Homeostasis Flashcards
What processes affect body temperature?
- exothermic chemical reactions
- latent heat of evaporation
- radiation
- convection
- conduction
What are ectotherms?
- animals which use their surroundings to warm their bodies.
- core body temp. highly dependent on environment.
E.g fish, amphibians, all invertebrates
What are endotherms?
- rely on their metabolic processes to warm up and usually maintain a very stable core body temp regardless of environment - controlled by active processes.
- consequently have much higher metabolic demands.
E.g mammals and birds
What behavioural responses do ectotherms exhibit linked to radiation?
- basking: orientate themselves to receive maximum sunlight
- can even increase the SA of some parts of their bodies, e.g wings, to absorb more sunlight
What behavioural responses do ectotherms exhibit linked to conduction?
- press their bodies against the warm ground
- also get warmer as a result of metabolic reactions
- contract muscles e.g iguanas vibrate to increase metabolism and raise body temp
What behavioural responses do ectotherms exhibit to cool down?
- shelter in shade
- move into water or mud
- press body against cool stones or mud
- Minimise SA exposed to sun
- Minimise movement
What physiological responses to warming do ectotherms exhibit?
- darker colours to absorb more radiation in colder climates.
- alter HR/metabolic rate
- require less food
What are the different types of temperature receptors in endotherms?
- peripheral, in skin, surface temp
- hypothalamus, detect blood temp
What behavioural adaptations have endotherms developed?
- same as ectotherms
- hibernation and aestivation
How does vasodilation work to cool an endotherm down?
- arterioles near the surface of the skin dilate when the temp rises
- atriovenous shunt vessels constrict, forcing blood through the capillary networks close to the skin.
- flushed skin, increased radiation (or conduction if pressed against a cold surface)
How does sweating work to cool an endotherm down?
- rates of sweating increases core temp does.
- sweat evaporates, thermal energy transferred from skin to water, causing evaporation.
- panting causes water to evaporate out of breathing passages
How does reducing insulation work to cool an endotherm down?
- As body temp increases, erector pili muscles in the skin relax
- hair or feathers therefore lie flat to the skin, prevents layer of insulating air.
How does increasing insulation work to heat an endotherm up?
- erector pili muscles contract, hairs/feathers become erect
- layer of insulating air trapped
- use of fat deposits/layers
How does vasoconstriction work to heat an endotherm up?
- atriovenous shunts dilate.
- blood not diverted to capillary networks in skin
- less heat lost by radiation
How does decreased sweating work to heat an endotherm up?
- reduced cooling of skin by evaporation
How does shivering work to heat an endotherm up?
- rapid, involuntary contracting and relaxing of the large voluntary muscles in the body.
- energy released through this
How are polar bears adapted to their environment?
- hollow insulating hairs mean there is a permanent layer of insulating air.
- black skin to absorb radiation
- small ears
What two parts of the hypothalamus exist to regulate temp?
Heat gain centre and heat loss centre
How does the heat loss centre coordinate thermoregulation?
- temp of blood flowing through hypothalamus increases.
- sends impulses through autonomic motor neurones to effectors in skin and muscles
- responses triggered to lower core temp.
- blood cools down therefore impulses from heat loss centre stop.
How does the heat gain centre coordinate thermoregulation?
- temp of blood flowing through hypothalamus decreases
- sends impulses through the autonomic nervous system to effectors in skin and muscles
- triggers responses to increase core temp.
- blood warms up therefore impulses from heat gain centre stop
