Thermoregulation

the maintenance of body temperature within a range that enables cells to function efficiently

Ectotherms depend on air temperature to regulate metabolic rates  “cold-blooded”  activity is regulated by environment  behavioural adaptations enable these organisms to overcome this limitation (i.e. reptiles sun themselves on rocks when body temp gets too low)

maintain a constant body temperature regardless of environment  “warm blooded”  a decrease in temperature causes increase in cellular respiration rate to produce heat

Response to heat:  sensors in brain detect a rise in body temperature, nerve message is coordinated with the hypothalamus(brain coordinating) center and a signal is sent to the sweat glands to initiate sweating  evaporation of perspiration(sweat) from skin causes cooling  nerve message also sent to blood vessels in skin causing vasodilation  vasodilation allows more blood flow to skin  blood loses heat to the skin, blood returning from skin to core of body cools internal organs

Response to cold:  thermoreceptors in skin send message to hypothalamus  hypothalamus sends message to organs and tissues to increase body temperature  nerves going to arterioles(small blood vessels that carry blood away from your heart) of skin cause smooth muscles to contract and arterioles to constrict (vasoconstriction)  limits blood flow and loss of heat from skin  nerve messages also carried to smooth muscle that surrounds hair follicles causing hair to stand on end, erect hair traps warm, still air next to skin surface reducing heat loss  hypothalamus also sends nerve messages that initiate shivering, shivering is rhythmic contractions of skeletal muscle which generate, heat production by increasing metabolism