1. What is the resting membrane potential of a typical mammalian neuron?
Correct Answer: B (-70 mV)
The resting membrane potential is typically -70 mV, established primarily by high potassium permeability and the electrogenic Na+/K+ ATPase pump.
The resting membrane potential is typically -70 mV, established primarily by high potassium permeability and the electrogenic Na+/K+ ATPase pump.
2. Which ion influx is directly responsible for depolarizing the axonal membrane during an action potential?
Correct Answer: A (Sodium ions (Na⁺))
Depolarization occurs due to the rapid opening of voltage-gated sodium channels, allowing a swift inward flux of Na⁺ down its electrochemical gradient.
Depolarization occurs due to the rapid opening of voltage-gated sodium channels, allowing a swift inward flux of Na⁺ down its electrochemical gradient.
3. Repolarization of an axonal membrane occurs primarily due to:
Correct Answer: B (Outward diffusion of K⁺)
Repolarization results from the closure of voltage-gated Na⁺ channels and the opening of voltage-gated K⁺ channels, causing K⁺ efflux.
Repolarization results from the closure of voltage-gated Na⁺ channels and the opening of voltage-gated K⁺ channels, causing K⁺ efflux.
4. The sodium-potassium pump (Na⁺/K⁺ ATPase) transports:
Correct Answer: B (3 Na⁺ out for 2 K⁺ in)
The electrogenic Na⁺/K⁺ pump hydrolyzes one ATP molecule to actively extrude 3 Na⁺ ions while importing 2 K⁺ ions.
The electrogenic Na⁺/K⁺ pump hydrolyzes one ATP molecule to actively extrude 3 Na⁺ ions while importing 2 K⁺ ions.
5. Myelin sheaths around axons in the Central Nervous System (CNS) are formed by:
Correct Answer: B (Oligodendrocytes)
Oligodendrocytes myelinate multiple axons in the CNS, whereas Schwann cells produce myelin sheaths exclusively in the Peripheral Nervous System (PNS).
Oligodendrocytes myelinate multiple axons in the CNS, whereas Schwann cells produce myelin sheaths exclusively in the Peripheral Nervous System (PNS).
6. Nissl granules found in neuronal cyton and dendrites are composed of:
Correct Answer: B (Rough endoplasmic reticulum and free ribosomes)
Nissl granules are specialized basophilic masses of rough endoplasmic reticulum and polyribosomes dedicated to continuous protein synthesis.
Nissl granules are specialized basophilic masses of rough endoplasmic reticulum and polyribosomes dedicated to continuous protein synthesis.
7. The gaps between adjacent myelin sheaths along an axon are called:
Correct Answer: B (Nodes of Ranvier)
Nodes of Ranvier are unmyelinated regions rich in voltage-gated sodium channels, enabling saltatory conduction of impulses.
Nodes of Ranvier are unmyelinated regions rich in voltage-gated sodium channels, enabling saltatory conduction of impulses.
8. Saltatory conduction is characteristic of:
Correct Answer: B (Myelinated nerve fibers)
In myelinated neurons, the action potential jumps from one node of Ranvier to the next, drastically accelerating transmission speed and conserving energy.
In myelinated neurons, the action potential jumps from one node of Ranvier to the next, drastically accelerating transmission speed and conserving energy.
9. Which ion triggers the exocytosis of neurotransmitter vesicles at the presynaptic terminal?
Correct Answer: C (Calcium (Ca²⁺))
Action potential arrival opens voltage-gated Ca²⁺ channels; the inward Ca²⁺ surge activates synaptotagmin to trigger synaptic vesicle fusion.
Action potential arrival opens voltage-gated Ca²⁺ channels; the inward Ca²⁺ surge activates synaptotagmin to trigger synaptic vesicle fusion.
10. The thick band of transverse commissural nerve fibers connecting the two cerebral hemispheres is the:
Correct Answer: B (Corpus callosum)
The corpus callosum is a prominent C-shaped tract of myelinated nerve fibers connecting the left and right cerebral hemispheres in mammals.
The corpus callosum is a prominent C-shaped tract of myelinated nerve fibers connecting the left and right cerebral hemispheres in mammals.
11. The primary thermoregulatory center of the human body is located in the:
Correct Answer: B (Hypothalamus)
The hypothalamus contains preoptic nuclei that act as the body’s central thermostat, regulating heat loss and heat gain mechanisms.
The hypothalamus contains preoptic nuclei that act as the body’s central thermostat, regulating heat loss and heat gain mechanisms.
12. Corpora quadrigemina are characteristic anatomical structures located in the dorsal region of the:
Correct Answer: B (Midbrain)
The dorsal midbrain (tectum) bears four colliculi (corpora quadrigemina): two superior colliculi for visual reflexes and two inferior for auditory reflexes.
The dorsal midbrain (tectum) bears four colliculi (corpora quadrigemina): two superior colliculi for visual reflexes and two inferior for auditory reflexes.
13. The canal passing through the midbrain connecting the third and fourth ventricles is the:
Correct Answer: B (Cerebral aqueduct (Aqueduct of Sylvius))
The cerebral aqueduct is a narrow conduit within the midbrain that conveys cerebrospinal fluid from the diencephalic third ventricle to the fourth ventricle.
