The fat-soluble vitamin required for the formation and maintenance of cell membranes is ________.
A. vitamin B6
B. vitamin E
C. vitamin D
D. vitamin A
Answer: B
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Sensory receptors
A. send signals from the brain to muscles. B. act as an intermediate within the CNS between the ascending and descending tracts. C. work with muscles to generate motion. D. detect changes in and outside the body.
What mechanism causes the voltage-gated Na+ channels to close during an action potential?
A) The activation gate is voltage sensitive and closes close to the equilibrium potential for Na+. B) The activation gate is sensitive to K+ and closes when its intracellular concentrations drop. C) The inactivation gate has a time-dependent closure. D) The inactivation gate is voltage sensitive and closes close to the equilibrium potential for Na+.
The juxtaglomerular apparatus
a. is a combination of specialized tubular and vascular cells at a point where the beginning of the distal tubule comes into intimate contact with the afferent and efferent arterioles of the same nephron. b. secretes aldosterone. c. secretes renin. d. both (a) and (b) above. e. both (a) and (c) above.
Parathyroid hormone (PTH)
A. inhibits reabsorption of both calcium and phosphate. B. stimulates reabsorption of calcium but inhibits phosphate reabsorption. C. stimulates reabsorption of both calcium and phosphate. D. inhibits reabsorption of calcium but stimulates phosphate reabsorption.