BMSC520 Medical Physiology Practice Questions and Answers Updated
2026 | Complete Human Physiology Study Guide with Verified Questions,
Detailed Rationales, Cardiovascular Physiology, Respiratory System,
Renal Physiology, Endocrine Regulation, Nervous System Function,
Homeostasis, Acid-Base Balance, Cellular Physiology & Biomedical
Science Exam Prep
Question 1: Which of the following best describes the primary mechanism by
which insulin facilitates glucose uptake in skeletal muscle and adipose tissue?
A. Activation of adenylate cyclase leading to increased cAMP
B. Translocation of GLUT4 transporters to the plasma membrane
C. Phosphorylation of glycogen synthase kinase-3
D. Inhibition of phosphodiesterase activity
CORRECT ANSWER: B. Translocation of GLUT4 transporters to the plasma
membrane
Rationale: Insulin binding to its receptor triggers a signaling cascade involving IRS-1,
PI3K, and Akt, which ultimately promotes the translocation of intracellular GLUT4
vesicles to the plasma membrane. This increases the capacity for facilitated diffusion of
glucose into insulin-sensitive tissues. Options A, C, and D describe secondary or
unrelated signaling events not directly responsible for acute glucose uptake.
Question 2: During the plateau phase of the cardiac action potential, which ion
current is primarily responsible for maintaining depolarization?
A. Fast Na⁺ influx
B. Delayed rectifier K⁺ efflux
C. L-type Ca²⁺ influx
D. Na⁺/Ca²⁺ exchanger activity
CORRECT ANSWER: C. L-type Ca²⁺ influx
Rationale: The plateau phase (phase 2) of the cardiac myocyte action potential is
sustained by a balance between inward L-type Ca²⁺ current and outward K⁺ currents.
The L-type Ca²⁺ channels open slowly and remain active, allowing Ca²⁺ entry that
maintains depolarization and triggers calcium-induced calcium release from the
sarcoplasmic reticulum. Fast Na⁺ influx occurs during phase 0, while K⁺ efflux
dominates repolarization phases.
Question 3: In the nephron, where is the majority of filtered bicarbonate
reabsorbed?
A. Proximal convoluted tubule
B. Thick ascending limb of Henle
C. Distal convoluted tubule
D. Collecting duct
CORRECT ANSWER: A. Proximal convoluted tubule
,Rationale: Approximately 80-90% of filtered bicarbonate is reabsorbed in the proximal
convoluted tubule via a process involving carbonic anhydrase, Na⁺/H⁺ exchange, and H⁺
secretion. The secreted H⁺ combines with filtered HCO₃⁻ to form H₂CO₃, which
dissociates into CO₂ and H₂O; CO₂ diffuses into the cell and is reconverted to HCO₃⁻ for
basolateral transport. The remaining segments fine-tune acid-base balance but handle
a much smaller fraction.
Question 4: Which of the following hormones directly stimulates the secretion of
gastric acid by parietal cells?
A. Secretin
B. Cholecystokinin
C. Gastrin
D. Somatostatin
CORRECT ANSWER: C. Gastrin
Rationale: Gastrin, released by G cells in the gastric antrum in response to peptides and
gastric distension, binds to CCK-B receptors on parietal cells and directly stimulates H⁺
secretion via H⁺/K⁺ ATPase activation. Secretin and CCK primarily act on the pancreas
and gallbladder, while somatostatin inhibits gastric acid secretion.
Question 5: What is the primary physiological role of surfactant in the alveoli?
A. Enhancing oxygen diffusion across the respiratory membrane
B. Reducing surface tension to prevent alveolar collapse
C. Facilitating CO₂ elimination via increased solubility
D. Activating alveolar macrophages for pathogen clearance
CORRECT ANSWER: B. Reducing surface tension to prevent alveolar collapse
Rationale: Pulmonary surfactant, composed mainly of dipalmitoylphosphatidylcholine
and surfactant proteins, reduces alveolar surface tension according to the Laplace law
(P = 2T/r). This prevents atelectasis, especially during expiration, and promotes lung
compliance. While surfactant has immunomodulatory roles, its primary mechanical
function is surface tension reduction.
Question 6: Which neurotransmitter is primarily responsible for fast inhibitory
postsynaptic potentials (IPSPs) in the central nervous system?
A. Glutamate
B. Dopamine
C. GABA
D. Acetylcholine
CORRECT ANSWER: C. GABA
Rationale: Gamma-aminobutyric acid (GABA) is the principal inhibitory
neurotransmitter in the CNS. Binding to GABA_A receptors opens Cl⁻ channels, causing
hyperpolarization and fast IPSPs. Glutamate mediates fast excitation, dopamine is
,modulatory, and acetylcholine has diverse excitatory and modulatory roles depending
on receptor subtype.