The cerebral aqueduct is a narrow conduit within the midbrain that conveys cerebrospinal fluid from the diencephalic third ventricle to the fourth ventricle.
14. The center for controlling involuntary activities like respiration, cardiovascular reflexes, and gastric secretions is:
Correct Answer: C (Medulla oblongata)
The medulla oblongata houses vital autonomic centers for cardiac rhythm, respiratory drive (dorsal/ventral groups), vasomotor tone, and vomiting reflexes.
The medulla oblongata houses vital autonomic centers for cardiac rhythm, respiratory drive (dorsal/ventral groups), vasomotor tone, and vomiting reflexes.
15. The human brain region responsible for maintaining balance, posture, and coordination of voluntary movements is:
Correct Answer: B (Cerebellum)
The cerebellum integrates sensory inputs from vestibular apparatus and proprioceptors to fine-tune and coordinate skeletal muscle contractions.
The cerebellum integrates sensory inputs from vestibular apparatus and proprioceptors to fine-tune and coordinate skeletal muscle contractions.
16. The limbic system (often called the emotional brain) includes which group of structures?
Correct Answer: A (Amygdala, hippocampus, and parts of the hypothalamus)
The limbic lobe comprises the amygdala, hippocampus, cingulate gyrus, and connected hypothalamic centers regulating emotion, fear, and long-term memory.
The limbic lobe comprises the amygdala, hippocampus, cingulate gyrus, and connected hypothalamic centers regulating emotion, fear, and long-term memory.
17. Cerebrospinal fluid (CSF) is primarily secreted by specialized vascular structures called:
Correct Answer: B (Choroid plexuses)
Choroid plexuses (vascular tufts lined by modified ependymal cells in the brain ventricles) actively filter and secrete CSF into the ventricular system.
Choroid plexuses (vascular tufts lined by modified ependymal cells in the brain ventricles) actively filter and secrete CSF into the ventricular system.
18. What is the correct sequence of cranial meninges from the outside (skull) to the inside (brain surface)?
Correct Answer: B (Dura mater → Arachnoid mater → Pia mater)
Meninges from superficial to deep: tough fibrous Dura mater → web-like Arachnoid mater → delicate, highly vascular Pia mater adhering to the brain cortex.
Meninges from superficial to deep: tough fibrous Dura mater → web-like Arachnoid mater → delicate, highly vascular Pia mater adhering to the brain cortex.
19. CSF is reabsorbed into the venous bloodstream through:
Correct Answer: A (Arachnoid villi (granulations))
Arachnoid granulations protrude into the superior sagittal dural venous sinus, providing one-way valve drainage for CSF back into systemic circulation.
Arachnoid granulations protrude into the superior sagittal dural venous sinus, providing one-way valve drainage for CSF back into systemic circulation.
20. How many pairs of cranial nerves and spinal nerves are present in humans?
Correct Answer: B (12 pairs cranial, 31 pairs spinal)
Humans possess 12 pairs of cranial nerves originating from the brain/brainstem and 31 pairs of segmentally arranged mixed spinal nerves.
Humans possess 12 pairs of cranial nerves originating from the brain/brainstem and 31 pairs of segmentally arranged mixed spinal nerves.
21. The 10th cranial nerve that provides extensive parasympathetic innervation to visceral organs is the:
Correct Answer: C (Vagus nerve)
Cranial Nerve X (Vagus) is the principal parasympathetic nerve supplying heart, lungs, stomach, pancreas, intestines, and abdominal viscera.
Cranial Nerve X (Vagus) is the principal parasympathetic nerve supplying heart, lungs, stomach, pancreas, intestines, and abdominal viscera.
22. Which cranial nerve is the largest and provides sensory innervation to the face and motor supply to masticatory muscles?
Correct Answer: A (Trigeminal nerve (CN V))
CN V (Trigeminal) splits into ophthalmic (V1), maxillary (V2), and mandibular (V3) branches, providing facial sensation and motor control for chewing.
CN V (Trigeminal) splits into ophthalmic (V1), maxillary (V2), and mandibular (V3) branches, providing facial sensation and motor control for chewing.
23. Broca’s area, responsible for motor speech production, is typically located in the:
Correct Answer: A (Frontal lobe)
Broca’s area resides in the inferior frontal gyrus (typically of the dominant left hemisphere), controlling the motor programs for articulate speech.
Broca’s area resides in the inferior frontal gyrus (typically of the dominant left hemisphere), controlling the motor programs for articulate speech.
24. Wernicke’s area, essential for language comprehension and processing, is located in the:
Correct Answer: B (Temporal lobe)
Wernicke’s area is located primarily in the posterior superior temporal gyrus, playing a vital role in understanding spoken and written words.
Wernicke’s area is located primarily in the posterior superior temporal gyrus, playing a vital role in understanding spoken and written words.
25. In the spinal cord cross-section, the arrangement of gray and white matter is:
Correct Answer: B (Gray matter inside (H-shaped), white matter outside)
Unlike the cerebrum, the spinal cord consists of a central H-shaped gray matter core surrounded by ascending and descending white matter funiculi.
Unlike the cerebrum, the spinal cord consists of a central H-shaped gray matter core surrounded by ascending and descending white matter funiculi.
26. Sensory afferent nerve fibers enter the spinal cord via the:
Correct Answer: A (Dorsal (posterior) root))
According to the Bell-Magendie law, dorsal roots convey sensory impulses into the spinal cord, while ventral roots transmit motor signals outwards.
