Quiz on Negative Feedback Mechanism

Questions

1. What is the physiological inhibition loop that controls the suppression and regulation of most endocrine hormones?

2. When TRH is released into the portal system it directs the thyrotrophs in the anterior pituitary to secrete ______________.

3. After negative feedback mechanism has occurred the hormone levels will tend to be _________.

4. When thyroxine is released in the blood and circulates to the hypothalamus and pituitary to suppress further ______ and ______ production.

5. The mechanism mainly depends on factors which maneuver the ________ and ______ of the hormones.

True or False

6. The high concentration of the hormone alone will trigger the negative feedback mechanism.

7. Negative feedback is generally termed as the response of the system in the same direction.

8. Negative feedback must be triggered by the effect and result of overproduction of the hormone.

9. Its major function is to bring the hormone levels back within the normal range.

10. Hypothalamic-pituitary-thyroidal axis is an example of an endocrine negative feedback loop.


Case Analysis

Discuss briefly what happens in the homeostatic negative feedback loop when a person’s thyroid hormone levels increases in the blood’s circulation.


Original Photo: by dube1111

Homeostatic Negative Feedback Control Mechanism

Negative Feedback Mechanism

- It’s the physiological inhibition loop controlling most of the endocrine hormones. In negative feedback, any change or variation from the normal range of function is divergent, or resisted. The change or variation in the controlled value signals the response that brings the function of organ back within the normal range. The mechanism primarily depends on factors which manipulate the metabolism and flow of the hormones. Therefore, the high concentration of the hormone alone will not trigger the negative feedback mechanism because it must be triggered by the effect and result of overproduction on the hormone.

A simple example of an endocrine feedback loop is the hypothalamic-pituitary-thyroidal axis. The hypothalamus produces the hypophysiotropic hormone, thyrotropin-releasing hormone (TRH), and releases it into the portal system where it directs the thyrotrophs in the anterior pituitary to secrete thyroid-stimulating hormone (TSH). TSH circulates to the thyroid and stimulates several steps in the thyroid that are critical in the production and release of thyroid hormone. Thyroxine is released in the blood and circulates to the hypothalamus and pituitary to suppress further TRH and TSH production.

References: Fundamentals of Clinical Chemistry by Bishop et al

Clinical Laboratory Diagnosis by John Bernard Henry et al (19th Edition)

Images: original is File:ACTH Negative Feedback.jpg