MDS PREP
Which hormone is primarily responsible for the conversion of 7-dehydrocholesterol to cholecalciferol in the skin?
1) Parathyroid hormone (PTH)
2) Vitamin D
3) Ultraviolet B (UV2) light
4) 25-hydroxyvitamin D3
Ultraviolet B (UVB) light is primarily responsible for the conversion of 7-dehydrocholesterol to cholecalciferol (vitamin D3) in the skin.
What is the function of the middle piece in a sperm cell?
1) It produces the enzymes needed for sperm maturation
2) It contains the mitochondria for energy production
3) It is responsible for the sperm's ability to penetrate the egg
4) It is involved in the process of fertilization
The middle piece of a sperm cell contains mitochondria, which provide the energy needed for sperm motility and movement towards the egg.
What hormone is secreted by the kidneys that stimulates red blood cell production?
1) Renin
2) Erythropoietin
3) Aldosterone
4) Cortisol
Erythropoietin is the hormone secreted by the kidneys that stimulates red blood cell production in response to low oxygen levels in the blood.
MCQ: The gastrocolic reflex is:
1) The contraction of the stomach triggered by the presence of food in the duodenum
2) The contraction of the small intestine triggered by the presence of food in the stomach
3) The contraction of the rectum triggered by the presence of food in the stomach
4) The contraction of the gallbladder triggered by the presence of food in the small intestine
The gastrocolic reflex is the contraction of the colon triggered by the presence of food in the stomach, facilitating bowel movements.
In which part of the nephron is bicarbonate primarily reabsorbed?
1) Loop of Henle
2) Distal convoluted tubule
3) Proximal convoluted tubule
4) Collecting duct
Bicarbonate is primarily reabsorbed in the proximal convoluted tubule, where it plays a crucial role in maintaining acid-base balance in the body.
MCQ: The glomerular filtration barrier consists of:
1) Endothelial cells
2) Basement membrane
3) Podocytes
4) All of the above
The glomerular filtration barrier consists of endothelial cells, basement membrane, and podocytes, all of which work together to filter blood in the kidneys.
What is the significance of the pre-to-post ganglionic fiber ratio in the sympathetic nervous system?
1) It indicates the speed of nerve impulse transmission.
2) It reflects the number of synapses involved in the pathway.
3) It is unrelated to the function of the sympathetic nervous system.
4) It indicates the level of sympathetic nervous system activity.
In the sympathetic nervous system, the pre-to-post ganglionic fiber ratio of 1:20 to 1:100 indicates that there are fewer postganglionic fibers than preganglionic fibers. This ratio suggests that each preganglionic neuron synapses with multiple postganglionic neurons, thereby amplifying the sympathetic response to a given input.
What is the role of calbindin in calcium absorption in the intestine?
1) It sequesters calcium in the intestinal lumen
2) It transports calcium across the brush border membrane
3) It binds calcium and prevents it from affecting epithelial signaling
4) It stimulates the release of calcium from the intestinal cells into the bloodstream
Physiology
Answer: 3
Calbindin sequesters calcium within the intestinal epithelial cells to prevent it from interfering with calcium-dependent signaling processes, thereby facilitating efficient calcium absorption without disrupting normal cellular function.