Question 7: During intense exercise, which mechanism is primarily responsible for
the increased oxygen delivery to skeletal muscle?
A. Increased hemoglobin affinity for oxygen
B. Rightward shift of the oxygen-hemoglobin dissociation curve
C. Decreased cardiac output
D. Reduced capillary density in muscle
CORRECT ANSWER: B. Rightward shift of the oxygen-hemoglobin dissociation
curve
Rationale: During exercise, increased temperature, CO₂, H⁺ (decreased pH), and 2,3-
BPG in active muscles cause a rightward shift of the O₂-Hb dissociation curve (Bohr
effect), facilitating oxygen unloading to tissues. Hemoglobin affinity decreases, not
increases; cardiac output increases; and capillary recruitment enhances diffusion, but
the Bohr effect is key for O₂ release.
Question 8: Which of the following best describes the function of the Na⁺/K⁺-
ATPase pump in neuronal resting membrane potential maintenance?
A. It generates the action potential by rapid Na⁺ influx
B. It directly establishes the resting potential by creating ion concentration gradients
C. It terminates synaptic transmission by reuptaking neurotransmitters
D. It buffers intracellular Ca²⁺ during repolarization
CORRECT ANSWER: B. It directly establishes the resting potential by creating ion
concentration gradients
Rationale: The Na⁺/K⁺-ATPase actively transports 3 Na⁺ out and 2 K⁺ into the cell,
establishing the concentration gradients essential for the resting membrane potential.
While the pump is electrogenic (contributing ~-5 mV), the primary resting potential (~-70
mV) arises from K⁺ leak channels. However, without the pump maintaining gradients,
the resting potential could not be sustained.
Question 9: In the renin-angiotensin-aldosterone system (RAAS), what is the
primary stimulus for renin release from juxtaglomerular cells?
A. Increased renal perfusion pressure
B. Elevated plasma angiotensin II levels
C. Decreased NaCl delivery to the macula densa
D. Increased plasma volume
CORRECT ANSWER: C. Decreased NaCl delivery to the macula densa
Rationale: Renin release is stimulated by three main mechanisms: (1) decreased
afferent arteriolar pressure (baroreceptor mechanism), (2) decreased NaCl at the
macula densa (tubuloglomerular feedback), and (3) sympathetic β₁-adrenergic
, activation. Option C directly describes the macula densa mechanism. Increased
perfusion pressure or plasma volume would inhibit renin release.
Question 10: Which of the following accurately describes the role of troponin in
skeletal muscle contraction?
A. It hydrolyzes ATP to provide energy for cross-bridge cycling
B. It binds calcium, causing a conformational change that moves tropomyosin
C. It forms the thick filament and interacts directly with actin
D. It anchors myosin to the Z-disc
CORRECT ANSWER: B. It binds calcium, causing a conformational change that
moves tropomyosin
Rationale: In skeletal muscle, Ca²⁺ released from the sarcoplasmic reticulum binds to
troponin C, inducing a conformational change in the troponin complex that shifts
tropomyosin away from actin's myosin-binding sites, enabling cross-bridge formation.
ATP hydrolysis is performed by myosin ATPase; thick filaments are composed of myosin;
and anchoring involves titin and other proteins.
Question 11: What is the primary site of erythropoietin production in response to
hypoxia?
A. Bone marrow
B. Liver
C. Kidney
D. Spleen
CORRECT ANSWER: C. Kidney
Rationale: In adults, the kidney (specifically peritubular interstitial cells) is the primary
source of erythropoietin (EPO) in response to tissue hypoxia. The liver produces EPO
during fetal development and can contribute in adults under certain conditions, but
renal production dominates physiological regulation. Bone marrow is the site of
erythropoiesis, not EPO synthesis.
Question 12: Which of the following best explains why the action potential in
cardiac muscle has a prolonged refractory period compared to skeletal muscle?
A. Faster inactivation of voltage-gated Na⁺ channels
B. Sustained Ca²⁺ influx through L-type channels during the plateau
C. Higher density of K⁺ leak channels
D. Absence of T-tubules in cardiac myocytes
CORRECT ANSWER: B. Sustained Ca²⁺ influx through L-type channels during the
plateau
Rationale: The cardiac action potential plateau (phase 2) is maintained by L-type Ca²⁺
channel activity, which delays repolarization and extends the absolute refractory
period. This prevents tetany and allows the heart to fill between contractions. Skeletal
2026 | Complete Human Physiology Study Guide with Verified Questions,
Detailed Rationales, Cardiovascular Physiology, Respiratory System,
Renal Physiology, Endocrine Regulation, Nervous System Function,
Homeostasis, Acid-Base Balance, Cellular Physiology & Biomedical
Science Exam Prep
Question 1: Which of the following best describes the primary mechanism by
which insulin facilitates glucose uptake in skeletal muscle and adipose tissue?
