MDS PREP
What happens to lithocholic acid in the enterohepatic circulation?
1) It is reabsorbed in the terminal ileum and returned to the liver
2) It is metabolized into chenodeoxycholic acid
3) It is converted into deoxycholic acid
4) It is excreted in feces due to its insolubility
Physiology
Answer: 4
Lithocholic acid is insoluble and not efficiently reabsorbed, leading to its excretion in the feces.
What is the primary mechanism by which thyroid hormones increase metabolic rate?
1) Stimulation of the sympathetic nervous system
2) Increased expression of uncoupling proteins
3) Increased activity of the sodium-potassium ATPase pump
4) Stimulation of mitochondrial oxidative phosphorylation
Answer: 4) Stimulation of mitochondrial oxidative phosphorylationExplanation: Thyroid hormones, particularly T3, increase metabolic rate by enhancing the activity of mitochondrial oxidative phosphorylation. This leads to increased ATP production and overall cellular energy metabolism.
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.
What happens to the skin color in dark-skinned patients with high serum bilirubin levels?
1) It turns yellow.
2) It turns green.
3) It remains unaffected.
4) It turns blue.
In dark-skinned patients with high serum bilirubin levels, the skin turns yellow due to the accumulation of bilirubin.
MCQ: Which of the following hormones stimulates the development of the corpus luteum and the secretion of progesterone?
1) Follicle-stimulating hormone (FSH)
2) Luteinizing hormone (LH)
3) Estrogen
4) Progesterone
Luteinizing hormone (LH) stimulates the development of the corpus luteum and the secretion of progesterone, which is crucial for maintaining the uterine lining.
What is the primary function of the theophylline?
1) It acts as a muscle relaxant
2) It increases intracellular cAMP levels
3) It inhibits acetylcholine receptors
4) It stimulates the release of insulin
Theophylline is a methylxanthine derivative that acts as a phosphodiesterase inhibitor, leading to increased intracellular cyclic AMP (cAMP) levels. This can stimulate various cellular processes, including smooth muscle relaxation and bronchodilation in the respiratory system. It also enhances insulin secretion.
What are the main stimuli that increase the secretion of growth hormone (GH)?
1) High blood glucose levels and physical inactivity
2) Hypoglycemia, exercise, protein meals, and stress
3) REM sleep and increased IGF-1 levels
4) High cortisol and fatty acid levels
Answer: 2) Main stimuli that increase GH secretion include hypoglycemia, exercise, protein meals, and stress.
What is the role of leptin in the regulation of food intake?
1) It stimulates food intake
2) It inhibits food intake
3) It has no effect on food intake
4) It increases the absorption of nutrients in the intestine
Physiology
Answer: 2
Leptin is a hormone secreted by adipose tissue that acts on the hypothalamus to inhibit food intake and increase energy expenditure. It plays a key role in regulating body weight and metabolism by signaling satiety and modulating the sensation of hunger and fullness.