MDS PREP
What is the primary mechanism by which the pancreas regulates the activity of its own enzymes in the small intestine?
1) By secreting specific enzyme inhibitors
2) By controlling the pH of pancreatic juice
3) By altering the concentration of bile salts
4) Through the action of the sphincter of Oddi
E) By regulating the flow of pancreatic juice into the intestine
The pancreas secretes specific enzyme inhibitors, such as trypsin inhibitor, to prevent the premature activation of pancreatic enzymes in the pancreas itself. These inhibitors are degraded in the duodenum when the enzymes encounter the higher pH, allowing the enzymes to become active and participate in the digestion of food. Additionally, the presence of food in the intestine triggers the release of secretin, which stimulates the pancreas to secrete bicarbonate to neutralize acidic chyme and create an optimal environment for enzyme activity.
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 happens when the corpus luteum regresses during the menstrual cycle?
1) It secrets more estrogen and progesterone
2) It stops secreting estrogen and progesterone
3) It starts secreting FSH and LH
4) It causes an increase in the thickness of the endometrium
When the corpus luteum regresses during the menstrual cycle, it stops secreting estrogen and progesterone, leading to the shedding of the uterine lining.
What is the role of the acrosome in sperm penetration of the egg during fertilization?
1) It produces energy for the sperm's movement
2) It contains enzymes that help dissolve the egg's outer layers
3) It transfers genetic material to the egg
4) It has no role in the penetration process
Physiology
Answer: 2
The acrosome contains enzymes such as hyaluronidase and acrosin that are essential for breaking down the zona pellucida, the egg's outermost layer, allowing the sperm to penetrate and fertilize the egg.
What is the threshold for glucose excretion in the urine in a healthy individual?
1) 100 mg/100 ml
2) 180 mg/100 ml
3) 200 mg/100 ml
4) 250 mg/100 ml
Physiology
Answer: 3
The threshold for glucose excretion is when the plasma glucose reaches approximately 200 mg/100 ml, causing some glucose to be filtered into the urine.
What is the function of cholecystokinin (CCK) in the digestive system?
1) Stimulates the release of bile from the liver
2) Increases the secretion of water in the collecting tubules of the kidney
3) Relaxes the lower esophageal sphincter
4) Decreases the motility of the small intestine
Cholecystokinin (CCK) stimulates the release of bile from the liver and pancreatic enzymes, aiding in digestion.
What is the primary site of vitamin B12 absorption in the intestine?
1) Stomach
2) Duodenum
3) Jejunum
4) Ileum
The primary site of vitamin B12 absorption in the intestine is the ileum, where it binds to intrinsic factor for absorption.
What is the primary function of chymotrypsin in the digestive process?
1) Converting chymotrypsinogen into chymotrypsin
2) Breaking down proteins into peptides
3) Catalyzing the hydrolysis of disulfide bonds in proteins
4) Activating pepsinogen into pepsin
E) Releasing gastrin from gastric mucosa
Chymotrypsin is an endopeptidase enzyme that plays a crucial role in the digestive system by breaking down proteins into smaller peptides. It is activated from its precursor chymotrypsinogen by the enzyme trypsin. Once active, chymotrypsin hydrolyzes the peptide bonds at the carboxyl side of aromatic and bulky amino acids, such as phenylalanine, tryptophan, and tyrosine. This process is essential for the further digestion and absorption of dietary proteins.