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lecture 3-3 homeostasis - In humans a specific part of the...

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In humans, a specific part of the brain, the hypothalamus Contains a group of nerve cells that function as a thermostat Thermostat in hypothalamus activates cooling mechanisms. Sweat glands secrete sweat that evaporates, cooling the body. Blood vessels in skin dilate: capillaries fill with warm blood; heat radiates from skin surface. Body temperature decreases; thermostat shuts off cooling mechanisms. Increased body temperature (such as when exercising or in hot surroundings) Homeostasis: Internal body temperature of approximately 36–38 ° C Body temperature increases; thermostat shuts off warming mechanisms. Decreased body temperature (such as when in cold surroundings) Blood vessels in skin constrict, diverting blood from skin to deeper tissues and reducing heat loss from skin surface. Skeletal muscles rapidly contract, causing shivering, which generates heat. Thermostat in hypothalamus activates warming mechanisms. Figure 40.21
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Thermoreceptors in hypothalamus [detect blood temperature] Thermoreceptors in skin [detect external temperature] Thermoregualtory center in hypothalamus smooth muscle in arterioles sweat glands erector pili muscles in skin skeletal muscles adrenal & thyroid glands vasodilation & constriction sweat skin hairs stand up shivering metabolic rate Thermoregualtory center in hypothalamus
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Thermoregulation - Modes of Heat Exchange
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