle = countercurrent multiplier ยท ADH acts on V2 (collecting duct) ยท Aldosterone acts on late DCT/CD.
  2. RAAS axis: โ†“ BP / โ†“ NaCl โ†’ JG renin โ†’ AGT โ†’ AT-I โ†’ (ACE) โ†’ AT-II โ†’ vasoconstriction + aldosterone โ†’ Naโบ/Hโ‚‚O retention โ†’ โ†‘ BP. Drugs: ACEI (-pril), ARB (-sartan), aliskiren, MR antagonists.
  3. Body fluid 60-40-20 rule (% body weight): TBW 60 %, ICF 40 %, ECF 20 % (interstitial 15 %, plasma 5 %). Female ~ 50 %. Major ECF cation Naโบ (140), ICF cation Kโบ (150), ECF anion Clโป (100).
  4. Immunoglobulin facts: IgG most abundant + crosses placenta ยท IgM first formed (pentamer, primary response) ยท IgA dimer in secretions ยท IgE allergy/anti-parasite ยท IgD B-cell receptor. Active = own response (long); Passive = preformed Ab (short).
  5. Skin layers (deep โ†’ superficial in epidermis): "Come, Let's Get Sun Burnt" = Corneum, Lucidum, Granulosum, Spinosum, Basale (reverse order superficial โ†’ deep). Cells: Keratinocytes, Melanocytes, Langerhans, Merkel.

๐Ÿ“š Mr. K. Mallikarjuna Reddy, M.Pharm., (Ph.D.)

Assistant Professor ยท Department of Pharmaceutics

SVU College of Pharmaceutical Sciences ยท Sri Venkateswara University, Tirupati โ€“ 517502, A.P., India

๐Ÿ“ง mallikapharm@gmail.com  |  ๐Ÿ“ฑ +91-9000000000

ยฉ 2026 KMR ยท GPAT Question Bank Series ยท Volume 2.1 โ€” Human Anatomy & Physiology II ยท For B.Pharm/D.Pharm/GPAT/NIPER aspirants

๐Ÿ‘จโ€๐Ÿซ Authored & Developed By

Mr. K. Mallikarjuna Reddy

Associate Professor, M. Pharma (Pharmacology)

๐Ÿ›๏ธ Institution

Vasantidevi Patil Institute of Pharmacy

Kodali, Maharashtra, India

๐Ÿ“ฌ Contact & Web

๐Ÿ“ง mallikaphd@gmail.com

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๐Ÿ“š GPAT Question Bank ยท Vasantidevi Patil Institute of Pharmacy ยท Kodali, Maharashtra ยท For PCI B.Pharm Curriculum