QS Study

Positive feedback sometimes can be useful

The feedback mechanism, which is positive to the initial stimulus, is called positive feedback mechanism. This mechanism causes destabilizing effects in the body, so does not result in homeostasis. It is mainly responsible for amplification of the changes caused by the stimulus.

In rare instances, the body has learned to use positive feedback to its advantage such as-

Blood coagulation

When a blood vessel is ruptured and a clot begins to form, multiple enzymes called clotting factors are activated within the clot itself. Some of these enzymes activate the other inactivated enzymes and causing still more clots.


When uterine contractions become strong enough for the baby’s head to begin pushing through the cervix and stretch through the cervix, the stretch of the cervix, sends signals through the uterine muscle back to the body of the uterus, causing even more powerful contractions. Thus the uterine contractions stretch the cervix and cervical stretch causes more contractions. When this process becomes powerful enough the baby is born.

Generation of Nerve Impulse

Stimulation of nerve fiver causes slight leakage of Na+ through Na-channels in the nerve membrane to the interior of the fiber. Then Na+ entering the fiber change membrane potential, which in turn causes more opening of channels, more change of potential, still more opening of channels and so forth. Thus from a slight beginning, there is an explosion of Na+ leakage that creates nerve action potential. This action potential, in turn, excites the nerve fiber still further along the length. This process goes on until nerve signal goes all the way to all ends of the nerve fiber.