According to the Bell-Magendie law, dorsal roots convey sensory impulses into the spinal cord, while ventral roots transmit motor signals outwards.
27. The cell bodies of pseudounipolar sensory neurons are situated in the:
Correct Answer: B (Dorsal root ganglion)
Dorsal root ganglia (DRG) house the cell bodies of primary pseudounipolar afferent somatic and visceral sensory neurons.
Dorsal root ganglia (DRG) house the cell bodies of primary pseudounipolar afferent somatic and visceral sensory neurons.
28. Which neuroglial cells form the blood-brain barrier (BBB) by extending perivascular end-feet around capillaries?
Correct Answer: C (Astrocytes)
Astrocytes send pedicles (end-feet) to envelop brain capillary endothelial cells, inducing tight junction formation and maintaining chemical homeostasis.
Astrocytes send pedicles (end-feet) to envelop brain capillary endothelial cells, inducing tight junction formation and maintaining chemical homeostasis.
29. The resident phagocytic macrophages of the Central Nervous System derived from mesoderm are:
Correct Answer: A (Microglia)
Microglia are myeloid-derived glial cells that clear cellular debris, pathogens, and apoptotic neurons in the CNS.
Microglia are myeloid-derived glial cells that clear cellular debris, pathogens, and apoptotic neurons in the CNS.
30. Unipolar neurons (single neurite dividing into two branches) are commonly found in:
Correct Answer: A (Embryonic stages)
True unipolar neurons with a single process extending from the cell body are typical during early embryonic development.
True unipolar neurons with a single process extending from the cell body are typical during early embryonic development.
31. Bipolar neurons possessing one axon and one dendrite are characteristically found in the:
Correct Answer: B (Retina of the eye and olfactory epithelium)
Bipolar neurons are specialized sensory neurons located in the retina, olfactory mucosa, and vestibular/auditory sensory pathways.
Bipolar neurons are specialized sensory neurons located in the retina, olfactory mucosa, and vestibular/auditory sensory pathways.
32. Multipolar neurons (one axon with two or more dendrites) are the dominant neuron type in the:
Correct Answer: A (Cerebral cortex and spinal motor pathways)
Multipolar neurons represent over 99% of all neurons in the human brain, including cortical pyramidal cells and spinal motor neurons.
Multipolar neurons represent over 99% of all neurons in the human brain, including cortical pyramidal cells and spinal motor neurons.
33. The junctional gap between two communicating neurons at a chemical synapse is called the:
Correct Answer: B (Synaptic cleft)
The synaptic cleft is an extracellular fluid space approximately 20 nm wide separating the presynaptic and postsynaptic membranes.
The synaptic cleft is an extracellular fluid space approximately 20 nm wide separating the presynaptic and postsynaptic membranes.
34. Which of the following is an inhibitory neurotransmitter in the mammalian central nervous system?
Correct Answer: B (GABA (Gamma-aminobutyric acid))
GABA and glycine open ligand-gated chloride channels, causing membrane hyperpolarization and generating inhibitory postsynaptic potentials (IPSPs).
GABA and glycine open ligand-gated chloride channels, causing membrane hyperpolarization and generating inhibitory postsynaptic potentials (IPSPs).
35. The major excitatory neurotransmitter in the human brain is:
Correct Answer: A (Glutamate)
Glutamate acts on ionotropic receptors (AMPA, NMDA, kainate) to induce inward Na⁺ and Ca²⁺ currents, mediating excitatory postsynaptic potentials (EPSPs).
Glutamate acts on ionotropic receptors (AMPA, NMDA, kainate) to induce inward Na⁺ and Ca²⁺ currents, mediating excitatory postsynaptic potentials (EPSPs).
36. What is the neurotransmitter released at the mammalian neuromuscular junction (NMJ)?
Correct Answer: B (Acetylcholine (ACh))
Somatic motor axon terminals release acetylcholine into the motor endplate, activating nicotinic acetylcholine receptors to trigger muscle contraction.
Somatic motor axon terminals release acetylcholine into the motor endplate, activating nicotinic acetylcholine receptors to trigger muscle contraction.
37. The enzyme responsible for the rapid degradation of acetylcholine in the synaptic cleft is:
Correct Answer: A (Acetylcholinesterase)
Acetylcholinesterase cleaves ACh into acetate and choline within microseconds, terminating synaptic transmission and preventing tetanic desensitization.
Acetylcholinesterase cleaves ACh into acetate and choline within microseconds, terminating synaptic transmission and preventing tetanic desensitization.
38. In electrical synapses, neurons communicate directly via:
Correct Answer: B (Gap junctions (connexons))
Electrical synapses feature paired hexameric connexon channels creating continuous aqueous pores for instant, bidirectional ionic current flow.
Electrical synapses feature paired hexameric connexon channels creating continuous aqueous pores for instant, bidirectional ionic current flow.
39. The cone-shaped region of the neuron cyton where the axon originates and action potentials are generated is the:
Correct Answer: A (Axon hillock / Initial segment)
The axon initial segment adjacent to the hillock has the lowest threshold for excitation due to the highest local density of voltage-gated Na⁺ channels.
The axon initial segment adjacent to the hillock has the lowest threshold for excitation due to the highest local density of voltage-gated Na⁺ channels.
