communication and homeostais Flashcards
why do multicellular organisms need communication systems
so that animals and plants can respond to their internal and external environments, so thar conditions are kept optimum for their metabolism and organs function normally without damage
to coordinate activites between different organs
how is cell signalling done over large distances?
by hormones
what is a receptor?
detects stimuli, they are specific and dectect only 1 stimulus
what is an effector?
bring about a response to a stimulus
muscle or gland
what is homeostasis?
control systems to keep internal environment within certain limits
vital for the normal functioning of cells and to prevent their damage
uses negative feedback
describe negative feedback
receptors detect a change in levels when too high or too low
information is communicated by hormonal or nueronal system to the effectors
the effectors respond to counteract the change
what is positive feedback?
amplifys a change from the normal level
effectors respond in a way to increase the level away from the normal usually used to rapidly activate something
not used in homeostasis
give an example of positive feedback
blood clotting
platelets activated and then produce a chemical that activates more platelets and forms a clot
what are endotherms?
organisms that regulate their own temperature, usually maintaining a very stable core temperature regardless of their environment
what are 3 ways in which endotherms reduce their temperature?
sweating- sweat glands produce more sweat
erector pili muscles relax so that hairs lie flat
vasodilation- of superficial arterioles
what are 5 ways in which endotherms increase their temperature?
shivering- muscles contract in spasms
sweat glands produce less sweat
erector pili muscles contract so hairs stand on end
vasoconstriction of superficial arterioles
what receptors detect temeprature change in endotherms?
thermoreceptors
- peripheral temperature receptors- surface temperature
- hypothalamus- temperaure of blood deep in body
what happens when body temperature increases above normal in endotherms?
the heat loss centre in the hypothalamus detects change and stimulates vasodilation, sweating, relaxing of erector pili and decreased metabollic rate
what are exotherms?
use the surroundings to warm their bodies so their temeprature is heavily dependent on the environment
what do exotherms do when they need to cool down?
shelter from the sun
press against cold surfaces
orientate themselves so that the smallest surface area is exposed to the sun
