NBME Physiology 4

Question 1

During the relative refractory period of a neuronal action potential, what stimulus is required to trigger another action potential?

Accepted Answer

A suprathreshold (stronger-than-normal) stimulus

Answer

During the relative refractory period, some K+ channels remain open, raising the threshold so only a suprathreshold stimulus can trigger another action potential.

Question 2

Schwann cells in the peripheral nervous system primarily function to:

Accepted Answer

Myelinate peripheral axons to increase conduction velocity

Answer

Schwann cells wrap peripheral axons in myelin sheaths, enabling saltatory conduction and dramatically increasing action potential propagation speed.

Question 3

A patient presents with hypocalcemia and spontaneous muscle tetany. Deficiency of which hormone is most likely responsible?

Accepted Answer

Parathyroid hormone (PTH)

Answer

PTH deficiency (hypoparathyroidism) reduces calcium reabsorption from bone and kidney, causing hypocalcemia and neuromuscular excitability.

Question 4

Which of the following is a major metabolic effect of cortisol?

Accepted Answer

Increases gluconeogenesis in the liver

Answer

Cortisol stimulates hepatic gluconeogenesis, promotes muscle protein catabolism, and enhances lipolysis, all serving to raise blood glucose during stress.

Question 5

Insulin promotes glucose uptake into skeletal muscle primarily by stimulating translocation of:

Accepted Answer

GLUT4

Answer

Insulin activates PI3K/Akt signaling, causing GLUT4 vesicles to translocate to the plasma membrane of muscle and adipose cells.

NBME Practice Test

NBME Practice Test

NBME Physiology 4