Homeostasis is the maintenance of a constant internal environment within tolerable limitsHomeostasis involves the coordination of responses to a stimulus, with the body acting as a self-regulating mechanism. Homeostasis is coordinated by the nervous and endocrine system, carried out by negative feedback mechanism.

In a negative feedback mechanism, a stimulus or disturbance form the norm sets in motion a sequence of events which restore the system to its original optimal state (norm)When conditions are restored back to norm, a negative feedback is sent back to the control centre via receptors. This is to prevent further corrective actions.StimulusOn a warm day, blood and skin temperatures increase

ReceptorThis is detected by the temperature receptors in the skin,

Control CentreWhich sends a signal to the Hypothalamus in the brain,

Effectors (carry out corrective actions)Which triggers a series of corrective mechanisms by various body parts. Arterioles in the skin dilate, so that more blood flows to skin surface, so that more heat is lost through the skin by conduction, convection and radiation. Sweat glands become more active so that more sweat is produced. As more sweat evaporates from the surface of the skin, more latent heat of vaporization is removed. Metabolic rate also decreases so that less heat is produced within the body Rapid breathing occurs, to help remove heat.Fur-bearing animals: Hair erector muscles in skin relax so that there would be a thinner layer of still air trapped between the hairs so more heat can be lost.

NormIn these ways, the initial rise in temperature has been reversed/ Blood temperature decreases to the norm (optimum level)

Negative FeedbackA negative feedback is sent back to the hypothalamus to send signal to corrective mechanisms to inhibit further decrease in temperature.

StimulusOn a cold day, blood and skin temperatures decrease

ReceptorThis is detected by the temperature receptors in the skin,

Control CentreWhich sends a signal to the Hypothalamus in the brain,

Effectors (carry out corrective actions)Which triggers a series of corrective mechanisms by various body parts. Arterioles in the skin constrict, so that less blood flows to skin surface, so that less heat is lost through the skin by conduction, convection and radiation. Sweat glands become less active so that less sweat is produced. As less sweat evaporates from the surface of the skin, less latent heat of vaporization is lost. Metabolic rate also increases so that more heat is produced within the body Shivering occurs, which is a reflex uncoordinated contraction of the body muscles which increases heat productionFur-bearing animals: Fluff up their hairs by the contraction of hair erector muscles so that there would be a layer of still air trapped between the hairs become thicker so heat loss is slower as air is a poor conductor of heat.

NormIn these ways, the initial decrease in temperature has been reversed/ Blood temperature increases to the norm (optimum level)

Negative FeedbackA negative feedback is sent back to the hypothalamus to send signal to corrective mechanisms to inhibit further increase in temperature.