PCB 3703 Exam 2 V3 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Exam 2) | University of Central Florida
1. Which of the following describes the mechanism by which the Absolute Refractory Period
occurs in a neuron?
A. The potassium channels are closed and cannot be reopened by any stimulus.
B. The inactivation gate of the voltage-gated sodium channel is closed and cannot be
opened.
C. The membrane is hyperpolarized, requiring a larger-than-normal stimulus to reach
threshold.
D. Calcium levels within the axon terminal are too low to trigger neurotransmitter release.
Correct Answer: B
Explanation: The absolute refractory period is a critical phase where a second action
potential cannot be generated regardless of stimulus strength. This occurs because the
inactivation gates of the voltage-gated Na+ channels close at the peak of depolarization.
Until the membrane repolarizes and these gates reset to their ‘closed but capable of
opening’ state, the cell remains unresponsive.
2. In skeletal muscle, what is the specific role of Calcium (Ca2+) during the excitation-
contraction coupling process?
A. It binds to Tropomyosin to move it away from the actin binding sites.
,B. It binds to Troponin C, causing a conformational change that shifts Tropomyosin.
C. It enters the cell from the extracellular fluid to trigger the DHP receptor.
D. It binds to the Myosin head to activate the ATPase activity.
Correct Answer: B
Explanation: Calcium is released from the sarcoplasmic reticulum and acts as the primary
signal for contraction in skeletal muscle. It specifically binds to Troponin C, which is part of
the troponin complex. This binding causes a structural shift in the complex, which pulls
tropomyosin off the active sites on the actin filament, allowing myosin to bind.
3. What occurs during the ‘power stroke’ of the cross-bridge cycle?
A. ATP is hydrolyzed into ADP and inorganic phosphate (Pi).
B. ATP binds to the myosin head, causing it to detach from actin.
C. The myosin head is cocked into a high-energy position following ATP hydrolysis.
D. The release of inorganic phosphate (Pi) causes the myosin head to pivot, pulling the
actin filament.
Correct Answer: D
Explanation: The power stroke is the force-generating step of the muscle contraction
cycle. It is triggered by the release of inorganic phosphate from the myosin head after the
cross-bridge has formed. This release causes the myosin head to bend, sliding the thin
filament toward the center of the sarcomere.
, 4. Which region of the brain is primarily responsible for the coordination of complex motor
movements and error correction during motion?
A. Basal Nuclei
B. Hypothalamus
C. Cerebellum
D. Medulla Oblongata
Correct Answer: C
Explanation: The cerebellum acts as a comparator, evaluating the intended movement
from the motor cortex against the actual movement occurring in the limbs. It receives
constant sensory input from proprioceptors and the vestibular system to adjust motor
output. Damage to this area results in ataxia, characterized by clumsy or uncoordinated
movements.
5. During an inhibitory postsynaptic potential (IPSP), which ion movement is most likely
occurring?
A. Potassium (K+) ions exiting the cell.
B. Sodium (Na+) ions entering the cell.
C. Calcium (Ca2+) ions entering the cell.
D. Magnesium (Mg2+) ions exiting the cell.
Correct Answer: A
Physiology | Actual Q&A with Rationale (PCB3703
Exam 2) | University of Central Florida
1. Which of the following describes the mechanism by which the Absolute Refractory Period
occurs in a neuron?
A. The potassium channels are closed and cannot be reopened by any stimulus.
B. The inactivation gate of the voltage-gated sodium channel is closed and cannot be
opened.
C. The membrane is hyperpolarized, requiring a larger-than-normal stimulus to reach
threshold.
D. Calcium levels within the axon terminal are too low to trigger neurotransmitter release.
Correct Answer: B
Explanation: The absolute refractory period is a critical phase where a second action
potential cannot be generated regardless of stimulus strength. This occurs because the
inactivation gates of the voltage-gated Na+ channels close at the peak of depolarization.
Until the membrane repolarizes and these gates reset to their ‘closed but capable of
opening’ state, the cell remains unresponsive.
2. In skeletal muscle, what is the specific role of Calcium (Ca2+) during the excitation-
contraction coupling process?
A. It binds to Tropomyosin to move it away from the actin binding sites.
,B. It binds to Troponin C, causing a conformational change that shifts Tropomyosin.
C. It enters the cell from the extracellular fluid to trigger the DHP receptor.
D. It binds to the Myosin head to activate the ATPase activity.
Correct Answer: B
Explanation: Calcium is released from the sarcoplasmic reticulum and acts as the primary
signal for contraction in skeletal muscle. It specifically binds to Troponin C, which is part of
the troponin complex. This binding causes a structural shift in the complex, which pulls
tropomyosin off the active sites on the actin filament, allowing myosin to bind.
3. What occurs during the ‘power stroke’ of the cross-bridge cycle?
A. ATP is hydrolyzed into ADP and inorganic phosphate (Pi).
B. ATP binds to the myosin head, causing it to detach from actin.
C. The myosin head is cocked into a high-energy position following ATP hydrolysis.
D. The release of inorganic phosphate (Pi) causes the myosin head to pivot, pulling the
actin filament.
Correct Answer: D
Explanation: The power stroke is the force-generating step of the muscle contraction
cycle. It is triggered by the release of inorganic phosphate from the myosin head after the
cross-bridge has formed. This release causes the myosin head to bend, sliding the thin
filament toward the center of the sarcomere.
, 4. Which region of the brain is primarily responsible for the coordination of complex motor
movements and error correction during motion?
A. Basal Nuclei
B. Hypothalamus
C. Cerebellum
D. Medulla Oblongata
Correct Answer: C
Explanation: The cerebellum acts as a comparator, evaluating the intended movement
from the motor cortex against the actual movement occurring in the limbs. It receives
constant sensory input from proprioceptors and the vestibular system to adjust motor
output. Damage to this area results in ataxia, characterized by clumsy or uncoordinated
movements.
5. During an inhibitory postsynaptic potential (IPSP), which ion movement is most likely
occurring?
A. Potassium (K+) ions exiting the cell.
B. Sodium (Na+) ions entering the cell.
C. Calcium (Ca2+) ions entering the cell.
D. Magnesium (Mg2+) ions exiting the cell.
Correct Answer: A