A. Activation of adenylate cyclase leading to increased cAMP
B. Translocation of GLUT4 transporters to the plasma membrane
C. Phosphorylation of glycogen synthase kinase-3
D. Inhibition of phosphodiesterase activity
CORRECT ANSWER: B. Translocation of GLUT4 transporters to the plasma
membrane
Rationale: Insulin binding to its receptor triggers a signaling cascade involving IRS-1,
PI3K, and Akt, which ultimately promotes the translocation of intracellular GLUT4
vesicles to the plasma membrane. This increases the capacity for facilitated diffusion of
glucose into insulin-sensitive tissues. Options A, C, and D describe secondary or
unrelated signaling events not directly responsible for acute glucose uptake.
Question 2: During the plateau phase of the cardiac action potential, which ion
current is primarily responsible for maintaining depolarization?
A. Fast Na⁺ influx
B. Delayed rectifier K⁺ efflux
C. L-type Ca²⁺ influx
D. Na⁺/Ca²⁺ exchanger activity
CORRECT ANSWER: C. L-type Ca²⁺ influx
Rationale: The plateau phase (phase 2) of the cardiac myocyte action potential is
sustained by a balance between inward L-type Ca²⁺ current and outward K⁺ currents.
The L-type Ca²⁺ channels open slowly and remain active, allowing Ca²⁺ entry that
maintains depolarization and triggers calcium-induced calcium release from the
sarcoplasmic reticulum. Fast Na⁺ influx occurs during phase 0, while K⁺ efflux
dominates repolarization phases.
Question 3: In the nephron, where is the majority of filtered bicarbonate
reabsorbed?
A. Proximal convoluted tubule
B. Thick ascending limb of Henle
C. Distal convoluted tubule
D. Collecting duct
CORRECT ANSWER: A. Proximal convoluted tubule
,Rationale: Approximately 80-90% of filtered bicarbonate is reabsorbed in the proximal
convoluted tubule via a process involving carbonic anhydrase, Na⁺/H⁺ exchange, and H⁺
secretion. The secreted H⁺ combines with filtered HCO₃⁻ to form H₂CO₃, which
dissociates into CO₂ and H₂O; CO₂ diffuses into the cell and is reconverted to HCO₃⁻ for
basolateral transport. The remaining segments fine-tune acid-base balance but handle
a much smaller fraction.
Question 4: Which of the following hormones directly stimulates the secretion of
gastric acid by parietal cells?
A. Secretin
B. Cholecystokinin
C. Gastrin
D. Somatostatin
CORRECT ANSWER: C. Gastrin
Rationale: Gastrin, released by G cells in the gastric antrum in response to peptides and
gastric distension, binds to CCK-B receptors on parietal cells and directly stimulates H⁺
secretion via H⁺/K⁺ ATPase activation. Secretin and CCK primarily act on the pancreas
and gallbladder, while somatostatin inhibits gastric acid secretion.
Question 5: What is the primary physiological role of surfactant in the alveoli?
A. Enhancing oxygen diffusion across the respiratory membrane
B. Reducing surface tension to prevent alveolar collapse
C. Facilitating CO₂ elimination via increased solubility
D. Activating alveolar macrophages for pathogen clearance
CORRECT ANSWER: B. Reducing surface tension to prevent alveolar collapse
Rationale: Pulmonary surfactant, composed mainly of dipalmitoylphosphatidylcholine
and surfactant proteins, reduces alveolar surface tension according to the Laplace law
(P = 2T/r). This prevents atelectasis, especially during expiration, and promotes lung
compliance. While surfactant has immunomodulatory roles, its primary mechanical
function is surface tension reduction.
Question 6: Which neurotransmitter is primarily responsible for fast inhibitory
postsynaptic potentials (IPSPs) in the central nervous system?
A. Glutamate
B. Dopamine
C. GABA
D. Acetylcholine
CORRECT ANSWER: C. GABA
Rationale: Gamma-aminobutyric acid (GABA) is the principal inhibitory
neurotransmitter in the CNS. Binding to GABA_A receptors opens Cl⁻ channels, causing
hyperpolarization and fast IPSPs. Glutamate mediates fast excitation, dopamine is
,modulatory, and acetylcholine has diverse excitatory and modulatory roles depending
on receptor subtype.
