Parathyroid cells are inhibited from synthesizing and releasing parathyroid hormone (PTH) when circulating calcium levels are high.When calcium levels fall, the inhibition is removed, PTH is synthesized and released, and calcium levels rise in the blood until the parathyroid cells are once again inhibited.This process is an example of
A) negative feedback.
B) induction.
C) downregulation.
D) upregulation.
E) positive feedback.

Question

Quizplus · Accepted Answer

The process described is an example of negative feedback, where the response opposes the stimulus. In this case, the stimulus is low calcium levels and the response is the release of PTH to increase calcium levels, until the stimulus (low calcium levels) is removed and the response (PTH release) is inhibited.

Parathyroid Cells Are Inhibited from Synthesizing and Releasing Parathyroid Hormone