40. The period during which an axon cannot generate a second action potential under any stimulus strength is called:
Correct Answer: A (Absolute refractory period)
The absolute refractory period is caused by the conformational inactivation of voltage-gated Na⁺ channel inactivation gates (h-gates).
The absolute refractory period is caused by the conformational inactivation of voltage-gated Na⁺ channel inactivation gates (h-gates).
41. The autonomic nervous system consists of two opposing functional divisions:
Correct Answer: B (Sympathetic and Parasympathetic systems)
The autonomic nervous system balances involuntary visceral functions via sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
The autonomic nervous system balances involuntary visceral functions via sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
42. Sympathetic preganglionic neurons originate from which spinal cord regions?
Correct Answer: B (Thoracolumbar outflow (T1 to L2))
Sympathetic preganglionic cell bodies reside in the lateral gray horns of spinal segments T1 through L2 (thoracolumbar division).
Sympathetic preganglionic cell bodies reside in the lateral gray horns of spinal segments T1 through L2 (thoracolumbar division).
43. Parasympathetic outflow is termed craniosacral because preganglionic fibers originate from:
Correct Answer: A (Cranial nerves III, VII, IX, X and sacral segments S2 to S4)
Parasympathetic preganglionic fibers arise from brainstem motor nuclei of CN III, VII, IX, X and the lateral horns of sacral segments S2–S4.
Parasympathetic preganglionic fibers arise from brainstem motor nuclei of CN III, VII, IX, X and the lateral horns of sacral segments S2–S4.
44. Activation of the sympathetic nervous system leads to:
Correct Answer: B (Pupillary dilation (mydriasis) and increased heart rate)
Sympathetic stimulation triggers fight-or-flight responses: pupillary dilation, tachycardia, bronchodilation, and glycogenolysis.
Sympathetic stimulation triggers fight-or-flight responses: pupillary dilation, tachycardia, bronchodilation, and glycogenolysis.
45. The principal postganglionic neurotransmitter released by sympathetic fibers onto target effector organs is:
Correct Answer: B (Norepinephrine (Noradrenaline))
Most postganglionic sympathetic fibers release norepinephrine onto adrenergic receptors (sweat glands being a notable cholinergic exception).
Most postganglionic sympathetic fibers release norepinephrine onto adrenergic receptors (sweat glands being a notable cholinergic exception).
46. What neurotransmitter is released by ALL preganglionic autonomic (sympathetic and parasympathetic) fibers?
Correct Answer: A (Acetylcholine)
All autonomic preganglionic fibers (both sympathetic and parasympathetic) secrete acetylcholine onto nicotinic receptors in autonomic ganglia.
All autonomic preganglionic fibers (both sympathetic and parasympathetic) secrete acetylcholine onto nicotinic receptors in autonomic ganglia.
47. A simple reflex arc consists of the following components in order:
Correct Answer: B (Receptor → Sensory neuron → Integrating center → Motor neuron → Effector)
A neural reflex arc sequence: sensory receptor detects stimulus → afferent neuron → CNS processing center → efferent neuron → effector organ/muscle.
A neural reflex arc sequence: sensory receptor detects stimulus → afferent neuron → CNS processing center → efferent neuron → effector organ/muscle.
48. The knee-jerk (patellar tendon) reflex is an example of a:
Correct Answer: A (Monosynaptic stretch reflex)
Tapping the patellar tendon stretches muscle spindles, firing afferent sensory fibers that directly synapse onto alpha-motor neurons in the spinal cord without interneurons.
Tapping the patellar tendon stretches muscle spindles, firing afferent sensory fibers that directly synapse onto alpha-motor neurons in the spinal cord without interneurons.
49. The blind spot in the human eye is devoid of photoreceptors because it represents:
Correct Answer: B (The optic disc where the optic nerve exits the retina)
At the optic disc, retinal ganglion cell axons converge to form the optic nerve (CN II) and retinal blood vessels penetrate, leaving no space for rods or cones.
At the optic disc, retinal ganglion cell axons converge to form the optic nerve (CN II) and retinal blood vessels penetrate, leaving no space for rods or cones.
50. The yellowish pigmented area of the retina possessing the highest visual acuity is the:
Correct Answer: B (Macula lutea (with Fovea centralis))
The fovea centralis within the macula lutea contains densely packed cone photoreceptors with a 1:1 ganglion cell ratio, yielding maximum visual resolution.
The fovea centralis within the macula lutea contains densely packed cone photoreceptors with a 1:1 ganglion cell ratio, yielding maximum visual resolution.
51. The photopigment rhodopsin present in rod cells consists of:
Correct Answer: A (Opsin (protein) and Retinal (aldehyde derivative of Vitamin A))
Rhodopsin (visual purple) is a conjugated chromoprotein composed of the transmembrane apoprotein scotopsin bound to 11-cis-retinal.
Rhodopsin (visual purple) is a conjugated chromoprotein composed of the transmembrane apoprotein scotopsin bound to 11-cis-retinal.
52. When light strikes rhodopsin in rod photoreceptors, the immediate biochemical event is:
Correct Answer: B (Photoisomerization of 11-cis-retinal to all-trans-retinal)
Photon absorption isomerizes 11-cis-retinal into all-trans-retinal, inducing opsin conformational changes that activate transducin and close cGMP-gated Na⁺ channels (hyperpolarization).
