HESI A2 Anatomy & Physiology 2025/2026 – 100% Verified Questions
& Accurate Rationales
Instructions. Correct answer.Rationales reflect 2025/2026
Question 1
The primary function of the mitochondria in eukaryotic cells is:
A. Protein synthesis
B. Lipid storage
C. ATP production via oxidative phosphorylation
D. DNA replication
Rationale: 2025 OpenStax A&P: Mitochondria house the electron transport chain and ATP synthase;
~90% of cellular ATP generated via chemiosmosis.
Question 2
Which tissue type forms the myocardium?
A. Smooth muscle
B. Skeletal muscle
C. Cardiac muscle
D. Dense connective
Rationale: 2025 Guyton Physiology: Cardiac muscle features intercalated discs, branched fibers, and
automaticity; striated but involuntary.
Question 3
The sarcoplasmic reticulum in skeletal muscle primarily stores:
A. Sodium
B. Glucose
C. Calcium ions
D. ATP
Rationale: 2025 HESI A2: Ca²⁺ release from SR triggers actin-myosin cross-bridge cycling; reuptake
causes relaxation.
Question 4
The pacemaker of the heart is the:
A. AV node
B. Bundle of His
C. SA node
D. Purkinje fibers
Rationale: 2025 ECG Physiology: SA node (60–100 bpm) initiates impulse via funny channels (If);
autorhythmic.
Question 5
During ventricular systole, the mitral valve is:
A. Open
B. Partially open
C. Closed
D. Regurgitant
Rationale: 2025 Cardiac Cycle: Isovolumetric contraction → AV valves close (S1); prevents backflow
into atria.
, Question 6
The Frank-Starling law states that stroke volume increases with:
A. Decreased HR
B. Decreased afterload
C. Increased preload (EDV)
D. Increased contractility only
Rationale: 2025 Guyton: Greater venous return → myocardial stretch → stronger contraction
(length-tension relationship).
Question 7
The primary stimulus for erythropoietin release is:
A. Hypernatremia
B. Hypercalcemia
C. Hypoxia (low renal PO₂)
D. Hyperkalemia
Rationale: 2025 Renal Physiology: Peritubular fibroblasts sense hypoxia → EPO → bone marrow RBC
production.
Question 8
The glomerular filtration rate (GFR) is primarily determined by:
A. Oncotic pressure
B. Bowman’s capsule pressure
C. Net filtration pressure (hydrostatic – oncotic)
D. Plasma sodium
Rationale: 2025 Nephron Dynamics: NFP = PGC – (PBS + πGC); normal ~10 mmHg → GFR 125
mL/min.
Question 9
The loop of Henle creates medullary hyperosmolarity via:
A. Active Na⁺ reabsorption in DCT
B. Water reabsorption in PCT
C. Countercurrent multiplication
D. Urea secretion
Rationale: 2025 Urine Concentration: Ascending limb impermeable to water, pumps NaCl → osmotic
gradient (up to 1200 mOsm/L).
Question 10
Aldosterone acts on the:
A. Proximal tubule
B. Loop of Henle
C. Distal convoluted tubule and collecting duct
D. Glomerulus
Rationale: 2025 RAAS: Increases ENaC and Na/K-ATPase → Na⁺ reabsorption, K⁺ secretion; volume
regulation.
Question 11
The primary buffer in extracellular fluid is:
A. Phosphate
B. Protein
& Accurate Rationales
Instructions. Correct answer.Rationales reflect 2025/2026
Question 1
The primary function of the mitochondria in eukaryotic cells is:
A. Protein synthesis
B. Lipid storage
C. ATP production via oxidative phosphorylation
D. DNA replication
Rationale: 2025 OpenStax A&P: Mitochondria house the electron transport chain and ATP synthase;
~90% of cellular ATP generated via chemiosmosis.
Question 2
Which tissue type forms the myocardium?
A. Smooth muscle
B. Skeletal muscle
C. Cardiac muscle
D. Dense connective
Rationale: 2025 Guyton Physiology: Cardiac muscle features intercalated discs, branched fibers, and
automaticity; striated but involuntary.
Question 3
The sarcoplasmic reticulum in skeletal muscle primarily stores:
A. Sodium
B. Glucose
C. Calcium ions
D. ATP
Rationale: 2025 HESI A2: Ca²⁺ release from SR triggers actin-myosin cross-bridge cycling; reuptake
causes relaxation.
Question 4
The pacemaker of the heart is the:
A. AV node
B. Bundle of His
C. SA node
D. Purkinje fibers
Rationale: 2025 ECG Physiology: SA node (60–100 bpm) initiates impulse via funny channels (If);
autorhythmic.
Question 5
During ventricular systole, the mitral valve is:
A. Open
B. Partially open
C. Closed
D. Regurgitant
Rationale: 2025 Cardiac Cycle: Isovolumetric contraction → AV valves close (S1); prevents backflow
into atria.
, Question 6
The Frank-Starling law states that stroke volume increases with:
A. Decreased HR
B. Decreased afterload
C. Increased preload (EDV)
D. Increased contractility only
Rationale: 2025 Guyton: Greater venous return → myocardial stretch → stronger contraction
(length-tension relationship).
Question 7
The primary stimulus for erythropoietin release is:
A. Hypernatremia
B. Hypercalcemia
C. Hypoxia (low renal PO₂)
D. Hyperkalemia
Rationale: 2025 Renal Physiology: Peritubular fibroblasts sense hypoxia → EPO → bone marrow RBC
production.
Question 8
The glomerular filtration rate (GFR) is primarily determined by:
A. Oncotic pressure
B. Bowman’s capsule pressure
C. Net filtration pressure (hydrostatic – oncotic)
D. Plasma sodium
Rationale: 2025 Nephron Dynamics: NFP = PGC – (PBS + πGC); normal ~10 mmHg → GFR 125
mL/min.
Question 9
The loop of Henle creates medullary hyperosmolarity via:
A. Active Na⁺ reabsorption in DCT
B. Water reabsorption in PCT
C. Countercurrent multiplication
D. Urea secretion
Rationale: 2025 Urine Concentration: Ascending limb impermeable to water, pumps NaCl → osmotic
gradient (up to 1200 mOsm/L).
Question 10
Aldosterone acts on the:
A. Proximal tubule
B. Loop of Henle
C. Distal convoluted tubule and collecting duct
D. Glomerulus
Rationale: 2025 RAAS: Increases ENaC and Na/K-ATPase → Na⁺ reabsorption, K⁺ secretion; volume
regulation.
Question 11
The primary buffer in extracellular fluid is:
A. Phosphate
B. Protein
