What is homeostasis| Its Mechanism, Positive & Negative Feed Backs
Homeostasis is “the maintenance of nearly constant conditions in the internal environment of a biological system.”
It is a dynamic and ever-changing process which tries to keep the body under normal levels at all the possible conditions.
The examples of homeostasis in our body include maintenance of constant ion concentration by kidneys and constant oxygen levels by the respiratory system.
Since a living body is subjected to many external and internal stresses, the homeostasis will keep the body at normal.
It does so by trying to correct a small change in the range of regular physiological conditions.
Mechanism of homeostasis:
Homeostasis is regulated by control systems which detect any changes in physiology and respond accordingly. The control system has parts like
a) Receptors / Detectors
b) Control center
Receptors are the ones which first detect the change in homeostasis and send the signal to control center.
Examples of effectors: Baroreceptors which detect the changes in B.P.
This is also called as the regulating center.
The control center estimates within which limits the changes have to be maintained, i.e., the variable factor. It receives the input from a sensor or detector. Once it determines the needed change, it sends a response to the effector.
The control center provides nervous stimuli or hormonal stimuli to bring desired homeostatic change.
Effectors carry out the signal provided by the control center and induce the desired changes in body physiology.
This is a constant process and requires readjustment of many physiological variables.
Types of homeostatic mechanisms
Though the homeostasis is controlled by the control center, the actual mechanism to do so is by either of the two methods like.
1. Negative feedback mechanism:
A feedback mechanism is one where a system’s response is altered based on the input it receives. The negative feedback mechanism is an inhibitory function. Here, the effector response decreases the effect of the original stimulus to bring back the homeostasis.
A negative feedback mechanism controls body temperature. It prevents the body temperature from getting too high or too low.
When the temperature is high, the system is inhibited to prevent a further rise in temperature. The stimulation of skeletal muscles, constriction of blood vessels in the skin is inhibited. This leads to lowering of body temperature.
If the temperature is low, the system is stimulated to enhance temperature rise. The temperature regulating center in the hypothalamus of the brain is activated. This leads to stimulation of skeletal muscles to produce more heat. Further, the peripheral blood vessels get constrict to minimize heat loss to the surroundings.
2. Positive feedback mechanism
This is an amplifier type of function. Here the stimulation progressively increases the response. As long as the stimulation is present, the response is also amplified.
This type of mechanism is seen in few systems like the blood clotting and the uterus contraction at the time of delivery.
More on Homeostasis:
Homeostasis of blood pressure: Normal blood pressure in humans is 120/80mmHg. If one is anxious or even irritated, his blood pressure tends to rise to 140/90. Again when he cools down, it returns to normal. Similarly, many other body organs like heart, lungs also increase in their function.
This rise is meant to adopt the body to the excess demand like more oxygen, energy to cope up the situation.
This shift in balance is quite normal and is within a few points. If it goes beyond, mostly it leads to disorders and even death based on the intensity and duration of deviation from homeostatic range.
Body systems like the nervous system, endocrine system are involved in the maintenance of homeostasis. This is done through nerve stimulation or changes in hormonal levels.
Other examples of correction of homeostasis are
- Sweating when the body temperature rises due to heat in summer.
- Gushing and intense breathing to give excess oxygen while running or jogging.
In the above conditions, the body tries to keep the system normal. In conditions of failure to keep up the body temperature within limits, the condition results to sunstroke. So the ability of the body to maintain homeostasis is essential to keep the body healthy.