Temperature regulation is an examples of negative
feedback mechanism. The optimal body core temperature is about 36.8 ºC which is the homeostatic set point.
 This optimal temperature is closely
regulated due to factors like enzymes works best at certain temperatures. If
the temperature raises to 43ºC, it
may be fatal and cause death.  Whereas, if
the temperature falls below 32ºC, the
individual may go into coma and die. The changes in the temperature are
detected by nerve-endings in the skin and the hypothalamus of the brain. When
blood temperature raises above the optimal temperature, the heat-loss centre in
the hypothalamus is activated which then initiates an autonomic response. This
response triggers changes to the effectors like the blood vessels which
vasodilate and increase blood flow to the skin so that there is increase in
radiation, conduction and convection to lose heat. Subsequently, metabolic rate
and muscular activity are decreased to slow down further heat production. The
sweat glands, additional effectors, are activat

In negative feedback loop, has a
counteraction effect on its own influence. Therefore, the negative feedback
mechanism can increase or decrease the stimulus. If the level is high, the body
decreases it and if it is too low, it elevates it and thus it is known as
negative feedback. Homeostasis always tends to provide optimal internal
environment in which the body can function best.

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Another positive feedback mechanism is blood
clotting. When a blood vessel is damaged, platelets arrive to the site and
stick to the site of the injury. They release chemical signals that attract
more platelets to the site and accelerate the process of clotting. This
continues until the clot repairs the damaged vessel.

During labor, the oxytocin hormone is
released by the hypothalamus and released by posterior pituitary. The oxytocin
stimulates and intensifies the contraction of the uterus, forcing the head of
the baby into the cervix. Subsequently, more oxytocin is release when stretch
receptors that are in the cervix are activated. In turn, more oxytocin is
released causing more contractions and maintaining labor. This cycle continues
until the baby is born. Once the baby is born, the stretch receptors are
deactivated and since the stimulus is not present anymore, the release of
oxytocin is stopped ending the positive feedback mechanism.

In positive feedback mechanism, the output is
amplified to maintain homeostasis. They are designed to push levels out of
normal ranges. This is achieved by initiating a series of events, which
originates to amplify the effect of the stimulus. This mechanism can be useful
but are rarely used due to its ability to become uncontrollable. For instance,
child birth and blood clotting are paramount examples of the use of positive
feedback mechanism.


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