Homeostasis
Humans maintain a state of relative stability in their internal environment. This is referred to as homeostasis.
The word Homeostasis originates from two Greek words:
“Homeo-“meaning similar, and “-stasis” meaning standing still.
So, homeostasis literally means staying the same.
Homeostasis is a dynamic process that ensures conditions are stabilized above and below a set point.
Deviation from the set point sets in motion a series of events to restore this set point.
Restoration of set points is achieved by feedback systems.
Feedback Systems
A feedback system is a cycle of events in which the status of a body condition is monitored, evaluated, changed, re-monitored, and re-evaluated.
The monitored body condition is referred to as a controlled condition.
Examples of controlled conditions are body temperature, blood pressure, and blood glucose level.
A feedback system is composed of 3 main parts: a sensor, a control center, and an effector.
To understand a feedback system, let’s think about what happens when your blood pressure increases for some reason (may be you had too much salty food?)
In this scenario, your blood pressure is considered as the controlled condition. The increase in blood pressure is the deviation from the set point. Your body will activate a feedback system to restore that set point back to normal.
The increase in your blood pressure will be detected by sensors known as baroreceptors, present in some blood vessels.
The sensors will then send a signal to the control center, which in that case is the brain.
The brain in response will send a message to the effectors to reduce blood pressure. The effectors here are the heart and blood vessels. The heart will slow down and blood vessels will dilate in order to reduce your blood pressure back to its set point.
There are two types of feedback system:
- Negative feedback system.
- Positive feedback system.
A negative feedback system reverses a change in a controlled condition.
A positive feedback system reinforces a change in a controlled condition.
The example of blood pressure regulation discussed above is an example of a negative feedback system.
So, let’s discuss an example of a positive feedback system.
The most common example of a positive feedback system is normal childbirth.
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