PCB 3703 Final Exam V1 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Final Exam) | University of Central Florida
1. During the depolarization phase of an action potential, which of the following events
occurs?
A. Potassium channels open, allowing K+ to leave the cell.
B. Voltage-gated sodium channels open, allowing Na+ to enter the cell.
C. The sodium-potassium pump reverses its direction.
D. The membrane potential becomes more negative than the resting potential.
Correct Answer: B
Explanation: Depolarization is characterized by a rapid influx of sodium ions through
voltage-gated channels. This shift makes the interior of the cell more positive relative to the
outside. Once the threshold is reached, this process becomes self-propagating until peak
voltage is achieved.
2. Which second messenger is primarily associated with the activation of Protein Kinase A
(PKA)?
A. Inositol triphosphate (IP3)
B. Calcium ions (Ca2+)
C. Diacylglycerol (DAG)
,D. Cyclic adenosine monophosphate (cAMP)
Correct Answer: D
Explanation: Adenylate cyclase converts ATP into cAMP in response to certain
extracellular signals. The cAMP then acts as a second messenger to activate Protein Kinase
A, which phosphorylates target proteins. This pathway is a cornerstone of G-protein
coupled receptor signaling in many physiological systems.
3. According to the sliding filament theory, what happens to the A-band during muscle
contraction?
A. It shortens significantly.
B. It lengthens as actin is pulled.
C. It disappears entirely.
D. It remains constant in length.
Correct Answer: D
Explanation: The A-band represents the entire length of the thick myosin filaments.
During contraction, the sarcomere shortens because actin filaments slide past the myosin,
but the myosin filaments themselves do not change length. Thus, the width of the A-band
remains unchanged throughout the process.
4. The Frank-Starling Law of the heart states that:
A. Stroke volume increases in response to an increase in the volume of blood filling the
heart (end diastolic volume).
, B. Cardiac output is inversely proportional to peripheral resistance.
C. The left ventricle is thicker than the right ventricle.
D. Heart rate increases as venous return increases.
Correct Answer: A
Explanation: This physiological principle describes the relationship between end-diastolic
volume and stroke volume. Increased stretching of the cardiac muscle fibers leads to a
more forceful contraction. This ensures that the heart can adjust its output to match the
venous return.
5. Which of the following forces promotes filtration from the glomerular capillaries into
Bowman’s capsule?
A. Glomerular capillary hydrostatic pressure
B. Plasma colloid osmotic pressure
C. Bowman’s capsule hydrostatic pressure
D. Capsular osmotic pressure
Correct Answer: A
Explanation: Glomerular hydrostatic pressure is the primary driving force for filtration in
the nephron. It is opposed by the osmotic pressure of the plasma proteins and the
hydrostatic pressure within the capsule itself. The net filtration pressure determines the
overall Glomerular Filtration Rate (GFR).
Physiology | Actual Q&A with Rationale (PCB3703
Final Exam) | University of Central Florida
1. During the depolarization phase of an action potential, which of the following events
occurs?
A. Potassium channels open, allowing K+ to leave the cell.
B. Voltage-gated sodium channels open, allowing Na+ to enter the cell.
C. The sodium-potassium pump reverses its direction.
D. The membrane potential becomes more negative than the resting potential.
Correct Answer: B
Explanation: Depolarization is characterized by a rapid influx of sodium ions through
voltage-gated channels. This shift makes the interior of the cell more positive relative to the
outside. Once the threshold is reached, this process becomes self-propagating until peak
voltage is achieved.
2. Which second messenger is primarily associated with the activation of Protein Kinase A
(PKA)?
A. Inositol triphosphate (IP3)
B. Calcium ions (Ca2+)
C. Diacylglycerol (DAG)
,D. Cyclic adenosine monophosphate (cAMP)
Correct Answer: D
Explanation: Adenylate cyclase converts ATP into cAMP in response to certain
extracellular signals. The cAMP then acts as a second messenger to activate Protein Kinase
A, which phosphorylates target proteins. This pathway is a cornerstone of G-protein
coupled receptor signaling in many physiological systems.
3. According to the sliding filament theory, what happens to the A-band during muscle
contraction?
A. It shortens significantly.
B. It lengthens as actin is pulled.
C. It disappears entirely.
D. It remains constant in length.
Correct Answer: D
Explanation: The A-band represents the entire length of the thick myosin filaments.
During contraction, the sarcomere shortens because actin filaments slide past the myosin,
but the myosin filaments themselves do not change length. Thus, the width of the A-band
remains unchanged throughout the process.
4. The Frank-Starling Law of the heart states that:
A. Stroke volume increases in response to an increase in the volume of blood filling the
heart (end diastolic volume).
, B. Cardiac output is inversely proportional to peripheral resistance.
C. The left ventricle is thicker than the right ventricle.
D. Heart rate increases as venous return increases.
Correct Answer: A
Explanation: This physiological principle describes the relationship between end-diastolic
volume and stroke volume. Increased stretching of the cardiac muscle fibers leads to a
more forceful contraction. This ensures that the heart can adjust its output to match the
venous return.
5. Which of the following forces promotes filtration from the glomerular capillaries into
Bowman’s capsule?
A. Glomerular capillary hydrostatic pressure
B. Plasma colloid osmotic pressure
C. Bowman’s capsule hydrostatic pressure
D. Capsular osmotic pressure
Correct Answer: A
Explanation: Glomerular hydrostatic pressure is the primary driving force for filtration in
the nephron. It is opposed by the osmotic pressure of the plasma proteins and the
hydrostatic pressure within the capsule itself. The net filtration pressure determines the
overall Glomerular Filtration Rate (GFR).
