BIOL251 Human Anatomy & Physiology I
Advanced Exam Prep: Master Nervous
System & Special Senses Practice Questions
& Detailed Explanations
Subject: BIOL251 Module 7 (Nervous System & Special Senses)
Question 1: A patient presents with a localized lesion affecting the postcentral gyrus of the
parietal lobe. Which of the following sensory modalities is most likely to be impaired in the
contralateral side of the body?
A) Proprioception and fine touch
B) Olfactory perception
C) Visual acuity
D) Auditory processing
Correct Answer: A) Proprioception and fine touch
Explanation: The postcentral gyrus serves as the primary somatosensory cortex. It is organized
into a sensory homunculus, receiving input from the thalamus regarding touch, vibration, pain,
temperature, and proprioception. Damage here results in sensory deficits in the contralateral
region of the body map.
Question 2: During the resting membrane potential of a neuron, which ion concentration
gradient is primarily maintained by the Na+/K+-ATPase pump, and what is its net effect
on the intracellular environment?
A) High intracellular Na+, low intracellular K+; net positive charge
B) Low intracellular Na+, high intracellular K+; net negative charge
C) High intracellular Na+, high intracellular K+; neutral charge
D) Low intracellular Na+, low intracellular K+; net negative charge
Correct Answer: B) Low intracellular Na+, high intracellular K+; net negative charge
,Explanation: The Na+/K+-ATPase pump actively transports 3 Na+ ions out of the cell and 2 K+
ions into the cell. This, combined with the higher permeability of the membrane to K+ (leak
channels), maintains a high K+ concentration inside and a negative resting potential.
Question 3: A patient exhibits symptoms of "locked-in syndrome" following a brainstem
stroke. Based on neuroanatomy, which specific region is most likely damaged, and what are
its primary functional roles?
A) Midbrain; regulation of sleep-wake cycles
B) Medulla oblongata; cardiac and respiratory control
C) Pons; corticospinal tract pathway and bridge to cerebellum
D) Thalamus; sensory relay center
Correct Answer: C) Pons; corticospinal tract pathway and bridge to cerebellum
Explanation: Locked-in syndrome typically occurs due to infarction of the ventral pons. The pons
contains the descending corticospinal tracts. Damage here interrupts motor commands to the
spinal cord while often sparing the tegmentum, allowing for preserved ocular movement.
Question 4: In the visual pathway, ganglion cells in the retina project their axons to which
primary thalamic nucleus before reaching the primary visual cortex?
A) Medial geniculate nucleus
B) Lateral geniculate nucleus
C) Ventral posterolateral nucleus
D) Pulvinar nucleus
Correct Answer: B) Lateral geniculate nucleus
Explanation: The lateral geniculate nucleus (LGN) of the thalamus is the specific relay station
for visual information arriving from the optic tract before it is sent to the primary visual cortex
(V1) in the occipital lobe via optic radiations.
Question 5: Which neuroglial cell type is responsible for the formation of the blood-brain
barrier (BBB) by extending perivascular feet to wrap around cerebral capillaries?
A) Oligodendrocyte
B) Microglia
,C) Astrocyte
D) Ependymal cell
Correct Answer: C) Astrocyte
Explanation: Astrocytes are star-shaped glial cells that perform critical homeostatic functions.
Their perivascular feet induce the tight junctions between endothelial cells that comprise the
blood-brain barrier, strictly regulating substance exchange.
Question 6: A deficiency in Vitamin B12 or folic acid can lead to subacute combined
degeneration of the spinal cord. Which sensory pathway is typically affected first,
manifesting as a loss of vibration sense and proprioception?
A) Spinothalamic tract
B) Dorsal column-medial lemniscal pathway
C) Corticospinal tract
D) Spinocerebellar tract
Correct Answer: B) Dorsal column-medial lemniscal pathway
Explanation: The dorsal columns, located in the posterior spinal cord, are susceptible to
metabolic damage. They carry proprioceptive, vibration, and fine touch information. Their
degeneration causes classic ataxia and sensory deficits.
Question 7: During an action potential, the absolute refractory period is primarily caused
by which of the following mechanisms?
