Homeostasis & Negative Feedback Control Loop

All the cells in the body are living in an internal environment, made up of extracellular fluid.
For well being of the cells, the constitution of the extracellular fluid needs to maintain constant. For example, glucose level, oxygen level, temperature, etc. need to be maintained within an optimal range that is suitable for the survival of the cells. There should not be too much increase or too much decrease.
All the cells, tissues, organs, and organ systems contribute to maintaining the internal environment at a constant level. This ongoing process of maintaining the internal environment at a constant level is called homeostasis.

Parameter deviates from the optimal range

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The deviation is sensed by a sensory system

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Compared with a set point

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A response is initiated

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Brings the parameter back to the set point

For example:

Increase in glucose level

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Sensed by pancreas

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Release of insulin*

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Insulin increases the uptake of glucose in liver and fat tissues

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Glucose level decreases i.e. comes back towards the optimal range

Intensifies initial change in a parameter.
For example:
- Activation of some clotting factors during coagulation cascade.
- Uterine contraction during childbirth.

When the hemostasis is disrupted the result can be disease or death.
For example, if insulin is not secreted in response to increased glucose, the body suffers various consequences of diabetes.

Next >>

In the next session, we will understand homeostasis with a fun metaphor of balancing a cycle.