Human Physiology and Organ System
Physiology Practice Exam questions and
correct answers– Updated 2026 (Graded A+)
instant download pdf
Subject: Physiology
Subtopic: Cellular Physiology
Question 1: A researcher experimentally increases the permeability of a cell membrane to
potassium ions while maintaining all other ion permeabilities constant. Which outcome is most
likely immediately after the intervention?
A) The membrane potential moves closer to the sodium equilibrium potential
B) The membrane potential moves closer to the potassium equilibrium potential
C) The membrane potential becomes exactly 0 mV
D) The membrane potential becomes independent of ion concentration gradients
Correct Answer: B - The membrane potential moves closer to the potassium equilibrium
potential
Rationale: Increasing potassium permeability causes the resting membrane potential to become
more strongly influenced by potassium gradients, shifting it toward the potassium equilibrium
potential as predicted by the Goldman equation. Option A is incorrect because sodium
permeability has not increased. Option C is incorrect because membrane potential rarely
becomes 0 mV under physiologic conditions. Option D is incorrect because ion concentration
gradients remain fundamental determinants of membrane potential.
Question 2: During a prolonged period of fasting, a physiologist observes a decline in
intracellular ATP levels in skeletal muscle. Which membrane transport process would be most
directly impaired?
A) Facilitated diffusion of glucose through GLUT4
B) Osmosis through aquaporins
C) Na+/K+-ATPase activity
D) Diffusion of oxygen across the sarcolemma
Correct Answer: C - Na+/K+-ATPase activity
Rationale: The Na+/K+-ATPase is a primary active transport mechanism requiring ATP
hydrolysis. Reduced ATP availability directly impairs pump function. Facilitated diffusion
through GLUT4 (A) does not directly require ATP. Osmosis (B) and oxygen diffusion (D) are
passive processes driven by gradients rather than ATP.
Question 3: A neuron is repeatedly stimulated at high frequency. Which characteristic of voltage-
gated sodium channels primarily explains the absolute refractory period?
A) Delayed activation kinetics
B) Channel inactivation following opening
C) Progressive potassium accumulation extracellularly
,D) Depletion of intracellular sodium stores
Correct Answer: B - Channel inactivation following opening
Rationale: The absolute refractory period occurs because voltage-gated sodium channels enter
an inactivated state after opening and cannot reopen until repolarization occurs. Delayed
activation (A) is not responsible. Extracellular potassium accumulation (C) may alter excitability
but does not create the absolute refractory period. Sodium depletion (D) is physiologically
insignificant during normal action potentials.
Subtopic: Neurophysiology
Question 4: A patient with demyelinating disease demonstrates markedly reduced nerve
conduction velocity. Which mechanism best explains this finding?
A) Increased membrane capacitance and current leakage
B) Enhanced saltatory conduction
C) Increased neurotransmitter release at synapses
D) Decreased potassium permeability at rest
Correct Answer: A - Increased membrane capacitance and current leakage
Rationale: Myelin normally insulates axons, reducing capacitance and preventing current loss.
Demyelination increases capacitance and current leakage, slowing conduction. Option B is
opposite of the observed phenomenon. Neurotransmitter release (C) does not determine axonal
conduction velocity. Resting potassium permeability (D) is not the primary determinant of
conduction slowing in demyelination.
Question 5: A pharmacologic agent selectively blocks inhibitory interneurons in the spinal cord.
What is the most likely physiologic consequence?
A) Reduced reflex responsiveness
B) Enhanced reflex activity and hyperexcitability
C) Complete loss of skeletal muscle contraction
D) Elimination of sensory transmission
Correct Answer: B - Enhanced reflex activity and hyperexcitability
Rationale: Inhibitory interneurons suppress excessive neuronal firing. Blocking them increases
excitability, often producing exaggerated reflexes. Reduced reflexes (A) would be expected with
impaired excitation. Complete paralysis (C) and loss of sensory transmission (D) require
broader neural dysfunction.
Question 6: A patient experiences damage to the hypothalamus. Which homeostatic function
would most likely be disrupted?
A) Generation of erythrocytes
B) Long-term storage of explicit memories
C) Integration of autonomic and endocrine responses
D) Production of cerebrospinal fluid
Correct Answer: C - Integration of autonomic and endocrine responses
Rationale: The hypothalamus coordinates autonomic, endocrine, thermoregulatory, and
behavioral responses critical for homeostasis. Erythropoiesis (A) primarily occurs in bone
, marrow under renal control. Explicit memory formation (B) involves the hippocampus.
Cerebrospinal fluid production (D) occurs mainly in the choroid plexus.
