Thermoregulations In Endotherms Flashcards
what detects the change in surface temperatures of endotherms?
peripheral temperature receptors in the skin.
what detects the temperature of blood deep in the body?
temperature receptors in the hypothalamus.
what temperature is core body temperature?
37 degrees celsius.
how do endotherms regulate their core body temperature?
using internal exothermic metabolic activities and energy-requiring physiological responses.
what is the opposite of hibernation?
aestivation
what additional behaviroual responses do humans have?
- clothes to stay warm
- houses built and then heated or cooled.
what responses do endotherms have to cool down?
- vasodilation
- increased sweating
- reducing the insulating effect of hair or feathers.
how does vasodilation cool animals down?
- arterioles near the surface of the skin dilate when the temperature rises.
- the arteriovenous shunt vessels constrict.
- this forces blood through the capillary networks close to the surface of the skin.
- the skin flushes and cools as a result of increased radiation. if the skin is pressed against a cold surface, the cooling results from conduction.
how does sweating cool animals down?
- sweat spreads out across the surface of the skin.
- sweat evaporates from the surface of the skin.
- heat is lost and cools the blood below the surface.
how much sweat is lost from humans by evaporation on a normal day?
1 dm^3
why might animals pant?
loses heat through evaporation as the water evaporates.
how does reducing the effects of hairs on the body cool animals down?
- erector pili muscles in the skin relax when the temperature is high.
- hair or feathers lie flat to the skin. this avoids trapping air.
(little effect on humans)
what responses do endotherms have to warm up?
- vasoconstiction
- decreased sweating
- raising hairs
- shivering
how does vasoconstriction heat animals up?
- arterioles near the surface of the skin constrict.
- arteriovenous shunt vessels dilate, so little blood flows through the capillary networks close to the surface of the skin.
- warm blood is kept away from the surface of skin.
how does decreased sweating heat animals up?
- sweat production may stop entirely if temperatures are too hot.
- this reduces cooling by the evaporation of water from the surface of the skin.
how does raising hairs heat animals up?
- as body temp falls, erector pili muscles in the skin contract
- this pulls the hairs or feathers erect.
- this traps an insulating layer of air and reduces cooling through the skin.
how does shivering heat animals up?
- as body temperature falls, an animal may start to shiver.
- shivering is the rapid involuntary contracting and relaxing of the large voluntary muscles in the body.
- metabolic heat from exothermic reactions warm up the body.
how do polar bears demonstrate thermoregulation in extreme cold conditions?
- small ears and fur on their feet to insulate them from ice.
- hairs are hollow so permanently trap insulating layer of air.
- skin underneath is black so absorbs warming radiation
- thick layer of fat under the skin
what are the physiological responses of endotherms to changes in the core temperature a result of?
complex homeostatic mechanisms involving negative fedback control from the hypothalamus.
what are the two control centres for thermoregulation?
- the heat loss centre
- the heat gain centre
when is the heat loss centre activated?
when the temperature of the blood flowing through the hypothamalus increases.
how does the heat loss centre coordinate a response?
it sends impulses through autonomic motor neurones to effectors in the skin and muscles, triggering responses that act to lower the core temperature.
when is the heat gain centre activated?
when the temperature of the blood flowing through the hypothalamus decreases.
how does the heat gain centre coordinate a response?
it sends impulses through the autonomic nervous system to effectors in the skin and the muscles, triggering responses that raise the core temperature.
