PCAT Physiology 2

Question 1

Which ion is primarily responsible for the depolarization phase of a cardiac action potential in ventricular myocytes?

Accepted Answer

Sodium (Na⁺)

Answer

Rapid Na⁺ influx through voltage-gated Na⁺ channels causes the sharp depolarization (phase 0) of ventricular action potentials.

Question 2

The Frank-Starling mechanism states that cardiac output increases when:

Accepted Answer

Ventricular end-diastolic volume increases

Answer

Greater ventricular filling (preload) stretches sarcomeres, improving actin-myosin overlap and increasing stroke volume.

Question 3

During exercise, which mechanism most directly increases venous return to the heart?

Accepted Answer

Skeletal muscle pump action

Answer

Rhythmic contraction of skeletal muscles compresses veins and, combined with venous valves, propels blood toward the heart.

Question 4

Aldosterone primarily acts on which nephron segment to regulate sodium reabsorption?

Accepted Answer

Cortical collecting duct

Answer

Aldosterone binds mineralocorticoid receptors in principal cells of the cortical collecting duct, upregulating ENaC and Na⁺/K⁺-ATPase.

Question 5

Which lung volume CANNOT be measured by spirometry alone?

Accepted Answer

Residual volume

Answer

Residual volume is the air remaining after maximal exhalation and requires body plethysmography or helium dilution because it cannot be exhaled into a spirometer.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Physiology 2