PCAT Physiology 4

Question 1

A patient with SIADH (syndrome of inappropriate ADH secretion) would present with which lab finding?

Accepted Answer

Hyponatremia with concentrated urine

Answer

Excess ADH causes water retention, diluting serum Na⁺ (hyponatremia) while the urine remains inappropriately concentrated due to continued water reabsorption.

Question 2

Which phase of the cardiac cycle is associated with the first heart sound (S1)?

Accepted Answer

Closure of the mitral and tricuspid valves

Answer

S1 is produced by the closure of the AV valves (mitral and tricuspid) at the onset of systole when ventricular pressure exceeds atrial pressure.

Question 3

During inspiration, intrathoracic pressure decreases. This primarily causes:

Accepted Answer

Increased venous return and right heart filling

Answer

Negative intrathoracic pressure during inspiration expands the great veins and right atrium, drawing blood into the thoracic cavity and increasing venous return.

Question 4

The respiratory system's primary defense against acidosis from CO₂ retention is:

Accepted Answer

Increased respiratory rate to blow off CO₂

Answer

Chemoreceptors sense rising PCO₂/falling pH and drive increased ventilation, expiring more CO₂ and rapidly correcting respiratory acidosis.

Question 5

Intestinal glucose absorption against its concentration gradient depends on which cotransport mechanism?

Accepted Answer

Na⁺/glucose cotransporter (SGLT1) powered by Na⁺ gradient

Answer

SGLT1 couples glucose uptake to Na⁺ entry down its electrochemical gradient, which is maintained by basolateral Na⁺/K⁺-ATPase—secondary active transport.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Physiology 4