2.77b Thermoregulation

Understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis.

receptors, transform external energy into internal electrical impulses. 

1. Controlling body temperature:

Human enzymes usually work best at 37-38 degres.

2. Extremes of body temp are dangerous: 
 - high temp can cause dehydration, heat stroke and death if untreated 
- low temp can cause hypothermia and death if untreated


3. Body's temp is monitored by the brain, when your too cold or too hot the brain sends nerve impulses to the skin, which has 3 ways in increasing or decreasing the heat los from the body's surfaces.

a) Hair standing up on the skin traps more warm air (reduce heat loss) and less if they are lying flat (increase heat loss). Tiny muscles is what controls the hairs to do so. The capillary network which allows blood to move further away from the skin.

b) When the body is too hot, glands under the skin secret sweat onto the surface of the skin to increase heat loss by evaporation. When body is back to normal temperature, the skin stops secreting sweat. And the capillary network allows blood to move closer to the suface of the skin.

c) Blood vessels supplying blood to the skin can swell or dilate.

On a hot day: the blood vessels dilate (widen) it is called vasodilation and hairs are flat. This means more heat is carried by the blood to the skin, where it can be lost to the air. (sweat)

On a cold day: the blood vessels shrink down (swell), this is called vasoconstriction and hairs are raised. This reduces heat loss through the skin ounce the body temp is back to normal again.