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.
Which of the following is NOT a secondary bile acid?
1) Cholic acid
2) Deoxycholic acid
3) Lithocholic acid
4) Chenodeoxycholic acid
Physiology
Answer: 1
Cholic acid is a primary bile acid, while deoxycholic acid and lithocholic acid are secondary bile acids formed by bacterial action in the colon.
What is the function of the enteric nervous system?
1) Controls the heart rate and rhythm
2) Regulates the contraction of skeletal muscles
3) Regulates the function of the gastrointestinal tract
4) Controls the pupillary response to light
The enteric nervous system is the intrinsic nervous system of the gastrointestinal tract and is responsible for the regulation of digestion and other gastrointestinal functions. It can operate independently of the central nervous system and consists of a network of neurons and glial cells that are embedded within the wall of the gut, coordinating local reflexes and influencing the muscle and secretory activities of the digestive system.
What type of sleep is associated with sleep spindles and K complexes?
1) Stage 1 NREM
2) Stage 2 NREM
3) Stage 3 NREM
4) REM sleep
While sleep spindles and K complexes are prominent in Stage 2 NREM sleep, they can also be present in the transition between wakefulness and sleep, which is considered part of Stage 1 NREM sleep.
What is the significance of the latch effect in smooth muscle contraction?
1) It allows for rapid contraction and relaxation
2) It prevents the muscle from fully relaxing between contractions
3) It is responsible for the generation of the resting membrane potential
4) It is not relevant to the function of smooth muscles
Answer: 2) It prevents the muscle from fully relaxing between contractionsExplanation: The latch effect in smooth muscles refers to the ability of phosphorylated myosin heads to maintain their attachment to actin filaments even after calcium levels decrease, thus preventing full relaxation without further calcium influx. This sustained contraction with minimal energy expenditure is a characteristic feature of smooth muscles.
What is the role of the area postrema in the regulation of food intake?
1) It senses the presence of food in the stomach
2) It detects the nutritional content of food
3) It is involved in the detection of toxins and the initiation of vomiting
4) It directly stimulates the release of hunger hormones
The area postrema is part of the chemoreceptive trigger zone and detects the presence of toxins in the bloodstream, leading to the initiation of vomiting as a protective mechanism against the ingestion of harmful substances.
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
The threshold for glucose excretion in the urine in a healthy individual is approximately 180 mg/100 ml, above which glucose appears in the urine.
What is the primary neurotransmitter involved in the pupil dilatation during the fight-or-flight response?
1) Acetylcholine
2) Epinephrine
3) Norepinephrine
4) Dopamine
Answer: 2) EpinephrineExplanation: During the fight-or-flight response, epinephrine is released from the adrenal medulla and acts on the pupillary dilator muscles to cause mydriasis (dilatation of pupils). This effect is mediated by beta-adrenergic receptors on the smooth muscle of the iris, leading to increased pupil size to allow more light in for better vision.