PCAT Physiology 5

Question 1

In skeletal muscle, calcium released from the sarcoplasmic reticulum binds to which protein to initiate contraction?

Accepted Answer

Troponin C

Answer

Ca²⁺ binds troponin C, causing a conformational change that moves tropomyosin away from actin's myosin-binding sites, allowing cross-bridge cycling.

Question 2

Which hormone acts on bone to INCREASE osteoclast activity and raise serum calcium?

Accepted Answer

Parathyroid hormone (PTH)

Answer

PTH stimulates osteoclast-mediated bone resorption (via RANKL on osteoblasts), releasing calcium and phosphate into the blood to correct hypocalcemia.

Question 3

The cerebellum contributes to motor coordination primarily by:

Accepted Answer

Comparing intended movement to actual movement and correcting errors

Answer

The cerebellum receives efference copies of motor commands and proprioceptive feedback, computing error signals to fine-tune movement smoothness and timing.

Question 4

In the proximal convoluted tubule, approximately what percentage of filtered sodium is reabsorbed?

Accepted Answer

67%

Answer

About two-thirds (67%) of filtered Na⁺ is reabsorbed in the PCT via Na⁺/H⁺ exchange and cotransport, making it the major site of bulk tubular reabsorption.

Question 5

Which change would increase airway resistance the MOST according to Poiseuille's law?

Accepted Answer

Halving airway radius

Answer

Resistance is inversely proportional to radius to the fourth power (R ∝ 1/r⁴), so halving the radius increases resistance 16-fold—far more than other changes.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Physiology 5