MBBS Physiology 2

Question 1

Which segment of the nephron is impermeable to water under all conditions?

Accepted Answer

Thick ascending loop of Henle

Answer

The thick ascending limb of the loop of Henle is always impermeable to water but actively transports NaCl, creating the medullary concentration gradient.

Question 2

What is the normal pH range of arterial blood?

Accepted Answer

7.35–7.45

Answer

Normal arterial blood pH is 7.35–7.45, maintained primarily by the bicarbonate buffer system, lungs, and kidneys.

Question 3

Which hormone causes water reabsorption in the collecting duct by inserting aquaporin-2 channels?

Accepted Answer

Antidiuretic hormone (ADH)

Answer

ADH (vasopressin) binds V2 receptors in the collecting duct, triggering aquaporin-2 insertion and increasing water reabsorption.

Question 4

Which phase of the cardiac action potential is responsible for the plateau in ventricular myocytes?

Accepted Answer

Phase 2 — plateau

Answer

Phase 2 (plateau) is caused by sustained Ca2+ influx through L-type calcium channels balanced by K+ efflux, preventing early repolarization.

Question 5

What is the primary stimulus for erythropoietin (EPO) secretion?

Accepted Answer

Tissue hypoxia detected by renal peritubular cells

Answer

EPO is secreted by peritubular interstitial cells of the kidney in response to tissue hypoxia, mediated by HIF-1α transcription factor.

MBBS - Bachelor of Medicine and Bachelor of Surgery Practice Test

MBBS - Bachelor of Medicine and Bachelor of Surgery Practice Test

MBBS Physiology 2