Photon absorption isomerizes 11-cis-retinal into all-trans-retinal, inducing opsin conformational changes that activate transducin and close cGMP-gated Na⁺ channels (hyperpolarization).
53. Daylight (photopic) color vision and high visual acuity are functions mediated by:
Correct Answer: B (Cone cells)
Cones operate under bright photopic illumination and contain photopsin pigments tuned to red (erythrolabe), green (chlorolabe), and blue (cyanolabe) wavelengths.
Cones operate under bright photopic illumination and contain photopsin pigments tuned to red (erythrolabe), green (chlorolabe), and blue (cyanolabe) wavelengths.
54. Aqueous humor fills the anterior and posterior chambers of the eye and is drained through the:
Correct Answer: A (Canal of Schlemm (scleral venous sinus))
Aqueous humor is secreted by the ciliary body processes into the posterior chamber, flows through the pupil, and drains via the trabecular meshwork into the Canal of Schlemm.
Aqueous humor is secreted by the ciliary body processes into the posterior chamber, flows through the pupil, and drains via the trabecular meshwork into the Canal of Schlemm.
55. Glaucoma is a pathological eye condition primarily caused by:
Correct Answer: B (Elevated intraocular pressure due to blocked aqueous humor drainage)
Impaired outflow of aqueous humor elevates intraocular pressure (above 21 mmHg), compressing the retinal microvasculature and causing progressive optic nerve damage.
Impaired outflow of aqueous humor elevates intraocular pressure (above 21 mmHg), compressing the retinal microvasculature and causing progressive optic nerve damage.
56. The correct sequence of middle ear ossicles transmitting acoustic vibrations from the tympanic membrane to the oval window is:
Correct Answer: B (Malleus → Incus → Stapes)
The auditory ossicles chain: Malleus (hammer attached to tympanum) → Incus (anvil) → Stapes (stirrup fitted into fenestra ovalis).
The auditory ossicles chain: Malleus (hammer attached to tympanum) → Incus (anvil) → Stapes (stirrup fitted into fenestra ovalis).
57. The primary sensory receptor organ for hearing located inside the cochlea on the basilar membrane is the:
Correct Answer: C (Organ of Corti)
The Organ of Corti rests on the basilar membrane of the scala media, containing sensory hair cells whose stereocilia brush the tectorial membrane.
The Organ of Corti rests on the basilar membrane of the scala media, containing sensory hair cells whose stereocilia brush the tectorial membrane.
58. The Eustachian tube connects the middle ear cavity with the:
Correct Answer: B (Nasopharynx)
The Eustachian (pharyngotympanic) tube equalizes air pressure between the tympanic cavity and atmospheric air via the nasopharynx.
The Eustachian (pharyngotympanic) tube equalizes air pressure between the tympanic cavity and atmospheric air via the nasopharynx.
59. The dynamic equilibrium of the body during rotational head acceleration is detected by:
Correct Answer: A (Cristae ampullares of semicircular canals)
Cristae ampullares (with gelatinous cupulae) situated in the ampullae of the three semicircular canals respond to angular and rotational deceleration/acceleration.
Cristae ampullares (with gelatinous cupulae) situated in the ampullae of the three semicircular canals respond to angular and rotational deceleration/acceleration.
60. Static equilibrium (linear acceleration and head tilt relative to gravity) is sensed by:
Correct Answer: B (Maculae of the utricle and saccule)
Maculae contain hair cells embedded in an otolithic membrane covered by calcium carbonate crystals (otoliths) that detect linear acceleration and gravity.
Maculae contain hair cells embedded in an otolithic membrane covered by calcium carbonate crystals (otoliths) that detect linear acceleration and gravity.
61. What fluid fills the membranous labyrinth (scala media) of the internal ear?
Correct Answer: B (Endolymph)
Endolymph fills the membranous labyrinth (scala media, utricle, saccule) and is uniquely rich in potassium (K⁺) ions, secreted by the stria vascularis.
Endolymph fills the membranous labyrinth (scala media, utricle, saccule) and is uniquely rich in potassium (K⁺) ions, secreted by the stria vascularis.
62. The bony labyrinth (scala vestibuli and scala tympani) is filled with:
Correct Answer: A (Perilymph)
Perilymph fills the space between the bony labyrinth and membranous labyrinth, with an ionic composition high in Na⁺ and low in K⁺, similar to CSF.
Perilymph fills the space between the bony labyrinth and membranous labyrinth, with an ionic composition high in Na⁺ and low in K⁺, similar to CSF.
63. The tiny calcium carbonate stones embedded in the otolithic membrane of the macula are called:
Correct Answer: B (Otoliths (Otoconia))
Otoliths are dense calcium carbonate crystals that exert inertial drag on the gelatinous layer over macular hair cells during gravitational pull or linear motion.
Otoliths are dense calcium carbonate crystals that exert inertial drag on the gelatinous layer over macular hair cells during gravitational pull or linear motion.
64. The sensory olfactory receptors in humans are:
Correct Answer: B (Primary bipolar neurosensory cells)
Olfactory receptor cells are genuine bipolar neurons whose apical dendrites bear sensory cilia and basal axons form the unmyelinated olfactory nerve (CN I).
