BIOL 271/BIOL271 Module 4 Comprehensive Exam
Review Actual 2026/2027 with Detailed Rationales | 100%
Verified | Pass Guaranteed
EXAM BLUEPRINT:
● Nervous System – Neural Tissue & Central Nervous System: 18 questions
● Nervous System – Peripheral Nervous System & Autonomic Nervous System: 14
questions
● Special Senses – Vision & Hearing: 12 questions
● Special Senses – Olfaction, Gustation & Equilibrium: 8 questions
● Endocrine System – Glands & Hormones: 13 questions
● TOTAL: 65 questions
SECTION 1: NERVOUS SYSTEM – NEURAL TISSUE & CENTRAL
NERVOUS SYSTEM (Questions 1–18)
Q1: The resting membrane potential of a neuron is approximately:
A. +30 mV
B. 0 mV
C. -70 mV
D. -90 mV
Correct Answer: C
Rationale: Correct because the resting membrane potential of a typical neuron is
approximately -70 mV, maintained by the sodium-potassium pump (3 Na+ out, 2 K+ in)
and the differential permeability of the membrane to K+ ions through leak channels,
creating a negative intracellular charge relative to the extracellular fluid.
Q2: During the depolarization phase of an action potential, which ion channels open and
which ion rushes into the neuron?
A. Potassium channels; K+ enters
,B. Voltage-gated sodium channels; Na+ enters
C. Chloride channels; Cl- enters
D. Calcium channels; Ca2+ enters
Correct Answer: B
Rationale: Correct because when the threshold potential (approximately -55 mV) is
reached, voltage-gated sodium channels rapidly open, allowing Na+ to rush into the
neuron down its electrochemical gradient, causing the membrane potential to reverse to
approximately +30 mV during depolarization.
Q3: The absolute refractory period of a neuron occurs when:
A. The membrane potential is at resting level
B. Voltage-gated Na+ channels are inactivated and cannot be reopened
C. Voltage-gated K+ channels are closed
D. The neuron is hyperpolarized
Correct Answer: B
Rationale: Correct because the absolute refractory period occurs when voltage-gated
Na+ channels have opened and then entered an inactivated state; during this period, no
matter how strong the stimulus, another action potential cannot be generated because
the Na+ channels must return to their resting conformation before they can reopen.
Q4: Saltatory conduction in myelinated axons occurs because:
A. Myelin increases membrane resistance and decreases capacitance, allowing the
action potential to jump between nodes of Ranvier
B. Myelin blocks all ion movement across the membrane
C. The entire axon membrane depolarizes simultaneously
D. Myelin increases the diameter of the axon
Correct Answer: A
Rationale: Correct because myelin, formed by Schwann cells in the PNS and
oligodendrocytes in the CNS, insulates the axon and increases membrane resistance
while decreasing capacitance; this allows the local current to flow rapidly through the
cytoplasm and depolarize the membrane only at the nodes of Ranvier, where
voltage-gated Na+ channels are concentrated, causing the action potential to "jump"
rapidly between nodes.
, Q5: Which neuroglial cell forms the myelin sheath around axons in the central nervous
system?
A. Schwann cells
B. Oligodendrocytes
C. Astrocytes
D. Microglia
Correct Answer: B
Rationale: Correct because oligodendrocytes are the myelinating glial cells of the
central nervous system, with each oligodendrocyte capable of myelinating multiple
axons; this contrasts with Schwann cells, which myelinate single axon segments in the
peripheral nervous system.
Q6: Astrocytes perform which of the following functions in the CNS?
A. Phagocytosis of cellular debris
B. Formation of the blood-brain barrier, regulation of extracellular K+, and provision of
nutrients to neurons
C. Production of cerebrospinal fluid
D. Myelination of axons
Correct Answer: B
Rationale: Correct because astrocytes are the most abundant glial cells in the CNS and
perform multiple supportive functions including forming foot processes that contribute
to the blood-brain barrier, buffering extracellular potassium ions, recycling
neurotransmitters (particularly glutamate), and providing metabolic support and
nutrients to neurons.
Q7: The corpus callosum connects which two structures?
