Homeostasis Flashcards
why do animals need to be able to respond to their external environment
in order to avoid harmful environments and survive
why do animals need to be able to respond to their internal environment
to make sure conditions are optima for their metabolism
why do plants need to be able to respond to their external environment
to avoid harmful environments and survive
what happens when a stimulus occurs in an organism
the receptor will detect the stimulus, effectors then bring about a response
give some examples of receptors
photoreceptors, glucose receptors
give some examples of effectors
muscle cells, cells found in pancreas
How do adjacent cells communicate, for example cells in the nervous system
by secreting chemicals called neurotransmitters which send signals to adjacent cells such as nerve or muscle cells
how to distant cells communicate with each other, for example the hormonal system
cels release chemicals (hormones) into the bloodstream and travel to distant cells
What on a cell allows the chemicals involved in cell signalling to be recognised
cell surface receptors
What is negative feedback and give an example of where this occurs
mechanism which restores levels to normal, blood glucose levels
What is positive feedback and give an example
mechanism which amplifies the change away from the normal level e.g blood clotting when more platelets are released
What is the difference between a receptor and an effector
receptors detect when a level has moved away from normal and this information is communicated via the nervous or hormonal system whereas effectors respond to counteract the change and bring the level back to normal
define homeostasis
the maintenance of a constant internal environment
what are ecotherms and give two examples
animals that can’t control their internal temperature so se behavioural methods instead e.g lizards and snakes
what are endotherms and give two examples
control their internal body temperature through homeostasis e.g elephants and humans
give some mechanisms of how to reduce body temperature
sweating- evaporation cools the skin
hairs lie flat- less air is trapped reducing insulation so heat can be lost more easily
vasodilation- arterioles near the skin surface dilate so more heat is lost from the skin by radiation
give some methods of increasing body temperature
shivering- muscles contract and more heat is generated from respiration
hormones- body releases adrenaline and thyroxine to increase metabolism
less sweat
hairs stand up- traps air so a layer of insulation is created
vasoconstriction- less blood flows through the capillaries so less heat is lost
what part of the brain helps maintain constant body temperature
hypothalamus
what is the name of the receptors which detect temperature
thermoreceptors
what type of thermoreceptors are located in the skin and detect external temperature
peripheral receptors
