Temperature control in endotherms Flashcards
what is an endotherm?
an organism that uses heat from metabolic reactions to maintain body temperature
what do endotherms have that enable them to control body temperature?
physiological and behavioural adaptations
how does the skin maintain body temperature?
if too hot:
- sweat glands secrete fluid onto the the skin surface as this evaporates it uses heat from the blood as the latent heat of vaporisation
- hairs and feathers lie flat to reduce insulation and allow greater heat loss
- vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away from the body
if too cold:
- less sweat is secreted so less evaporation means less heat is lost
- hairs and feathers stand erect which traps air which insulates the body
- vasoconstriction of arterioles and precapillary sphincters leading to skin surface, blood is directed away from the surface of the skin and less heat is lost
how does the gaseous exchange system maintain body temperature?
if too hot:
- some animal pant increasing evaporation of water from the surface of the lungs and airways, evaporation uses the heat from the blood as the latent heat of vaporisation
if too cold:
- less panting so less heat is lost
how does the liver maintain body temperature?
if too hot:
less respiration takes place so less heat is released
if too cold:
increased respiration in the liver cells means that more energy from food is converted to heat
how does the skeletal muscles maintain body temperature?
if too hot :
- fewer contractions meant that less heat is released
if too cold:
- spontaneous muscle contractions (shivering) release heat
how does the blood vessels maintain body temperature?
if too hot:
- dilation to direct blood to the extremities so that more heat can be lost
if too cold:
- constriction to limit blood flow to the extremities so that blood is not cooled too much- this can lead to frostbite in extreme conditions
what are the advantages of endothermy?
- maintain a fairly constant body temperature no matter the external temperature
- remain active even when external temperatures are low so can still catch prey and escape predators
- inhibit colder parts of the planet
what are the disadvantages of endothermy?
- use a large amount of energy intake on maintaining body temperature in the cold
- need more food
- use for growth a lower proportion of the energy and nutrients gained from the food
- may overheat in hot weather
what is the hypothalamus?
the part of the brain that coordinates homeostatic responses
what happens if temperature increases?
if blood becomes warmer than hypothalamic point the thermoregulatory centre in the hypothalamus which can either cause:
- skin blood vessels to dilates, capillaries become flushed with warm blood and the heat radiates from skin surface
- sweat glands are activated to secrete sweat which is vaporised by body heat helping to cool the body
body temperature decreases and blood temperature decreases and hypothalamus ‘shuts off’
what happens if temperature decreases?
blood is cooler than hypothalamic set point which activates the thermoregulatory centre in the hypothalamus which causes either:
- skin blood vessels to constrict and blood is diverted from skin capillaries and withdrawn to deeper tissues which minimises the overall heat loss from skin surface
- skeletal muscles are activated when more heat must be generated so shivering begins
body temperature increases and hypothalamus ‘shuts off’
what mechanism does the hypothalamus use?
negative feedback
what are peripheral receptors?
temperature receptors in the skin which monitors the temperature in the extremities which send signal to hypothalamus if environment is too hot or too cold and the brain can coordinate behavioural mechanisms such as moving out of the shade
