Parathyroid cells are inhibited from synthesizing and releasing 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) down regulation.
D) up regulation.
E) positive feedback.

Question

Quizplus · Accepted Answer

This process is an example of negative feedback, where the system responds to a stimulus (low calcium levels) by producing a response (synthesis and release of PTH) that opposes the stimulus (raising calcium levels), until the initial stimulus is removed and the response is inhibited (when calcium levels are high).

Parathyroid Cells Are Inhibited from Synthesizing and Releasing PTH When