Olfactory receptor cells are genuine bipolar neurons whose apical dendrites bear sensory cilia and basal axons form the unmyelinated olfactory nerve (CN I).
65. The olfactory nerve fibers pass through which perforated bone of the skull to reach the olfactory bulb?
Correct Answer: B (Cribriform plate of the ethmoid bone)
Axons of olfactory receptor neurons penetrate the cribriform plate foramina of the ethmoid bone to synapse in the olfactory bulb glomeruli.
Axons of olfactory receptor neurons penetrate the cribriform plate foramina of the ethmoid bone to synapse in the olfactory bulb glomeruli.
66. Taste buds for perceiving the ‘Umami’ basic taste respond specifically to:
Correct Answer: C (L-glutamate and purine ribonucleotides)
Umami (savory) taste transduction is mediated by T1R1/T1R3 GPCR heterodimer receptors that detect monosodium glutamate (MSG) and aspartate.
Umami (savory) taste transduction is mediated by T1R1/T1R3 GPCR heterodimer receptors that detect monosodium glutamate (MSG) and aspartate.
67. The primary sensory relay center for all ascending sensory signals (except olfaction) to the cerebral cortex is the:
Correct Answer: A (Thalamus)
The thalamus acts as the executive sensory switchboard, gating and relaying somatosensory, visual, and auditory information to specific neocortical areas.
The thalamus acts as the executive sensory switchboard, gating and relaying somatosensory, visual, and auditory information to specific neocortical areas.
68. Parkinson’s disease is neurobiologically caused by the progressive degeneration of dopaminergic neurons in the:
Correct Answer: B (Substantia nigra (pars compacta))
Degeneration of pigmented dopaminergic neurons in the midbrain substantia nigra disrupts the nigrostriatal pathway, producing tremors and bradykinesia.
Degeneration of pigmented dopaminergic neurons in the midbrain substantia nigra disrupts the nigrostriatal pathway, producing tremors and bradykinesia.
69. Alzheimer’s disease is histopathologically characterized by:
Correct Answer: B (Extracellular beta-amyloid plaques and intracellular neurofibrillary tau tangles)
Alzheimer’s pathology involves extracellular Aβ peptide aggregation into senile plaques and hyperphosphorylated microtubule-associated tau forming neurofibrillary tangles.
Alzheimer’s pathology involves extracellular Aβ peptide aggregation into senile plaques and hyperphosphorylated microtubule-associated tau forming neurofibrillary tangles.
70. Multiple Sclerosis is a chronic autoimmune disorder characterized by:
Correct Answer: A (Autoimmune destruction of myelin sheaths in the Central Nervous System)
In Multiple Sclerosis, autoreactive T-cells attack CNS myelin sheaths and oligodendrocytes, causing neuroinflammation, conduction block, and sclerosis.
In Multiple Sclerosis, autoreactive T-cells attack CNS myelin sheaths and oligodendrocytes, causing neuroinflammation, conduction block, and sclerosis.
71. Myasthenia gravis is an autoimmune neuromuscular disease caused by antibodies attacking:
Correct Answer: B (Nicotinic acetylcholine receptors at the motor endplate)
Autoantibodies against post-synaptic nicotinic ACh receptors accelerate receptor internalisation and degradation, leading to flaccid muscle fatigue and ptosis.
Autoantibodies against post-synaptic nicotinic ACh receptors accelerate receptor internalisation and degradation, leading to flaccid muscle fatigue and ptosis.
72. Which portion of the human brainstem contains the pneumotaxic center regulating respiration rate?
Correct Answer: B (Pons (Pons Varolii))
The parabrachial nucleus in the upper pons forms the pneumotaxic center, which sends inhibitory impulses to the medullary inspiratory center to limit inspiration.
The parabrachial nucleus in the upper pons forms the pneumotaxic center, which sends inhibitory impulses to the medullary inspiratory center to limit inspiration.
73. The primary visual receiving cortex is located in which lobe of the cerebrum?
Correct Answer: D (Occipital lobe)
The primary visual cortex (Brodmann area 17 / striate cortex) is situated along the banks of the calcarine sulcus in the occipital lobe.
The primary visual cortex (Brodmann area 17 / striate cortex) is situated along the banks of the calcarine sulcus in the occipital lobe.
74. The primary auditory cortex is located in the:
Correct Answer: B (Temporal lobe (Heschl’s gyrus))
Primary auditory receiving cortex (Brodmann areas 41 and 42) resides on the superior temporal gyrus (transverse temporal gyri of Heschl).
Primary auditory receiving cortex (Brodmann areas 41 and 42) resides on the superior temporal gyrus (transverse temporal gyri of Heschl).
75. The primary somatosensory cortex responsible for processing touch, pain, and temperature is located in the:
Correct Answer: B (Postcentral gyrus of parietal lobe)
Somatosensory impulses from the ventral posterolateral thalamus project to the postcentral gyrus (Brodmann areas 3, 1, 2) in the anterior parietal lobe.
Somatosensory impulses from the ventral posterolateral thalamus project to the postcentral gyrus (Brodmann areas 3, 1, 2) in the anterior parietal lobe.
76. The primary motor cortex that initiates voluntary somatic motor commands is located in the:
Correct Answer: A (Precentral gyrus of frontal lobe)
The precentral gyrus (Brodmann area 4) houses giant pyramidal Betz cells whose axons form the descending corticospinal/pyramidal motor tracts.