A) Inactivation of voltage-gated Na+ channels
B) Slow closing of voltage-gated K+ channels
C) Hyperpolarization of the membrane
D) Increased permeability to Cl- ions
Correct Answer: A) Inactivation of voltage-gated Na+ channels
Explanation: The absolute refractory period occurs during the depolarization and early
repolarization phases. During this time, the voltage-gated Na+ channels are in an inactivated
state (ball-and-chain mechanism) and cannot be reopened regardless of stimulus strength.
, Question 8: Which cranial nerve is responsible for innervating the lateral rectus muscle of
the eye, and what is its specific anatomical pathway?
A) Oculomotor (CN III); exits through the superior orbital fissure
B) Trochlear (CN IV); exits through the superior orbital fissure
C) Abducens (CN VI); exits through the superior orbital fissure
D) Optic (CN II); exits through the optic canal
Correct Answer: C) Abducens (CN VI); exits through the superior orbital fissure
Explanation: The Abducens nerve (CN VI) exclusively innervates the lateral rectus muscle, which
abducts the eye. It emerges from the brainstem at the pontomedullary junction and enters the
orbit via the superior orbital fissure.
Question 9: The sympathetic nervous system utilizes specific neurotransmitters at its
preganglionic and postganglionic synapses. What are they?
A) Acetylcholine (ACh) at both sites
B) Norepinephrine (NE) at both sites
C) ACh at the preganglionic site; NE at the postganglionic site
D) NE at the preganglionic site; ACh at the postganglionic site
Correct Answer: C) ACh at the preganglionic site; NE at the postganglionic site
Explanation: Sympathetic preganglionic fibers are short and release acetylcholine onto nicotinic
receptors. Postganglionic fibers are long and typically release norepinephrine onto adrenergic
receptors on target organs.
Question 10: A patient reports difficulty in identifying objects by touch (astereognosis)
while vision is normal. Which cortical area is likely involved?
A) Primary somatosensory cortex
B) Somatosensory association cortex
C) Primary motor cortex
D) Premotor cortex
Correct Answer: B) Somatosensory association cortex
Advanced Exam Prep: Master Nervous
System & Special Senses Practice Questions
& Detailed Explanations
Subject: BIOL251 Module 7 (Nervous System & Special Senses)
Question 1: A patient presents with a localized lesion affecting the postcentral gyrus of the
parietal lobe. Which of the following sensory modalities is most likely to be impaired in the
contralateral side of the body?
A) Proprioception and fine touch
B) Olfactory perception
C) Visual acuity
D) Auditory processing
Correct Answer: A) Proprioception and fine touch
Explanation: The postcentral gyrus serves as the primary somatosensory cortex. It is organized
into a sensory homunculus, receiving input from the thalamus regarding touch, vibration, pain,
temperature, and proprioception. Damage here results in sensory deficits in the contralateral
region of the body map.
Question 2: During the resting membrane potential of a neuron, which ion concentration
gradient is primarily maintained by the Na+/K+-ATPase pump, and what is its net effect
on the intracellular environment?
A) High intracellular Na+, low intracellular K+; net positive charge
B) Low intracellular Na+, high intracellular K+; net negative charge
C) High intracellular Na+, high intracellular K+; neutral charge
D) Low intracellular Na+, low intracellular K+; net negative charge
Correct Answer: B) Low intracellular Na+, high intracellular K+; net negative charge
,Explanation: The Na+/K+-ATPase pump actively transports 3 Na+ ions out of the cell and 2 K+
ions into the cell. This, combined with the higher permeability of the membrane to K+ (leak
channels), maintains a high K+ concentration inside and a negative resting potential.
Question 3: A patient exhibits symptoms of "locked-in syndrome" following a brainstem
stroke. Based on neuroanatomy, which specific region is most likely damaged, and what are
its primary functional roles?
A) Midbrain; regulation of sleep-wake cycles
B) Medulla oblongata; cardiac and respiratory control
C) Pons; corticospinal tract pathway and bridge to cerebellum
D) Thalamus; sensory relay center
Correct Answer: C) Pons; corticospinal tract pathway and bridge to cerebellum
Explanation: Locked-in syndrome typically occurs due to infarction of the ventral pons. The pons
contains the descending corticospinal tracts. Damage here interrupts motor commands to the
spinal cord while often sparing the tegmentum, allowing for preserved ocular movement.