Question 7: During intense exercise, which mechanism is primarily responsible for
the increased oxygen delivery to skeletal muscle?
A. Increased hemoglobin affinity for oxygen
B. Rightward shift of the oxygen-hemoglobin dissociation curve
C. Decreased cardiac output
D. Reduced capillary density in muscle
CORRECT ANSWER: B. Rightward shift of the oxygen-hemoglobin dissociation
curve
Rationale: During exercise, increased temperature, CO₂, H⁺ (decreased pH), and 2,3-
BPG in active muscles cause a rightward shift of the O₂-Hb dissociation curve (Bohr
effect), facilitating oxygen unloading to tissues. Hemoglobin affinity decreases, not
increases; cardiac output increases; and capillary recruitment enhances diffusion, but
the Bohr effect is key for O₂ release.
Question 8: Which of the following best describes the function of the Na⁺/K⁺-
ATPase pump in neuronal resting membrane potential maintenance?
A. It generates the action potential by rapid Na⁺ influx
B. It directly establishes the resting potential by creating ion concentration gradients
C. It terminates synaptic transmission by reuptaking neurotransmitters
D. It buffers intracellular Ca²⁺ during repolarization
CORRECT ANSWER: B. It directly establishes the resting potential by creating ion
concentration gradients
Rationale: The Na⁺/K⁺-ATPase actively transports 3 Na⁺ out and 2 K⁺ into the cell,
establishing the concentration gradients essential for the resting membrane potential.
While the pump is electrogenic (contributing ~-5 mV), the primary resting potential (~-70
mV) arises from K⁺ leak channels. However, without the pump maintaining gradients,
the resting potential could not be sustained.
Question 9: In the renin-angiotensin-aldosterone system (RAAS), what is the
primary stimulus for renin release from juxtaglomerular cells?
A. Increased renal perfusion pressure
B. Elevated plasma angiotensin II levels
C. Decreased NaCl delivery to the macula densa
D. Increased plasma volume
CORRECT ANSWER: C. Decreased NaCl delivery to the macula densa
Rationale: Renin release is stimulated by three main mechanisms: (1) decreased
afferent arteriolar pressure (baroreceptor mechanism), (2) decreased NaCl at the
macula densa (tubuloglomerular feedback), and (3) sympathetic β₁-adrenergic
, activation. Option C directly describes the macula densa mechanism. Increased
perfusion pressure or plasma volume would inhibit renin release.
Question 10: Which of the following accurately describes the role of troponin in
skeletal muscle contraction?
A. It hydrolyzes ATP to provide energy for cross-bridge cycling
B. It binds calcium, causing a conformational change that moves tropomyosin
C. It forms the thick filament and interacts directly with actin
D. It anchors myosin to the Z-disc
CORRECT ANSWER: B. It binds calcium, causing a conformational change that
moves tropomyosin
Rationale: In skeletal muscle, Ca²⁺ released from the sarcoplasmic reticulum binds to
troponin C, inducing a conformational change in the troponin complex that shifts
tropomyosin away from actin's myosin-binding sites, enabling cross-bridge formation.
ATP hydrolysis is performed by myosin ATPase; thick filaments are composed of myosin;
and anchoring involves titin and other proteins.
Question 11: What is the primary site of erythropoietin production in response to
hypoxia?
A. Bone marrow
B. Liver
C. Kidney
D. Spleen
CORRECT ANSWER: C. Kidney
Rationale: In adults, the kidney (specifically peritubular interstitial cells) is the primary
source of erythropoietin (EPO) in response to tissue hypoxia. The liver produces EPO
during fetal development and can contribute in adults under certain conditions, but
renal production dominates physiological regulation. Bone marrow is the site of
erythropoiesis, not EPO synthesis.
Question 12: Which of the following best explains why the action potential in
cardiac muscle has a prolonged refractory period compared to skeletal muscle?
A. Faster inactivation of voltage-gated Na⁺ channels
B. Sustained Ca²⁺ influx through L-type channels during the plateau
C. Higher density of K⁺ leak channels
D. Absence of T-tubules in cardiac myocytes
CORRECT ANSWER: B. Sustained Ca²⁺ influx through L-type channels during the
plateau
Rationale: The cardiac action potential plateau (phase 2) is maintained by L-type Ca²⁺
channel activity, which delays repolarization and extends the absolute refractory
period. This prevents tetany and allows the heart to fill between contractions. Skeletal