The precentral gyrus (Brodmann area 4) houses giant pyramidal Betz cells whose axons form the descending corticospinal/pyramidal motor tracts.
77. The pineal gland secretes melatonin, which regulates circadian rhythms. It is an anatomical part of the:
Correct Answer: A (Epithalamus)
The pineal body projects from the posterior epithalamic roof of the third ventricle and converts serotonin to melatonin in darkness.
The pineal body projects from the posterior epithalamic roof of the third ventricle and converts serotonin to melatonin in darkness.
78. The master pacemaker of 24-hour circadian rhythms in mammals is the:
Correct Answer: B (Suprachiasmatic nucleus (SCN) of hypothalamus)
The SCN receives direct retinal projections via the retinohypothalamic tract to synchronize endogenous cellular molecular clocks with external photoperiods.
The SCN receives direct retinal projections via the retinohypothalamic tract to synchronize endogenous cellular molecular clocks with external photoperiods.
79. Which specialized glial cells line the cerebral ventricles and central canal of the spinal cord?
Correct Answer: C (Ependymal cells)
Ependymal cells form a simple cuboidal to columnar ciliated epithelial lining of the ventricles, facilitating the directional circulation of CSF.
Ependymal cells form a simple cuboidal to columnar ciliated epithelial lining of the ventricles, facilitating the directional circulation of CSF.
80. The conical tapering lower terminal end of the adult spinal cord (usually terminating at level L1-L2) is the:
Correct Answer: A (Conus medullaris)
The adult spinal cord tapers between lumbar vertebrae L1 and L2 into the conical conus medullaris, from which the non-neural filum terminale extends.
The adult spinal cord tapers between lumbar vertebrae L1 and L2 into the conical conus medullaris, from which the non-neural filum terminale extends.
81. The delicate, non-neural fibrous filament extending from the tip of the conus medullaris to the coccyx is the:
Correct Answer: B (Filum terminale)
The filum terminale is an extension of pia mater that descends through the lumbar cistern to anchor the dural sac and spinal cord to the coccyx.
The filum terminale is an extension of pia mater that descends through the lumbar cistern to anchor the dural sac and spinal cord to the coccyx.
82. The collection of lumbar, sacral, and coccygeal spinal nerve roots resembling a horse’s tail below L2 is the:
Correct Answer: B (Cauda equina)
Because the adult spinal cord is shorter than the vertebral canal, lower spinal nerve roots descend vertically through the subarachnoid space as the cauda equina.
Because the adult spinal cord is shorter than the vertebral canal, lower spinal nerve roots descend vertically through the subarachnoid space as the cauda equina.
83. Lumbar puncture (spinal tap) for CSF collection is safely performed at which vertebral interspace?
Correct Answer: C (L3 – L4 or L4 – L5)
Below L2, the subarachnoid space contains only cauda equina roots floating in CSF, avoiding spinal cord transfixion during needle puncture.
Below L2, the subarachnoid space contains only cauda equina roots floating in CSF, avoiding spinal cord transfixion during needle puncture.
84. The absolute speed of nerve impulse propagation along an axon is directly proportional to:
Correct Answer: B (Axon diameter and thickness of myelin sheath)
Conduction velocity increases with larger internal axonal diameter (reducing longitudinal electrical resistance) and thicker myelination (reducing membrane capacitance).
Conduction velocity increases with larger internal axonal diameter (reducing longitudinal electrical resistance) and thicker myelination (reducing membrane capacitance).
85. The “All-or-None” law of nerve transmission states that:
Correct Answer: A (A single axon fires at full amplitude or not at all once threshold is reached)
Once threshold depolarization is attained, a complete self-propagating action potential is generated; stimulus strength is encoded by frequency, not amplitude.
Once threshold depolarization is attained, a complete self-propagating action potential is generated; stimulus strength is encoded by frequency, not amplitude.
86. The sensory receptors specialized for detecting muscle stretch and length changes are:
Correct Answer: A (Muscle spindles)
Muscle spindles consist of intrafusal fibers innervated by group Ia and II afferents that detect changes in dynamic and static skeletal muscle length.
Muscle spindles consist of intrafusal fibers innervated by group Ia and II afferents that detect changes in dynamic and static skeletal muscle length.
87. Golgi tendon organs (GTOs) are proprioceptive mechanoreceptors arranged in series that monitor:
Correct Answer: C (Muscle tension and contractile force)
GTOs are encapsulated within myotendinous junctions and fire via Ib afferents in response to active muscle tension, protecting muscles from tear through autogenic inhibition.
GTOs are encapsulated within myotendinous junctions and fire via Ib afferents in response to active muscle tension, protecting muscles from tear through autogenic inhibition.
88. Rapidly adapting mechanoreceptors located deep in the dermis and hypodermis that detect high-frequency vibration and transient pressure are:
Correct Answer: B (Pacinian (lamellar) corpuscles)
Pacinian corpuscles consist of concentric lamellae around a central neurite, adapting rapidly to filter out sustained touch while detecting mechanical vibrations (200-300 Hz).
Pacinian corpuscles consist of concentric lamellae around a central neurite, adapting rapidly to filter out sustained touch while detecting mechanical vibrations (200-300 Hz).
