Answer:

Feedback mechanism is the mechanism of the body to maintain the levels of hormones in the body in the desired limits. An increase or decrease in the levels of the hormones triggers the feedback mechanism. 

The body has two types of feedback mechanisms, positive and negative feedback mechanism.

Example:

Negative feedback mechanism: 

Whenever there is a change in the normal state, the messages are sent to ‘increase’ secretions if there is a fall below normal or to ‘decrease’ secretions if there is a rise above normal to restore the normal body state. Such a mechanism is called a negative feedback mechanism.

The increase in the blood sugar level stimulates the secretion of insulin so that the sugar level is maintained. If the blood sugar level falls below normal, then it stimulates the secretion of glucagon. Glucagon stimulates the breakdown of glycogen to glucose, and thus, the normal sugar level is maintained.

Feedback Mechanism for Regulation of Hormonal Secretion
Feedback mechanisms play a crucial role in maintaining homeostasis in the body by regulating the secretion of hormones. One common example of a feedback mechanism in hormonal regulation is the hypothalamic-pituitary-adrenal (HPA) axis.

Example: Hypothalamic-Pituitary-Adrenal (HPA) Axis

1. Stimulus
- In response to stress or low levels of cortisol in the blood, the hypothalamus releases corticotropin-releasing hormone (CRH).

2. Pituitary Gland
- CRH stimulates the anterior pituitary gland to release adrenocorticotropic hormone (ACTH).

3. Adrenal Glands
- ACTH then signals the adrenal glands to produce and release cortisol, the stress hormone.

4. Feedback Mechanism
- When cortisol levels in the blood reach a certain threshold, they inhibit the release of CRH and ACTH through negative feedback.
- This inhibition prevents excessive production of cortisol and helps maintain homeostasis in the body.

5. Regulation
- The feedback loop ensures that cortisol levels are maintained within a narrow range, preventing overproduction or underproduction of the hormone.
- This regulation is essential for the body to respond appropriately to stress and other physiological challenges.
In conclusion, feedback mechanisms, such as the HPA axis, are crucial for regulating hormonal secretion in response to internal and external stimuli. These mechanisms help the body maintain balance and ensure optimal functioning of various physiological processes.