Question

Which of the following is an example of a negative feedback?

• A. Sucking reflex
• B. Uterine contractions during labour
• C. Secretion of CRH in response to ACTH
• D. Hair erection due to low body temperature

Answer 1

The correct option is C Secretion of CRH in response to ACTH

One distinctive feature of hormones whose secretion is regulated through the hypothalamus and pituitary is that they regulate their own secretion through negative feedback inhibition. CRH (corticotropin releasing hormone) and ACTH (adrenocorticotropic hormone). Less tropic hormone secretion leads to less stimulation of cortisol secretion by cells of the zona fasciculata of the adrenal cortex. The usefulness of negative feedback inhibition is that it works to keep hormone levels within a particular appropriate physiological range. The reduced negative feedback inhibition means that more CRH and ACTH will be secreted. More ACTH will stimulate the remaining adrenal tissue to grow and to secrete more cortisol. This will have the effect of bringing cortisol back up towards its normal daily level of secretion.

So the correct option is ' secretion of CRH in response to ACTH'