MDS PREP
What is the primary function of vitamin D in the body?
1) Blood clotting
2) Bone formation and maintenance
3) Vision
4) Immune system function
Physiology
Answer: 2
Vitamin D is essential for the absorption of calcium and phosphorus from the diet, which are critical for bone formation and maintenance. It also plays roles in muscle function and immune system regulation, but its primary function is in the skeletal system.
Which of the following is the primary active transport mechanism for calcium absorption in the intestine?
1) Vitamin D dependent calcium binding protein (calbindin)
2) Sodium-calcium exchanger (NCX)
3) Calcium-dependent ATPase
4) All of the above
Physiology
Answer: 4
Calcium is absorbed mainly in the duodenum and jejunum by an active transport mechanism regulated by 1,25 (OH)2 D3 (calcitriol). It is transported across the brush border of intestinal epithelial cells via TRPV6 channels and binds to calbindin. The absorbed calcium is then delivered to the basolateral membrane by calbindin, and from there it is transported into the bloodstream by either the sodium-calcium exchanger (NCX) or calcium-dependent ATPase.
What is the primary function of the juxtaglomerular apparatus (JGA)?
1) Regulation of blood volume and blood pressure
2) Formation of urine
3) Secretion of renin
4) Concentration of urine
The primary function of the juxtaglomerular apparatus (JGA) is the secretion of renin, which regulates blood volume and blood pressure.
What is the primary function of the neck in a sperm cell?
1) It connects the head and tail of the sperm
2) It produces the sperm's energy for movement
3) It is responsible for the fertilization process
4) It contains the cell's genetic material
The primary function of the neck in a sperm cell is to connect the head and tail of the sperm, facilitating movement and energy transfer.
What is the primary neurotransmitter responsible for the contraction of the pupillary sphincter muscle?
1) Acetylcholine
2) Norepinephrine
3) Epinephrine
4) GABA
Answer: 1) AcetylcholineExplanation: The pupillary sphincter muscle is innervated by the parasympathetic nervous system, which uses acetylcholine as its primary neurotransmitter. Contraction of this muscle leads to pupil constriction, or miosis, which occurs in low-light conditions or when focusing on near objects.
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 function of the pineal gland in regulating circadian rhythms?
1) It produces melatonin in response to light exposure
2) It produces cortisol to maintain wakefulness
3) It regulates body temperature
4) It is not involved in circadian rhythms
The pineal gland produces melatonin in response to light exposure, helping to regulate circadian rhythms and sleep-wake cycles.
What is the primary mechanism by which acid secretion is regulated in the stomach?
1) By the pH of the stomach content
2) By the amount of food present
3) By the time of day
4) By the type of food consumed
The primary mechanism by which acid secretion is regulated in the stomach is by the pH of the stomach content, which influences gastric secretions.