PCB 3703 Final Exam V2 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Final Exam) | University of Central Florida
1. Which of the following best describes the function of the sodium-potassium pump
(Na+/K+-ATPase) in maintaining the resting membrane potential?
A. It pumps three sodium ions into the cell and two potassium ions out.
B. It pumps three sodium ions out of the cell and two potassium ions into the cell.
C. It pumps equal amounts of sodium and potassium in opposite directions.
D. It allows sodium and potassium to move down their concentration gradients.
Correct Answer: B
Explanation: The Na+/K+-ATPase is an active transport mechanism that moves three Na+
ions out for every two K+ ions moved in. This activity is crucial for maintaining the
electrochemical gradients necessary for excitable cells. The net movement of positive
charge out of the cell contributes slightly to the negative resting membrane potential.
2. In the sliding filament theory of muscle contraction, what occurs during the ‘power
stroke’?
A. ATP binds to the myosin head causing detachment.
B. Calcium binds to troponin to move tropomyosin.
C. The myosin head pivots and pulls the actin filament toward the center of the sarcomere.
,D. The sarcoplasmic reticulum reabsorbs calcium ions.
Correct Answer: C
Explanation: The power stroke occurs when ADP and inorganic phosphate are released
from the myosin head, causing it to pivot. This mechanical action slides the thin actin
filament past the thick myosin filament, shortening the sarcomere. This process is repeated
as long as calcium and ATP are available in the sarcoplasm.
3. Which part of the nephron is primarily responsible for the majority of water and nutrient
reabsorption?
A. Distal convoluted tubule
B. Loop of Henle
C. Proximal convoluted tubule
D. Collecting duct
Correct Answer: C
Explanation: Approximately 65% of the glomerular filtrate is reabsorbed in the proximal
convoluted tubule (PCT). This includes almost all glucose, amino acids, and a significant
portion of electrolytes and water. The PCT cells are highly specialized with microvilli to
increase the surface area for efficient transport.
4. How does increased sympathetic stimulation affect the heart?
A. It increases heart rate and contractility by activating beta-1 adrenergic receptors.
, B. It decreases the heart rate by opening potassium channels.
C. It decreases the force of contraction via the vagus nerve.
D. It causes systemic vasodilation to reduce afterload.
Correct Answer: A
Explanation: Sympathetic nerves release norepinephrine, which binds to beta-1 receptors
on the sinoatrial node and ventricular myocardium. This leads to an increase in the rate of
depolarization (chronotropy) and the strength of contraction (inotropy). The overall effect
is an increase in cardiac output to meet the body’s metabolic demands.
5. Which hormone is primarily responsible for stimulating the release of calcium from bone
when blood calcium levels are low?
A. Calcitonin
B. Thyroxine
C. Parathyroid hormone (PTH)
D. Aldosterone
Correct Answer: C
Explanation: Parathyroid hormone is secreted by the parathyroid glands in response to
hypocalcemia. It acts on osteoclasts to increase bone resorption, thereby releasing calcium
into the bloodstream. Additionally, PTH enhances renal calcium reabsorption and
stimulates the production of active Vitamin D.
Physiology | Actual Q&A with Rationale (PCB3703
Final Exam) | University of Central Florida
1. Which of the following best describes the function of the sodium-potassium pump
(Na+/K+-ATPase) in maintaining the resting membrane potential?
A. It pumps three sodium ions into the cell and two potassium ions out.
B. It pumps three sodium ions out of the cell and two potassium ions into the cell.
C. It pumps equal amounts of sodium and potassium in opposite directions.
D. It allows sodium and potassium to move down their concentration gradients.
Correct Answer: B
Explanation: The Na+/K+-ATPase is an active transport mechanism that moves three Na+
ions out for every two K+ ions moved in. This activity is crucial for maintaining the
electrochemical gradients necessary for excitable cells. The net movement of positive
charge out of the cell contributes slightly to the negative resting membrane potential.
2. In the sliding filament theory of muscle contraction, what occurs during the ‘power
stroke’?
A. ATP binds to the myosin head causing detachment.
B. Calcium binds to troponin to move tropomyosin.
C. The myosin head pivots and pulls the actin filament toward the center of the sarcomere.
,D. The sarcoplasmic reticulum reabsorbs calcium ions.
Correct Answer: C
Explanation: The power stroke occurs when ADP and inorganic phosphate are released
from the myosin head, causing it to pivot. This mechanical action slides the thin actin
filament past the thick myosin filament, shortening the sarcomere. This process is repeated
as long as calcium and ATP are available in the sarcoplasm.
3. Which part of the nephron is primarily responsible for the majority of water and nutrient
reabsorption?
A. Distal convoluted tubule
B. Loop of Henle
C. Proximal convoluted tubule
D. Collecting duct
Correct Answer: C
Explanation: Approximately 65% of the glomerular filtrate is reabsorbed in the proximal
convoluted tubule (PCT). This includes almost all glucose, amino acids, and a significant
portion of electrolytes and water. The PCT cells are highly specialized with microvilli to
increase the surface area for efficient transport.
4. How does increased sympathetic stimulation affect the heart?
A. It increases heart rate and contractility by activating beta-1 adrenergic receptors.
, B. It decreases the heart rate by opening potassium channels.
C. It decreases the force of contraction via the vagus nerve.
D. It causes systemic vasodilation to reduce afterload.
Correct Answer: A
Explanation: Sympathetic nerves release norepinephrine, which binds to beta-1 receptors
on the sinoatrial node and ventricular myocardium. This leads to an increase in the rate of
depolarization (chronotropy) and the strength of contraction (inotropy). The overall effect
is an increase in cardiac output to meet the body’s metabolic demands.
5. Which hormone is primarily responsible for stimulating the release of calcium from bone
when blood calcium levels are low?
A. Calcitonin
B. Thyroxine
C. Parathyroid hormone (PTH)
D. Aldosterone
Correct Answer: C
Explanation: Parathyroid hormone is secreted by the parathyroid glands in response to
hypocalcemia. It acts on osteoclasts to increase bone resorption, thereby releasing calcium
into the bloodstream. Additionally, PTH enhances renal calcium reabsorption and
stimulates the production of active Vitamin D.
