communications and homeostasis Flashcards
stimulus
triggers a physical or behavioural change
response
behaviour caused in living organism which results from an external/internal stimulus
cell signalling
process by which a cell responds to substances outside cell
homeostasis
maintenance of internal environment around a set point despite environmental changes
negative feedback
mechanism that reverses change bringing system back to optimum
positive feedback
mechanism that increases change, taking the system further away from optimum
ectotherm
animal whose regulation of body temp depends on external sources (cold blooded)
endotherm
internally generated heat to maintain body temp (warm blooded)
vasodilation
widening of the blood vessels as a result of the relaxation of blood vessels in muscular walls
vasoconstriction
constriction/narrowing of blood vessels by small muscles in their walls
conduction
the transfer of sound waves, heat, nervous impulses of electricity
convection
the process of heat transfer by the bulk movement of molecules within a liquid/gas
radiation
energy released in form of particle or electromagnetic waves
hypothalamus
acts as body’s smart control coordinating centre
thermoregulatory centre
contains hypothalamus in brain, contains receptors sensitive to the temperature of blood
thermoreceptors
receptive portion if a sensory neurone, that codes absolute and relative changes in temperature
peripheral temp
temperature of the skin (influenced by environment)
peripheral temp receptors detect change in skin temp + alert hypothalamus as warning
activity level of ectotherm depends on…
external temp
if ectotherms are too cold..
- lie on warm surface
- move around to generate some heat
if ectotherms are too hot…
- move underground (burrow)
- decrease SA expose to sun
- increase rate + depth of breathing -> increase water evaporation
advantages of ectotherms
- decrease metabolic rate req.
- decrease food req.
- more food converted for growth
- can survive longer without food
disadvantages of ectotherms
- more vulnerable to fluctuations environment
- less active at colder temps
- more susceptible to predation if less active
- cannot exploit as many locations
why do lizards bask in the sun with their mouths open
gaping allows lizards to dissipate body heat as they don’t sweat so their body stays at opt temp.
suggest why aquatic ectotherms have relatively few problems maintaining a stable body temp
- water has high SHC 4.2KJ so stable temp and less fluctuations
