1|Page
SBU BIO 315 Exam 2026-2027 BANK QUESTIONS WITH
DETAILED VERIFIED ANSWERS EXAM QUESTIONS WILL
COME FROM HERE (100% Latest Already Graded A+
QUESTION 1
In a resting neuron, the membrane potential is primarily established by
which of the following?
A) The sodium-potassium pump directly generating a positive charge
inside the cell
B) The diffusion of potassium ions out of the cell through leak channels
C) The equal distribution of chloride ions across the membrane
D) The active transport of calcium into the endoplasmic reticulum
Answer: B
Explanation: The resting membrane potential is largely determined by
the permeability of the membrane to potassium ions and the
concentration gradient that drives K+ out of the cell. This efflux leaves
behind negatively charged proteins and other anions, creating a
negative interior. The sodium-potassium pump maintains the gradients
but is not the direct source of the potential; it contributes indirectly by
keeping intracellular K+ high. Chloride distribution is not the primary
determinant, and calcium transport is not relevant to the resting
potential in most neurons.
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QUESTION 2
Which of the following best describes an action potential's all-or-none
property?
A) The amplitude of the action potential varies with the strength of the
stimulus
B) Once threshold is reached, the action potential propagates without
decrement
C) The frequency of action potentials is constant regardless of stimulus
intensity
D) Action potentials can be initiated at any point along the axon
Answer: B
Explanation: The all-or-none law states that if a stimulus depolarizes the
membrane to threshold, an action potential of fixed amplitude and
duration will fire and propagate without decreasing in strength. The
amplitude does not vary with stimulus strength; instead, stimulus
intensity is encoded by frequency. Action potentials are normally
initiated at the axon hillock, not at any arbitrary point.
QUESTION 3
Voltage-gated sodium channels are characterized by which of the
following?
A) They open in response to hyperpolarization
B) They have two gates: an activation gate and an inactivation gate
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C) They are exclusively found on dendrites
D) They remain open throughout the absolute refractory period
Answer: B
Explanation: Voltage-gated sodium channels possess an activation gate
that opens upon depolarization and an inactivation gate that closes
shortly thereafter, rendering the channel refractory. They open in
response to depolarization, not hyperpolarization. They are
concentrated at the axon initial segment and nodes of Ranvier. During
the absolute refractory period, the inactivation gate is closed,
preventing reopening.
QUESTION 4
The absolute refractory period is primarily due to:
A) The opening of voltage-gated potassium channels
B) The inactivation of voltage-gated sodium channels
C) The hyperpolarization caused by potassium efflux
D) The closure of leak potassium channels
Answer: B
Explanation: The absolute refractory period coincides with the time
during which voltage-gated sodium channels are inactivated. No
stimulus, regardless of strength, can reopen these channels until they
return to the resting state. While potassium channels contribute to
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repolarization and hyperpolarization, they are not the cause of the
absolute refractory period.
QUESTION 5
Saltatory conduction is characterized by:
A) Continuous propagation of action potentials along the entire axon
membrane
B) Rapid propagation due to action potentials jumping between nodes
of Ranvier
C) Slower conduction due to the presence of myelin
D) Dependence on chemical synapses for transmission
Answer: B
Explanation: Saltatory conduction refers to the "jumping" of action
potentials from one node of Ranvier to the next in myelinated axons.
Myelin insulates the axon, reducing capacitance and increasing
conduction velocity. This is faster than continuous conduction along
unmyelinated fibers. Saltatory conduction does not involve chemical
synapses.
QUESTION 6
Which of the following neurotransmitters is most commonly associated
with neuromuscular junctions in vertebrates?
A) Dopamine
B) Acetylcholine
SBU BIO 315 Exam 2026-2027 BANK QUESTIONS WITH
DETAILED VERIFIED ANSWERS EXAM QUESTIONS WILL
COME FROM HERE (100% Latest Already Graded A+
QUESTION 1
In a resting neuron, the membrane potential is primarily established by
which of the following?
A) The sodium-potassium pump directly generating a positive charge
inside the cell
B) The diffusion of potassium ions out of the cell through leak channels
C) The equal distribution of chloride ions across the membrane
D) The active transport of calcium into the endoplasmic reticulum
Answer: B
Explanation: The resting membrane potential is largely determined by
the permeability of the membrane to potassium ions and the
concentration gradient that drives K+ out of the cell. This efflux leaves
behind negatively charged proteins and other anions, creating a
negative interior. The sodium-potassium pump maintains the gradients
but is not the direct source of the potential; it contributes indirectly by
keeping intracellular K+ high. Chloride distribution is not the primary
determinant, and calcium transport is not relevant to the resting
potential in most neurons.
,2|Page
QUESTION 2
Which of the following best describes an action potential's all-or-none
property?
A) The amplitude of the action potential varies with the strength of the
stimulus
B) Once threshold is reached, the action potential propagates without
decrement
C) The frequency of action potentials is constant regardless of stimulus
intensity
D) Action potentials can be initiated at any point along the axon
Answer: B
Explanation: The all-or-none law states that if a stimulus depolarizes the
membrane to threshold, an action potential of fixed amplitude and
duration will fire and propagate without decreasing in strength. The
amplitude does not vary with stimulus strength; instead, stimulus
intensity is encoded by frequency. Action potentials are normally
initiated at the axon hillock, not at any arbitrary point.
QUESTION 3
Voltage-gated sodium channels are characterized by which of the
following?
A) They open in response to hyperpolarization
B) They have two gates: an activation gate and an inactivation gate
,3|Page
C) They are exclusively found on dendrites
D) They remain open throughout the absolute refractory period
Answer: B
Explanation: Voltage-gated sodium channels possess an activation gate
that opens upon depolarization and an inactivation gate that closes
shortly thereafter, rendering the channel refractory. They open in
response to depolarization, not hyperpolarization. They are
concentrated at the axon initial segment and nodes of Ranvier. During
the absolute refractory period, the inactivation gate is closed,
preventing reopening.
QUESTION 4
The absolute refractory period is primarily due to:
A) The opening of voltage-gated potassium channels
B) The inactivation of voltage-gated sodium channels
C) The hyperpolarization caused by potassium efflux
D) The closure of leak potassium channels
Answer: B
Explanation: The absolute refractory period coincides with the time
during which voltage-gated sodium channels are inactivated. No
stimulus, regardless of strength, can reopen these channels until they
return to the resting state. While potassium channels contribute to
, 4|Page
repolarization and hyperpolarization, they are not the cause of the
absolute refractory period.
QUESTION 5
Saltatory conduction is characterized by:
A) Continuous propagation of action potentials along the entire axon
membrane
B) Rapid propagation due to action potentials jumping between nodes
of Ranvier
C) Slower conduction due to the presence of myelin
D) Dependence on chemical synapses for transmission
Answer: B
Explanation: Saltatory conduction refers to the "jumping" of action
potentials from one node of Ranvier to the next in myelinated axons.
Myelin insulates the axon, reducing capacitance and increasing
conduction velocity. This is faster than continuous conduction along
unmyelinated fibers. Saltatory conduction does not involve chemical
synapses.
QUESTION 6
Which of the following neurotransmitters is most commonly associated
with neuromuscular junctions in vertebrates?
A) Dopamine
B) Acetylcholine
