MDS PREP
What is the primary function of bile acids in the intestine?
1) Emulsification of dietary fat
2) Neutralization of intestinal pH
3) Digestion of proteins
4) Absorption of water and electrolytes
Physiology
Answer: 1
Bile acids, through the formation of micelles, aid in the emulsification of fat, facilitating its digestion and absorption.
What is the role of the acrosome in sperm?
1) Provides energy for sperm motility
2) Contains enzymes that help in the penetration of the ovum
3) Protects the sperm DNA
4) Involved in the fertilization process by fusing with the egg membrane
Physiology
Answer: 2
The acrosome is a cap-like structure located on the head of a spermatozoon. It contains lysosome-like organelles rich in enzymes that are essential for penetrating the egg's outer layers during fertilization.
What is the mechanism of action of insulin in increasing glucose uptake by muscle and adipose tissue?
1) Stimulation of sodium-glucose co-transporters (SGLTs)
2) Increase in glucose transporters (GLUT4) on the cell membrane
3) Direct activation of hexokinase
4) Activation of phosphofructokinase
Answer: 2) Increase in glucose transporters (GLUT4) on the cell membraneExplanation: Insulin stimulates the translocation of glucose transporters (specifically GLUT4) from the intracellular vesicles to the cell membrane of muscle and adipose tissue cells. This increases the number of glucose transporters available for glucose uptake, thereby facilitating the influx of glucose into these cells.
What is the primary mechanism by which insulin stimulates glucose uptake in the liver?
1) Induction of glucokinase
2) Increase in glycolysis rate
3) Inhibition of gluconeogenesis
4) Stimulation of glycogenolysis
Answer: 1) Induction of glucokinaseExplanation: Insulin enhances glucose uptake in the liver by inducing the synthesis of glucokinase, an enzyme that converts glucose into glucose-6-phosphate. This "glucose trapping" mechanism keeps intracellular glucose levels low and promotes further glucose entry into the cell.
What is the main mechanism by which the intestinal phase inhibits gastric acid secretion?
1) By releasing hormones that inhibit gastrin release
2) By promoting the release of somatostatin
3) By reducing vagal input to the stomach
4) By increasing the pH of gastric contents
E) By reducing the activity of the myenteric plexus
The intestinal phase of gastric acid secretion is mainly responsible for inhibiting gastric secretion. This is primarily achieved through the release of hormones like secretin and cholecystokinin (CCK) in response to the presence of acidic chyme in the duodenum. These hormones act on D cells in the stomach to reduce gastrin secretion, which in turn decreases acid production by parietal cells. Additionally, the presence of food in the intestine triggers an enterogastric reflex that inhibits the vagal nerve's excitatory effects on the stomach.
What is the osmolarity of the tubular fluid leaving the ascending limb of the loop of Henle?
1) 300mOsm/L
2) 100mOsm/L
3) 1200mOsm/L
4) 50mOsm/L
The osmolarity of the tubular fluid leaving the ascending limb of the loop of Henle is 100mOsm/L, as it is impermeable to water and reabsorbs solutes.
What effect does sympathetic nervous system activation have on renal blood flow (RBF) and glomerular filtration rate (GFR)?
1) Increases RBF and GFR
2) Decreases RBF and increases GFR
3) Decreases RBF and decreases GFR
4) Increases RBF and decreases GFR
E) Has no effect on RBF and GFR
Sympathetic stimulation leads to the constriction of the afferent arterioles, decreasing RBF and GFR. This is part of the body's response to maintain blood pressure and blood volume during stress or hemorrhage.
The rate of gastric emptying is influenced by:
1) The quantity and type of food ingested
2) Distension of the duodenum
3) Gastric hormones like gastrin
4) All of the above
The rate of gastric emptying is influenced by the presence of food in the stomach, the type of food (carbohydrates, proteins, and fats), the distension of the duodenum, and the hormone gastrin, which can increase the rate of emptying.