Question

Which of the following is an example of negative feedback?
A. Sucking reflex
B. Uterine contraction during labour
C. Secretion of CRH in response to ACTH
D. Hair erection due to low body temperature

Answer 1

Hint: Biological phenomenon where the final result of a system either promotes the system (positive) or inhibits the system (negative) is called feedback. It can be of two types:- Positive or negative. Feedback is a very important phenomenon of living beings as they allow organisms to maintain homeostasis. Homeostasis is the mechanism by which an organism maintains its internal body temperature in the changing external environment.

Complete Step by Step Answer:
Negative feedback occurs when the final output of a reaction results in decrease of that reaction. The response generated is opposite to the output of the reaction. Hormones secreted through the pituitary and hypothalamus gland regulate their functions and secretion through negative feedback. Negative feedback inhibition helps to secrete hormones at an appropriate physiological range. Adrenocorticotrophic hormone (ACTH) stimulates the secretion and synthesis of steroid hormones and cortisol from adrenal cortex. Less amount of ACTH will result in the production of less cortisol from the adrenal cortex. Reduced negative feedback means more CRH and ACTH will be secreted. More ACTH results in more cortisol back up towards its normal level of secretion.

Hence the correct option is C:- secretion of CRH in response to ACTH.

Note: More such examples of negative feedback are temperature regulation, blood pressure regulation, osmoregulation. Positive feedback results in more production means more contractions or more platelets. Negative feedback means less production means less heat, less pressure. Feedback is very important to maintain homeostasis and hence survival. Negative feedback is more involved in homeostasis but positive feedback is equally important.