MDS PREP
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 mechanism by which glucose is reabsorbed in the proximal tubules of the kidney?
1) Passive diffusion
2) Facilitated diffusion
3) Active transport
4) Osmosis
Glucose is reabsorbed in the proximal tubules of the kidney primarily through active transport mechanisms, utilizing sodium-glucose transporters.
What is the primary neurotransmitter involved in the sympathetic nervous system's response at the neuromuscular junction?
1) Acetylcholine
2) Norepinephrine
3) Epinephrine
4) Dopamine
Answer: 2) The primary neurotransmitter involved in the sympathetic nervous system's response at the neuromuscular junction is norepinephrine, which acts on alpha and beta-adrenergic receptors.
What is the effect of increased parathyroid hormone during pregnancy?
1) Decreased calcium ion liberation from maternal bones
2) Increased calcium ion absorption in the gut
3) Increased calcium ion excretion in the urine
4) Increased calcium ion mobilization from maternal bones for fetal use
Answer: 4) Increased parathyroid hormone during pregnancy stimulates liberation of calcium ions from maternal bones for the fetus's calcium needs.
Which of the following inhibits gastric acid secretion?
1) Low pH in the stomach
2) High pH in the duodenum
3) Secretion of gastrin
4) Both A and B
Physiology
Answer: 4
Gastric acid secretion is inhibited by acidification of the stomach and duodenum. Low pH (acidity) in the stomach inhibits gastrin release from G cells, while high pH in the duodenum also contributes to the negative feedback mechanism that reduces acid secretion.
What is the role of calmodulin in the contraction of smooth muscle cells?
1) It binds to calcium and initiates muscle contraction directly
2) It activates the sarcoplasmic reticulum to release calcium
3) It inhibits the release of calcium from the sarcoplasmic reticulum
4) It activates myosin kinase (MLCK) in the presence of calcium
Answer: 4) It activates myosin kinase (MLCK) in the presence of calciumExplanation: Calcium binds to calmodulin, forming a calcium-calmodulin complex. This complex then activates myosin kinase, which phosphorylates the myosin light chain, leading to the formation of cross-bridges between actin and myosin and initiating muscle contraction in smooth muscles.
What is the primary neurotransmitter released by the parasympathetic nervous system?
1) Norepinephrine
2) Acetylcholine
3) Serotonin
4) Dopamine
The parasympathetic nervous system primarily uses acetylcholine as its neurotransmitter, which acts on muscarinic receptors to produce its characteristic effects on various organs.
What is the primary function of the sympathetic nervous system during the fight-or-flight response?
1) Facilitation of digestive processes
2) Diverting blood flow to the gastrointestinal tract
3) Preparing the body for rest and digestion
4) Mobilizing energy and preparing the body for immediate action
Answer: 4) Mobilizing energy and preparing the body for immediate actionExplanation: The sympathetic nervous system is activated during the fight-or-flight response to mobilize energy and prepare the body for immediate action. It does this by increasing heart rate, dilating pupils, and diverting blood flow to muscles and the brain, among other effects.