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Homeostasis
| 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) |
Created by:
deannarosee