Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892



Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

Discuss Concepts Positive feedback mechanisms are rare in animals compared with negative feedback mechanisms. Why do you think this is so?

Summary Introduction

To review:

The positive feedback mechanisms that are rare in animals as compared to the negative feedback mechanisms.


The meachnism of the body, wherein the input process is regulated in response to the output of the process, is referred to as feedback mechanism. It can either be positive or negative. In a positive feedback mechanism, the feedback gives a positive signal that accelerates the response whereas in a negative feedback mechanism, the feedback gives a negative signal that reduces the response.


The positive and negative feedback mechanisms can be explained by taking examples:

Positive feedback mechanism: Human childbirth is an example of a positive feedback mechanism when the fetus has grown fully, there is a contraction of the uterus that pushes the head of the fetus against the cervix. This causes the opening of the uterus, which further causes stretching of the cervix. The sensory neurons detect this stretching and give a positive signal to the hypothalamus to release the oxytocin through pituitary gland. Oxytocin causes further uterine contractions and accelerates squeezing pressure on the fetus to further stretch the cervix. This causes the release of more oxytocin and as a resultant accelerates uterine contraction until the fetus is pushed out.

Negative feedback mechanism: Homeostasis is controlled by a negative feedback mechanism...

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