89. Nociceptors are bare nerve endings specialized for perceiving:
Correct Answer: B (Noxious mechanical, thermal, or chemical stimuli (Pain))
Nociceptors are unencapsulated free nerve endings (A-delta and C fibers) that transduce tissue damage into pain signals via release of substance P and glutamate.
Nociceptors are unencapsulated free nerve endings (A-delta and C fibers) that transduce tissue damage into pain signals via release of substance P and glutamate.
90. An action potential arriving at a motor nerve terminal opens which voltage-gated channel to initiate ACh release?
Correct Answer: B (P/Q and N-type Ca²⁺ channels)
Depolarization of the presynaptic terminal opens voltage-gated Ca²⁺ channels, allowing calcium entry to drive vesicle docking and exocytosis.
Depolarization of the presynaptic terminal opens voltage-gated Ca²⁺ channels, allowing calcium entry to drive vesicle docking and exocytosis.
91. Hyperpolarization of a neuronal membrane (making potential more negative than -70 mV) occurs when:
Correct Answer: B (K⁺ channels remain open excessively or Cl⁻ enters the cell)
Hyperpolarization (the undershoot phase) is caused by prolonged opening of voltage-gated K⁺ channels or inhibitory influx of negative Cl⁻ ions.
Hyperpolarization (the undershoot phase) is caused by prolonged opening of voltage-gated K⁺ channels or inhibitory influx of negative Cl⁻ ions.
92. The lateral ventricles of the cerebral hemispheres communicate with the third ventricle via the:
Correct Answer: A (Interventricular foramen (Foramen of Monro))
CSF produced in each lateral ventricle drains through the right and left interventricular foramina of Monro into the midline third ventricle.
CSF produced in each lateral ventricle drains through the right and left interventricular foramina of Monro into the midline third ventricle.
93. The fourth ventricle drains CSF into the subarachnoid space through the:
Correct Answer: C (Median aperture (Magendie) and paired lateral apertures (Luschka))
CSF exits the fourth ventricle into the cerebellomedullary cistern via the single midline foramen of Magendie and two lateral foramina of Luschka.
CSF exits the fourth ventricle into the cerebellomedullary cistern via the single midline foramen of Magendie and two lateral foramina of Luschka.
94. Accommodation of the eye for viewing nearby objects involves:
Correct Answer: A (Contraction of ciliary muscles, slackening of suspensory ligaments, and rounding of the lens)
Parasympathetic ciliary muscle contraction releases tension on zonular fibers (suspensory ligaments), allowing the elastic lens to become more convex and increase refractive power.
Parasympathetic ciliary muscle contraction releases tension on zonular fibers (suspensory ligaments), allowing the elastic lens to become more convex and increase refractive power.
95. Presbyopia is an age-related visual defect resulting from:
Correct Answer: B (Progressive loss of crystalline lens elasticity)
With aging, protein denaturation and sclerosis within the lens reduce its elasticity, impairing near-point accommodation and requiring convex reading lenses.
With aging, protein denaturation and sclerosis within the lens reduce its elasticity, impairing near-point accommodation and requiring convex reading lenses.
96. Astigmatism is an optical refractive error caused by:
Correct Answer: B (Irregular or unequal curvature of the cornea or lens)
In astigmatism, light rays entering the eye across different meridians focus at distinct focal points, corrected with cylindrical lenses.
In astigmatism, light rays entering the eye across different meridians focus at distinct focal points, corrected with cylindrical lenses.
97. Night blindness (Nyctalopia) is caused by:
Correct Answer: A (Dietary deficiency of Vitamin A impairing rhodopsin regeneration)
Vitamin A (retinol) is the direct precursor of 11-cis-retinal. Deficiency impairs rhodopsin resynthesis, causing defective rod vision in dim scotopic light.
Vitamin A (retinol) is the direct precursor of 11-cis-retinal. Deficiency impairs rhodopsin resynthesis, causing defective rod vision in dim scotopic light.
98. Which cranial nerve carries sensory impulses for hearing and balance?
Correct Answer: B (Vestibulocochlear nerve (CN VIII))
Cranial Nerve VIII conveys auditory sensory signals from the cochlear nerve and vestibular equilibrium signals from the vestibular nerve to brainstem nuclei.
Cranial Nerve VIII conveys auditory sensory signals from the cochlear nerve and vestibular equilibrium signals from the vestibular nerve to brainstem nuclei.
99. Which structure secretes the neurohormone oxytocin and vasopressin (ADH)?
Correct Answer: B (Paraventricular and supraoptic nuclei of the hypothalamus)
Magnocellular neurosecretory cells in the supraoptic and paraventricular nuclei synthesize ADH and oxytocin, transporting them down the hypothalamo-hypophyseal tract to the posterior pituitary.
Magnocellular neurosecretory cells in the supraoptic and paraventricular nuclei synthesize ADH and oxytocin, transporting them down the hypothalamo-hypophyseal tract to the posterior pituitary.
100. Spatial and temporal summation of graded potentials occurs primarily at the:
Correct Answer: A (Axon hillock / Initial segment)
Excitatory and inhibitory postsynaptic potentials propagate electrotonically across the soma to the axon hillock, where cumulative net voltage determines if threshold is crossed.
Excitatory and inhibitory postsynaptic potentials propagate electrotonically across the soma to the axon hillock, where cumulative net voltage determines if threshold is crossed.