PCB 3703 Exam 2 V1 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Exam 2) | University of Central Florida
1. Which of the following best describes the role of the Na+/K+ ATPase pump in maintaining
the resting membrane potential?
A. It moves 2 sodium ions out and 3 potassium ions in to create a positive charge.
B. It allows for the passive diffusion of ions down their concentration gradients.
C. It transports 3 sodium ions out of the cell and 2 potassium ions into the cell per ATP
molecule.
D. It exclusively transports calcium ions to trigger neurotransmitter release.
Correct Answer: C
Explanation: The Na+/K+ ATPase pump is essential for maintaining the concentration
gradients of sodium and potassium across the cell membrane. By moving three sodium ions
out for every two potassium ions in, it contributes to the electronegativity of the
intracellular environment. This active transport process requires energy in the form of ATP
to move ions against their respective gradients.
2. During the depolarization phase of an action potential, which of the following events
occurs?
A. Potassium channels open, allowing potassium to exit the cell.
B. Voltage-gated sodium channels open, allowing sodium to enter the cell.
,C. The sodium-potassium pump stops functioning entirely.
D. The membrane potential becomes more negative than the resting state.
Correct Answer: B
Explanation: Depolarization is characterized by a rapid shift in membrane potential
toward a more positive value. This is primarily caused by the opening of voltage-gated
sodium channels once the threshold potential is reached. The resulting influx of sodium
ions driven by the electrochemical gradient causes the membrane potential to spike.
3. What is the significance of the absolute refractory period in neuronal signaling?
A. It allows for temporal summation of subthreshold stimuli.
B. It increases the speed of saltatory conduction in unmyelinated axons.
C. It ensures that action potentials propagate in only one direction along the axon.
D. It permits the neuron to fire a second action potential immediately if the stimulus is
strong enough.
Correct Answer: C
Explanation: The absolute refractory period occurs when voltage-gated sodium channels
are either already open or in an inactivated state. During this time, no second action
potential can be generated regardless of stimulus strength. This physiological mechanism
prevents the backward flow of electrical signals and limits the maximum frequency of
action potential firing.
, 4. Saltatory conduction occurs in which type of nerve fibers?
A. Unmyelinated axons within the peripheral nervous system.
B. Dendrites of sensory neurons in the skin.
C. Muscle fibers during the excitation-contraction coupling process.
D. Myelinated axons, where the signal jumps between Nodes of Ranvier.
Correct Answer: D
Explanation: Saltatory conduction is a rapid method of nerve impulse propagation found
in myelinated axons. The insulating myelin sheath prevents ion leakage, allowing the action
potential to ‘jump’ from one Node of Ranvier to the next. This process significantly
increases conduction velocity compared to continuous conduction in unmyelinated fibers.
5. Which ion is primarily responsible for triggering the exocytosis of neurotransmitters from
the presynaptic terminal?
A. Calcium (Ca2+)
B. Potassium (K+)
C. Chloride (Cl-)
D. Sodium (Na+)
Correct Answer: A
Explanation: When an action potential reaches the axon terminal, it triggers the opening of
voltage-gated calcium channels. The influx of calcium ions into the terminal provides the
Physiology | Actual Q&A with Rationale (PCB3703
Exam 2) | University of Central Florida
1. Which of the following best describes the role of the Na+/K+ ATPase pump in maintaining
the resting membrane potential?
A. It moves 2 sodium ions out and 3 potassium ions in to create a positive charge.
B. It allows for the passive diffusion of ions down their concentration gradients.
C. It transports 3 sodium ions out of the cell and 2 potassium ions into the cell per ATP
molecule.
D. It exclusively transports calcium ions to trigger neurotransmitter release.
Correct Answer: C
Explanation: The Na+/K+ ATPase pump is essential for maintaining the concentration
gradients of sodium and potassium across the cell membrane. By moving three sodium ions
out for every two potassium ions in, it contributes to the electronegativity of the
intracellular environment. This active transport process requires energy in the form of ATP
to move ions against their respective gradients.
2. During the depolarization phase of an action potential, which of the following events
occurs?
A. Potassium channels open, allowing potassium to exit the cell.
B. Voltage-gated sodium channels open, allowing sodium to enter the cell.
,C. The sodium-potassium pump stops functioning entirely.
D. The membrane potential becomes more negative than the resting state.
Correct Answer: B
Explanation: Depolarization is characterized by a rapid shift in membrane potential
toward a more positive value. This is primarily caused by the opening of voltage-gated
sodium channels once the threshold potential is reached. The resulting influx of sodium
ions driven by the electrochemical gradient causes the membrane potential to spike.
3. What is the significance of the absolute refractory period in neuronal signaling?
A. It allows for temporal summation of subthreshold stimuli.
B. It increases the speed of saltatory conduction in unmyelinated axons.
C. It ensures that action potentials propagate in only one direction along the axon.
D. It permits the neuron to fire a second action potential immediately if the stimulus is
strong enough.
Correct Answer: C
Explanation: The absolute refractory period occurs when voltage-gated sodium channels
are either already open or in an inactivated state. During this time, no second action
potential can be generated regardless of stimulus strength. This physiological mechanism
prevents the backward flow of electrical signals and limits the maximum frequency of
action potential firing.
, 4. Saltatory conduction occurs in which type of nerve fibers?
A. Unmyelinated axons within the peripheral nervous system.
B. Dendrites of sensory neurons in the skin.
C. Muscle fibers during the excitation-contraction coupling process.
D. Myelinated axons, where the signal jumps between Nodes of Ranvier.
Correct Answer: D
Explanation: Saltatory conduction is a rapid method of nerve impulse propagation found
in myelinated axons. The insulating myelin sheath prevents ion leakage, allowing the action
potential to ‘jump’ from one Node of Ranvier to the next. This process significantly
increases conduction velocity compared to continuous conduction in unmyelinated fibers.
5. Which ion is primarily responsible for triggering the exocytosis of neurotransmitters from
the presynaptic terminal?
A. Calcium (Ca2+)
B. Potassium (K+)
C. Chloride (Cl-)
D. Sodium (Na+)
Correct Answer: A
Explanation: When an action potential reaches the axon terminal, it triggers the opening of
voltage-gated calcium channels. The influx of calcium ions into the terminal provides the
