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what is homeostasis? control of an organisms internal environment in order to maintain optimum conditions
what do enzymes require to function? suitable pH, suitable temperature, aqueous environment free from toxins and inhibitors
what is stimulus? environmental change
what is response? organism changes its physiology or behavior
examples of external fluctuations? weather, climate, pollution, altitude
examples of internal fluctuations? blood glucose, water, hormones
examples of homeostatic mechanisms? sweat, shivering, vasoconstriction and vasodilation
what is the standard pathway response? stimulus - sensors - communication system - effectors - response
what is negative feedback? the sensors find that optimum conditions have been reached and sends a signal to the control center, which then switches off the effector
what is positive feedback? the response increases the change away from optimum conditions and does not lead to optimum conditions
example of negative feedback? stimulus; temperature increase - sensors; thermoreceptors in the skin - communication system; thermoregulatory centre in hypothamalus - effectors; blood vessels and sweat glands - response; blood vessels vasodilate, sweat is released
example of positive feedback? childbirth, oxytocin is released to cause contractions, taking the mother away from optimum conditions until baby is born
what is conduction? heat transfer between two objects, e.g. the ground and base of foot
what is convection? heat transfer between an organism and air current
what is radiation? heat released as a wave from a hot object?
what is evaporation? heat lost when water changes from a liquid to a gas (e.g. sweat)
what is an endotherm? an animal that is capable of or dependent on the internal generation of heat
what is an ectotherm? an animal that relies on the sun for heat and isn't capable of internally generating heat
advantages of being an endotherm? able to live in cold areas, do not rely on sun and therefore aren't lethargic at night
disadvantages of being an endotherm? consume lots of energy maintaining body temperature
what is vasoconstriction? blood capillaries constrict to prevent blood flowing near the skins surface to prevent heat loss through radiation, blood flows deep down
what is vasodilation? blood capillaries dilate to allow blood to flow close to skin surface to allow heat to be lost through radiation
what is BMR? the basic minimum amount of energy required to sustain the body's vital functions
what hormones affect BMR? stress hormones released from adrenaline gland and thyroxine from the thyroid gland
what causes fluctuations in body temperature? external environment fluctuations
what happens to enzymes if body temperature increases or decreases too much? denature (die)
Created by: deannarosee