Subtopic: Muscle Physiology
Question 7: During an experiment, calcium release from the sarcoplasmic reticulum is
completely inhibited in skeletal muscle fibers. Which event would be prevented directly?
A) ATP hydrolysis by myosin heads
B) Exposure of myosin-binding sites on actin
C) Generation of action potentials along the sarcolemma
D) Release of acetylcholine at the neuromuscular junction
Correct Answer: B - Exposure of myosin-binding sites on actin
Rationale: Calcium binds troponin, shifting tropomyosin and exposing actin binding sites.
Without calcium release, cross-bridge formation cannot occur. ATP hydrolysis (A) may still
occur independently. Sarcolemmal action potentials (C) and acetylcholine release (D) occur
upstream of calcium release from the sarcoplasmic reticulum.
Question 8: A patient develops myasthenia gravis characterized by antibodies against nicotinic
acetylcholine receptors. Which physiologic abnormality is expected?
A) Increased end-plate potential amplitude
B) Decreased probability of skeletal muscle action potential generation
C) Excessive calcium release from the sarcoplasmic reticulum
D) Persistent depolarization of muscle fibers
Correct Answer: B - Decreased probability of skeletal muscle action potential generation
Rationale: Fewer functional nicotinic receptors reduce end-plate potentials, making threshold
less likely to be reached. Option A is opposite of the disease mechanism. Excess calcium release
(C) is not characteristic. Persistent depolarization (D) occurs with depolarizing toxins, not
receptor destruction.
Question 9: Which condition would shift skeletal muscle metabolism toward anaerobic
glycolysis during intense exercise?
A) Increased oxygen delivery exceeding demand
B) Decreased ATP utilization
C) Oxygen demand exceeding mitochondrial oxidative capacity
D) Increased fatty acid oxidation efficiency
Correct Answer: C - Oxygen demand exceeding mitochondrial oxidative capacity
Rationale: When ATP demand exceeds aerobic capacity, anaerobic glycolysis increases to
supplement ATP production. Excess oxygen delivery (A) favors aerobic metabolism. Reduced
ATP utilization (B) lowers metabolic requirements. Efficient fatty acid oxidation (D) supports
aerobic metabolism rather than anaerobic glycolysis.
Subtopic: Cardiovascular Physiology
Physiology Practice Exam questions and
correct answers– Updated 2026 (Graded A+)
instant download pdf
Subject: Physiology
Subtopic: Cellular Physiology
Question 1: A researcher experimentally increases the permeability of a cell membrane to
potassium ions while maintaining all other ion permeabilities constant. Which outcome is most
likely immediately after the intervention?
A) The membrane potential moves closer to the sodium equilibrium potential
B) The membrane potential moves closer to the potassium equilibrium potential
C) The membrane potential becomes exactly 0 mV
D) The membrane potential becomes independent of ion concentration gradients
Correct Answer: B - The membrane potential moves closer to the potassium equilibrium
potential
Rationale: Increasing potassium permeability causes the resting membrane potential to become
more strongly influenced by potassium gradients, shifting it toward the potassium equilibrium
potential as predicted by the Goldman equation. Option A is incorrect because sodium
permeability has not increased. Option C is incorrect because membrane potential rarely
becomes 0 mV under physiologic conditions. Option D is incorrect because ion concentration
gradients remain fundamental determinants of membrane potential.
Question 2: During a prolonged period of fasting, a physiologist observes a decline in
intracellular ATP levels in skeletal muscle. Which membrane transport process would be most
directly impaired?
A) Facilitated diffusion of glucose through GLUT4
B) Osmosis through aquaporins
C) Na+/K+-ATPase activity
D) Diffusion of oxygen across the sarcolemma
Correct Answer: C - Na+/K+-ATPase activity
Rationale: The Na+/K+-ATPase is a primary active transport mechanism requiring ATP
hydrolysis. Reduced ATP availability directly impairs pump function. Facilitated diffusion
through GLUT4 (A) does not directly require ATP. Osmosis (B) and oxygen diffusion (D) are
passive processes driven by gradients rather than ATP.
Question 3: A neuron is repeatedly stimulated at high frequency. Which characteristic of voltage-
gated sodium channels primarily explains the absolute refractory period?
A) Delayed activation kinetics
B) Channel inactivation following opening
C) Progressive potassium accumulation extracellularly
,D) Depletion of intracellular sodium stores
Correct Answer: B - Channel inactivation following opening
Rationale: The absolute refractory period occurs because voltage-gated sodium channels enter
an inactivated state after opening and cannot reopen until repolarization occurs. Delayed
activation (A) is not responsible. Extracellular potassium accumulation (C) may alter excitability
but does not create the absolute refractory period. Sodium depletion (D) is physiologically
insignificant during normal action potentials.
