Question

Give two examples of a negative feedback loop and one example of a positive feedback loop within normal physiologic function. Describe each homeostatic mechanism using detailed descriptions. For each example predict the result at an organismal level if normal function was impaired at the molecular level.

Answer 1

Answer 2

Feed mechanisms play an important role in maintaining the homeostatic conditions of the body. They are of two types namely,

1. Positive feedback mechanism
2. Negative feedback mechanism

If the release of one hormone is further triggered by its release, then it is called a positive feedback mechanism or positive feedback loop.

Example of a positive feedback mechanism:

If the blood vessel is injured, the smooth muscle constricts producing a spasm, this response of smooth muscles decreases or stops the blood flow through it. This also activates the platelets, which clog and plug the damaged wall temporarily. The presence of platelets further triggers the release of clotting factors and promotes the clotting process to prevent blood loss. This is an example of a positive feedback regulation.

Negative feedback regulation:

1). Blood pressure regulation:

For example, if blood pressure is raised due to excess sympathetic stimulation, the parasympathetic system comes to get activated to regulate the raised blood pressure, otherwise, the small blood vessels collapse. This is an example of negative feedback regulation. Negative feedback regulation prevents the overcompensation operated to maintain the homeostasis, it is the most common feature of homeostatic regulation.

Example 2: Temperature regulation

Hypothalamus contains the temperature regulating center of the body. If the external body temperature is low, the control center compares the body temperature and external temperature and activate the mechanisms such as muscle contraction to maintain the normal body temperature. If the temperature becomes normal, the muscle contraction becomes normal to prevent an excessive rise in body temperature.