Homeostasis :
Homeostasis HOMEOSTASIS is the maintenance of an organism’s internal environment within tolerable limits. Homeostasis is needed for maintaining:
Water concentration
Blood glucose concentration
Temperature Prevents cell damage Provides cell energy Provides optimum for enzyme activity Internal Conditions:
are not permanently fixed
change depending on the tissue
are in a state of dynamic equilibrium NEGATIVE FEEDBACK is when a change in conditions triggers mechanisms which reverse the change.
Negative Feedback :
Negative Feedback NEGATIVE FEEDBACK is when a change in conditions triggers mechanisms which reverse the change. RECEPTORS: detect a change in conditions out with normal limits
CONTROL CENTRE: determines the level at which an internal condition should be maintained.
MESSAGE: nervous or hormonal
EFFECTORS: organs which respond
CORRECTIVE RESPONSE: reverses the original change
Control of [Water] in Blood :
Control of [Water] in Blood Normal blood water Excess drink Raised blood [water] Osmoreceptors in Hypothalamus Less ADH released by pituary Kidney tubules less permeable High volume, dilute urine Excess sweating Lowered blood [water] Osmoreceptors in Hypothalamus More ADH released by pituary Kidney tubules more permeable Small volume, concentrated urine
Control of [Glucose] in Blood :
Control of [Glucose] in Blood Normal [glucose] in bloodstream Increase Receptor cells in pancreas More insulin Liver Excess glucose stored in glycogen Decrease Receptor cells in pancreas More glucogen Liver Glycogen converted to glucose Insulin: glucose stored in the liver
Glucagon: glucose released by the liver
Adrenalin: glucose released by liver Adrenaline:
Is produced as a result of stressful stimuli
Released by adrenal gland
Stimulates the breakdown of glycogen to glucose
Raises blood glucose levels
Control of body temperature :
Control of body temperature ECTOTHERM (‘cold blooded’): The animal is unable to control it’s own body temperature, it is regulated by the environment.
ENDOTHERM (‘warm blooded’): The animal controls it’s own body temperature by using energy. Normal body temperature Rise Thermoreceptors in Hypothalamus Messages to other effectors Decrease in metabolic rate Fall in body temperature Nerve impulses Skin Sweating ,Hairs low, vasolidation Fall Thermoreceptors in Hypothalamus Nerve impulses Skin no sweating ,Hairs raise, vasoconstriction Messages to other effectors Increase in metabolic rate & shivering Rise in body temperature