2.77b Thermoregulation

• Receptors-
• Transforms external energy into internal electrical impulses
• Controls body temperature
• Human enzymes:
• Woks best at 37-38 degrees
• Dangers of body temperature
• High: Heat stroke, dehydration
• Death if not treated
• Low: Hyperthermia
• Death if not treated
• The brain monitors the body's temperature
• When too cold/hot, the brain sends nerve impulses to the skin
• Has 3 ways of increasing or decreasing lost heat from the surface of the body
• Hair standing up - 
• Traps more warm air which reduces heat loss
• Less when lying flat
• Capillary network
• allows blood to move further away from skin
• Tiny muscles controls the hairs
• Sweat
• Glands under the skin secret when hot
• increases heat loss through evaporation
• When the body is back at normal temperature, the skin stops secreting
• Capillary network
• allows blood to move closer to the surface skin
• Blood vessels supplying blood to the skin can cause the skin to swell or dilate
• Hot Day-
• Vasodilation
• The blood vessels dilate (widen)
• Hairs are flat
• More heat is carried by the blood to the skin
• Can be lost to the air through sweat
• Cold Day-
• Vasoconstriction
• The blood vessels swell (shrink down)
• Hairs are raised
• Reduces heat loss
• Returns body temp back to normal