Which of the following statements concerning vitamin D is false?
A. Vitamin D causes the kidney to excrete calcium.
B. Vitamin D is necessary for the uptake of calcium from the intestine.
C. Vitamin D begins its synthesis in the skin when the skin is exposed to ultraviolet light.
D. Vitamin D is important for calcium homeostasis.
E. Vitamin D is necessary for the formation of bones and teeth.
Answer: A
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Thymic hormones in the thymus are produced by ________ cells.
Fill in the blank(s) with the appropriate word(s).
Aldosterone increases reabsorption of the electrolyte __________________ while increasing secretion of the electrolyte ___________________.
Fill in the blank(s) with the appropriate word(s).
Where is the Humerus bone located?
What will be an ideal response?
A positive feedback loop occurs when the outcome of an event causes the event to continue occurring and amplifies its effects. Which of the following aspects of an action potential constitutes a positive feedback loop?
A. Opening of voltage-gated sodium channels causes voltage-gated potassium channels to open and release potassium to the extracellular environment, slowly counteracting sodium influx. B. The sodium-potassium pump exactly balances ion leaks by pumping three sodium and two potassium ions across the membrane. C. An initial flow of sodium ions into the neuron opens voltage-gated sodium channels, rapidly causing more sodium to enter. D. The threshold potential is around -55mV.