Subtopic: Neurophysiology
Question 4: A patient with demyelinating disease demonstrates markedly reduced nerve
conduction velocity. Which mechanism best explains this finding?
A) Increased membrane capacitance and current leakage
B) Enhanced saltatory conduction
C) Increased neurotransmitter release at synapses
D) Decreased potassium permeability at rest
Correct Answer: A - Increased membrane capacitance and current leakage
Rationale: Myelin normally insulates axons, reducing capacitance and preventing current loss.
Demyelination increases capacitance and current leakage, slowing conduction. Option B is
opposite of the observed phenomenon. Neurotransmitter release (C) does not determine axonal
conduction velocity. Resting potassium permeability (D) is not the primary determinant of
conduction slowing in demyelination.
Question 5: A pharmacologic agent selectively blocks inhibitory interneurons in the spinal cord.
What is the most likely physiologic consequence?
A) Reduced reflex responsiveness
B) Enhanced reflex activity and hyperexcitability
C) Complete loss of skeletal muscle contraction
D) Elimination of sensory transmission
Correct Answer: B - Enhanced reflex activity and hyperexcitability
Rationale: Inhibitory interneurons suppress excessive neuronal firing. Blocking them increases
excitability, often producing exaggerated reflexes. Reduced reflexes (A) would be expected with
impaired excitation. Complete paralysis (C) and loss of sensory transmission (D) require
broader neural dysfunction.
Question 6: A patient experiences damage to the hypothalamus. Which homeostatic function
would most likely be disrupted?
A) Generation of erythrocytes
B) Long-term storage of explicit memories
C) Integration of autonomic and endocrine responses
D) Production of cerebrospinal fluid
Correct Answer: C - Integration of autonomic and endocrine responses
Rationale: The hypothalamus coordinates autonomic, endocrine, thermoregulatory, and
behavioral responses critical for homeostasis. Erythropoiesis (A) primarily occurs in bone
, marrow under renal control. Explicit memory formation (B) involves the hippocampus.
Cerebrospinal fluid production (D) occurs mainly in the choroid plexus.
Subtopic: Muscle Physiology
Question 7: During an experiment, calcium release from the sarcoplasmic reticulum is
completely inhibited in skeletal muscle fibers. Which event would be prevented directly?
A) ATP hydrolysis by myosin heads
B) Exposure of myosin-binding sites on actin
C) Generation of action potentials along the sarcolemma
D) Release of acetylcholine at the neuromuscular junction
Correct Answer: B - Exposure of myosin-binding sites on actin
Rationale: Calcium binds troponin, shifting tropomyosin and exposing actin binding sites.
Without calcium release, cross-bridge formation cannot occur. ATP hydrolysis (A) may still
occur independently. Sarcolemmal action potentials (C) and acetylcholine release (D) occur
upstream of calcium release from the sarcoplasmic reticulum.
Question 8: A patient develops myasthenia gravis characterized by antibodies against nicotinic
acetylcholine receptors. Which physiologic abnormality is expected?
A) Increased end-plate potential amplitude
B) Decreased probability of skeletal muscle action potential generation
C) Excessive calcium release from the sarcoplasmic reticulum
D) Persistent depolarization of muscle fibers
Correct Answer: B - Decreased probability of skeletal muscle action potential generation
Rationale: Fewer functional nicotinic receptors reduce end-plate potentials, making threshold
less likely to be reached. Option A is opposite of the disease mechanism. Excess calcium release
(C) is not characteristic. Persistent depolarization (D) occurs with depolarizing toxins, not
receptor destruction.
Question 9: Which condition would shift skeletal muscle metabolism toward anaerobic
glycolysis during intense exercise?
A) Increased oxygen delivery exceeding demand
B) Decreased ATP utilization
C) Oxygen demand exceeding mitochondrial oxidative capacity
D) Increased fatty acid oxidation efficiency
Correct Answer: C - Oxygen demand exceeding mitochondrial oxidative capacity
Rationale: When ATP demand exceeds aerobic capacity, anaerobic glycolysis increases to
supplement ATP production. Excess oxygen delivery (A) favors aerobic metabolism. Reduced
ATP utilization (B) lowers metabolic requirements. Efficient fatty acid oxidation (D) supports
aerobic metabolism rather than anaerobic glycolysis.
Subtopic: Cardiovascular Physiology