A. The cerebrum and cerebellum
B. The left and right cerebral hemispheres
C. The thalamus and hypothalamus
D. The brainstem and spinal cord
Correct Answer: B
Rationale: Correct because the corpus callosum is the large white matter tract
composed of commissural fibers that connects the left and right cerebral hemispheres,
Review Actual 2026/2027 with Detailed Rationales | 100%
Verified | Pass Guaranteed
EXAM BLUEPRINT:
● Nervous System – Neural Tissue & Central Nervous System: 18 questions
● Nervous System – Peripheral Nervous System & Autonomic Nervous System: 14
questions
● Special Senses – Vision & Hearing: 12 questions
● Special Senses – Olfaction, Gustation & Equilibrium: 8 questions
● Endocrine System – Glands & Hormones: 13 questions
● TOTAL: 65 questions
SECTION 1: NERVOUS SYSTEM – NEURAL TISSUE & CENTRAL
NERVOUS SYSTEM (Questions 1–18)
Q1: The resting membrane potential of a neuron is approximately:
A. +30 mV
B. 0 mV
C. -70 mV
D. -90 mV
Correct Answer: C
Rationale: Correct because the resting membrane potential of a typical neuron is
approximately -70 mV, maintained by the sodium-potassium pump (3 Na+ out, 2 K+ in)
and the differential permeability of the membrane to K+ ions through leak channels,
creating a negative intracellular charge relative to the extracellular fluid.
Q2: During the depolarization phase of an action potential, which ion channels open and
which ion rushes into the neuron?
A. Potassium channels; K+ enters
,B. Voltage-gated sodium channels; Na+ enters
C. Chloride channels; Cl- enters
D. Calcium channels; Ca2+ enters
Correct Answer: B
Rationale: Correct because when the threshold potential (approximately -55 mV) is
reached, voltage-gated sodium channels rapidly open, allowing Na+ to rush into the
neuron down its electrochemical gradient, causing the membrane potential to reverse to
approximately +30 mV during depolarization.
Q3: The absolute refractory period of a neuron occurs when:
A. The membrane potential is at resting level
B. Voltage-gated Na+ channels are inactivated and cannot be reopened
C. Voltage-gated K+ channels are closed
D. The neuron is hyperpolarized
Correct Answer: B
Rationale: Correct because the absolute refractory period occurs when voltage-gated
Na+ channels have opened and then entered an inactivated state; during this period, no
matter how strong the stimulus, another action potential cannot be generated because
the Na+ channels must return to their resting conformation before they can reopen.
Q4: Saltatory conduction in myelinated axons occurs because:
A. Myelin increases membrane resistance and decreases capacitance, allowing the
action potential to jump between nodes of Ranvier
B. Myelin blocks all ion movement across the membrane
C. The entire axon membrane depolarizes simultaneously
D. Myelin increases the diameter of the axon
Correct Answer: A
Rationale: Correct because myelin, formed by Schwann cells in the PNS and
oligodendrocytes in the CNS, insulates the axon and increases membrane resistance
while decreasing capacitance; this allows the local current to flow rapidly through the
cytoplasm and depolarize the membrane only at the nodes of Ranvier, where
voltage-gated Na+ channels are concentrated, causing the action potential to "jump"
rapidly between nodes.
, Q5: Which neuroglial cell forms the myelin sheath around axons in the central nervous
system?
A. Schwann cells
B. Oligodendrocytes
C. Astrocytes
D. Microglia
Correct Answer: B
Rationale: Correct because oligodendrocytes are the myelinating glial cells of the
central nervous system, with each oligodendrocyte capable of myelinating multiple
axons; this contrasts with Schwann cells, which myelinate single axon segments in the
peripheral nervous system.
Q6: Astrocytes perform which of the following functions in the CNS?
A. Phagocytosis of cellular debris
B. Formation of the blood-brain barrier, regulation of extracellular K+, and provision of
nutrients to neurons
C. Production of cerebrospinal fluid
D. Myelination of axons
Correct Answer: B
Rationale: Correct because astrocytes are the most abundant glial cells in the CNS and
perform multiple supportive functions including forming foot processes that contribute
to the blood-brain barrier, buffering extracellular potassium ions, recycling
neurotransmitters (particularly glutamate), and providing metabolic support and
nutrients to neurons.
Q7: The corpus callosum connects which two structures?
A. The cerebrum and cerebellum
B. The left and right cerebral hemispheres
C. The thalamus and hypothalamus
D. The brainstem and spinal cord
Correct Answer: B
Rationale: Correct because the corpus callosum is the large white matter tract
composed of commissural fibers that connects the left and right cerebral hemispheres,