Question 4: In the visual pathway, ganglion cells in the retina project their axons to which
primary thalamic nucleus before reaching the primary visual cortex?
A) Medial geniculate nucleus
B) Lateral geniculate nucleus
C) Ventral posterolateral nucleus
D) Pulvinar nucleus
Correct Answer: B) Lateral geniculate nucleus
Explanation: The lateral geniculate nucleus (LGN) of the thalamus is the specific relay station
for visual information arriving from the optic tract before it is sent to the primary visual cortex
(V1) in the occipital lobe via optic radiations.
Question 5: Which neuroglial cell type is responsible for the formation of the blood-brain
barrier (BBB) by extending perivascular feet to wrap around cerebral capillaries?
A) Oligodendrocyte
B) Microglia
,C) Astrocyte
D) Ependymal cell
Correct Answer: C) Astrocyte
Explanation: Astrocytes are star-shaped glial cells that perform critical homeostatic functions.
Their perivascular feet induce the tight junctions between endothelial cells that comprise the
blood-brain barrier, strictly regulating substance exchange.
Question 6: A deficiency in Vitamin B12 or folic acid can lead to subacute combined
degeneration of the spinal cord. Which sensory pathway is typically affected first,
manifesting as a loss of vibration sense and proprioception?
A) Spinothalamic tract
B) Dorsal column-medial lemniscal pathway
C) Corticospinal tract
D) Spinocerebellar tract
Correct Answer: B) Dorsal column-medial lemniscal pathway
Explanation: The dorsal columns, located in the posterior spinal cord, are susceptible to
metabolic damage. They carry proprioceptive, vibration, and fine touch information. Their
degeneration causes classic ataxia and sensory deficits.
Question 7: During an action potential, the absolute refractory period is primarily caused
by which of the following mechanisms?
A) Inactivation of voltage-gated Na+ channels
B) Slow closing of voltage-gated K+ channels
C) Hyperpolarization of the membrane
D) Increased permeability to Cl- ions
Correct Answer: A) Inactivation of voltage-gated Na+ channels
Explanation: The absolute refractory period occurs during the depolarization and early
repolarization phases. During this time, the voltage-gated Na+ channels are in an inactivated
state (ball-and-chain mechanism) and cannot be reopened regardless of stimulus strength.
, Question 8: Which cranial nerve is responsible for innervating the lateral rectus muscle of
the eye, and what is its specific anatomical pathway?
A) Oculomotor (CN III); exits through the superior orbital fissure
B) Trochlear (CN IV); exits through the superior orbital fissure
C) Abducens (CN VI); exits through the superior orbital fissure
D) Optic (CN II); exits through the optic canal
Correct Answer: C) Abducens (CN VI); exits through the superior orbital fissure
Explanation: The Abducens nerve (CN VI) exclusively innervates the lateral rectus muscle, which
abducts the eye. It emerges from the brainstem at the pontomedullary junction and enters the
orbit via the superior orbital fissure.
Question 9: The sympathetic nervous system utilizes specific neurotransmitters at its
preganglionic and postganglionic synapses. What are they?
A) Acetylcholine (ACh) at both sites
B) Norepinephrine (NE) at both sites
C) ACh at the preganglionic site; NE at the postganglionic site
D) NE at the preganglionic site; ACh at the postganglionic site
Correct Answer: C) ACh at the preganglionic site; NE at the postganglionic site
Explanation: Sympathetic preganglionic fibers are short and release acetylcholine onto nicotinic
receptors. Postganglionic fibers are long and typically release norepinephrine onto adrenergic
receptors on target organs.
Question 10: A patient reports difficulty in identifying objects by touch (astereognosis)
while vision is normal. Which cortical area is likely involved?
A) Primary somatosensory cortex
B) Somatosensory association cortex
C) Primary motor cortex
D) Premotor cortex
Correct Answer: B) Somatosensory association cortex
