MDS PREP
What is the primary function of the C-peptide after it is cleaved from proinsulin during the synthesis of insulin?
1) It has no significant role
2) It acts as a regulator of insulin secretion
3) It serves as a precursor for other pancreatic hormones
4) It is involved in the maintenance of islet cell structure
The C-peptide is removed during the conversion of proinsulin to insulin and does not have a known biological function. Its primary purpose is to hold the A and B chains of proinsulin together during synthesis.
What is the function of calcidiol in the body?
1) It is the active form of vitamin D
2) It is the precursor to calcitriol (active vitamin D)
3) It has no known function
4) It inhibits calcium absorption
Physiology
Answer: 2
Calcidiol (25 hydroxy cholecalciferol) is a precursor to calcitriol (1,25 dihydroxy vitamin D3), which is the active form of vitamin D. Calcitriol is formed in the kidneys by the action of 1-? hydroxylase and plays a critical role in calcium homeostasis.
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 primary effect of norepinephrine on blood vessels during the fight-or-flight response?
1) Vasodilatation in most vessels
2) Vasoconstriction in most vessels
3) Vasodilatation in arterioles of skeletal muscles and the heart
4) Vasoconstriction in arterioles of skeletal muscles and the heart
Answer: 2) Vasoconstriction in most vesselsExplanation: Norepinephrine acts on alpha-adrenergic receptors in the vascular smooth muscles, causing vasoconstriction in most blood vessels. This diverts blood flow to critical organs like the brain and muscles, preparing the body for physical exertion.
The first heart sound relates to
1. Closure of the A-V valves
2. Opening of the A-V valves
3. Excitation of the auricles
4. Closure of the aortic valve
Physiology
Answer: 2
The first heart sound relates to Opening of the A-V valves
In which sleep stage are delta waves most prominent?
1) Stage 1 NREM
2) Stage 2 NREM
3) Stage 3 NREM
4) REM sleep
Delta waves are high-amplitude, low-frequency brain waves that are most prominent during the deepest stage of NREM sleep, which is Stage 3 NREM, indicating deep sleep.
What is the primary effect of norepinephrine on the pupillary muscles during the fight-or-flight response?
1) Dilatation (mydriasis)
2) Constriction (miosis)
3) No effect on pupil size
4) It depends on the presence of other neurotransmitters
Answer: 1) Dilatation (mydriasis)Explanation: Norepinephrine acts on alpha-adrenergic receptors in the pupillary dilator muscles, leading to pupil dilation. This is a component of the sympathetic nervous system's response to stress, which also includes pupil dilatation mediated by epinephrine.
What is the role of intrinsic factor in vitamin B12 absorption?
1) It protects vitamin B12 from gastric digestion
2) It facilitates binding of vitamin B12 to intestinal receptors
3) It synthesizes vitamin B12 in the gastrointestinal tract
4) It increases the production of gastric acid
Physiology
Answer: 2
Intrinsic factor binds to vitamin B12 and protects it from digestion, allowing it to be absorbed in the ileum.