Question | Answer |
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) |