MDS PREP
A lowering of serum calcium is the stimulus for the endogenous release of
1. thyroid hormone
2. adrenocortical hormone
3. insulin
4. parathyroid hormone
Physiology Answer: 4
Parathyroid hormone (PTH) levels are mainly controlled by a feedback loop of calcium levels in your blood to your parathyroid glands. In other words, low calcium levels in your blood stimulate parathyroid hormone release, whereas high calcium levels in your blood prevent your glands from releasing parathyroid hormone.
What is the main function of the sodium-potassium-chloride cotransporter in the thick ascending limb of the loop of Henle?
1) To reabsorb sodium and chloride
2) To reabsorb sodium and potassium
3) To reabsorb sodium and secrete hydrogen
4) To reabsorb sodium, potassium, and chloride
E) To reabsorb sodium and hydrogen carbonate
The sodium-potassium-2-chloride (Na+-K+-2Cl-) cotransporter in the thick ascending limb of the loop of Henle is responsible for reabsorbing sodium and chloride ions from the tubular fluid into the blood. This process helps in the maintenance of osmotic balance and the generation of the medullary interstitial gradient.
Which of the following is NOT a hormone secreted by the kidney?
1) 1,25 Dihydrocholecalciferol
2) Renin
3) Erythropoietin
4) Angiotensin I
Angiotensin I is NOT a hormone secreted by the kidney; it is produced from angiotensinogen in the liver and converted to angiotensin II by the kidneys.
What is the role of gastrin in the gastric phase of acid secretion?
1) It is released by the pancreas and stimulates acid secretion in the stomach
2) It is released by the duodenum and inhibits acid secretion
3) It is released by the stomach and stimulates acid secretion in response to food
4) It has no role in gastric acid secretion
Gastrin is released by the stomach and stimulates acid secretion in response to food, playing a key role in the gastric phase of digestion.
What is the result of increased sympathetic nervous system activity on sodium and water reabsorption in the kidney?
1) Decreased sodium and water reabsorption
2) Increased sodium and water reabsorption in the PCT
3) Increased sodium and water reabsorption in the DCT
4) Decreased sodium and water reabsorption in the collecting ducts
E) No effect on sodium and water reabsorption
Sympathetic activity enhances sodium and water reabsorption in the PCT (proximal convoluted tubule) through increased activity of sodium pumps and sodium-potassium-2-chloride cotransporters, which helps in fluid and electrolyte retention.
The main stimulation for production of A.D.H. is
1. Increase in plasma potassium.
2. Decrease in blood volume
3. Increase in extracellular fluid
4. Decrease inextracellularosmotic pressure
Physiology
Answer: 2
The main stimulation for production of A.D.H. is Decrease in blood volume
- A.D.H. secretion increases during osmotic diuresis
Which vitamin is the most important antioxidant in the body, acting in the lipid phase of membranes?
1) Vitamin C
2) Vitamin A
3) Vitamin E (tocopherol)
4) Vitamin B
Vitamin E (tocopherol) is the most important antioxidant in the body, acting in the lipid phase of membranes to protect against oxidative damage.
Which of the following is the primary active transport mechanism for calcium absorption in the intestine?
1) Vitamin D dependent calcium binding protein (calbindin)
2) Sodium-calcium exchanger (NCX)
3) Calcium-dependent ATPase
4) All of the above
Physiology
Answer: 4
Calcium is absorbed mainly in the duodenum and jejunum by an active transport mechanism regulated by 1,25 (OH)2 D3 (calcitriol). It is transported across the brush border of intestinal epithelial cells via TRPV6 channels and binds to calbindin. The absorbed calcium is then delivered to the basolateral membrane by calbindin, and from there it is transported into the bloodstream by either the sodium-calcium exchanger (NCX) or calcium-dependent ATPase.