Communications and Homeostatsis

Communications and Homeostatsis

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  • Created by: harry
  • Created on: 02-01-12 18:53


Communications: All living organisms must detect and respomd to a change in their enviroment. Multicellular organisms: organise and communicate the response to chnage using nervous and endocrine (hormone) systems.

Cell signalling: Electrical: neurones?: nervous system, Chemical: hormones: the endocrine system.

Homeostatsis: maintanance of a internal enviroment, despite the external changes.

Negative feedbak: Brings about a reversal of any change. Ensures a optimun staedy state can be maintained. And is returned to the orginal set/ norm point.

Stimulus: any change in thye enviroment taht causes a response. Receptor: cell which detects a stimulus. Effector: brings a response eg: muscle/gland. Response: a change in behaviour or physiology as a result of a change in the enviroment.

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Thermoregulation: Endotherms

Endotherms: organisms which can control production and loss of heat to maintain their core body temperature.

Mammals, and birds have a constant temperature at 37c. Thermorecpetors detect a change in core body temperature. Hypothalamus of the brain detects and coordinates a physiological/ behavioural response. (negative feedback)


Shivering: hypothalamus sends nerve impulses to the skeletal muscles causes contractions, which generate MORE heat as increase in respiration. Heat transfered yto blood.

Release of adrenaline/ thyroxine: hormone increase the rate of respiration, energy released during respiration, is then lost as heat energy, and trandsferred into the blood.

Decrease heat loss via:

Vasocontriction: hypothalmus sends nerve impulses to the surface arterioles. Contracts to contrust the lumen, diverts blood away form the surface. Less heat lost via radiation

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Thermoregualtion continued:

Hairs on skin: Nerve impulese from the hypothalmus go to the erector muscles, attached to the hairs, the muscle contract, and so hairs rise trapping a layer of insulating air. Less heat lost via radiation.

Decrease in sweating: less heat loss via evapouration of sweat from the skin.

Behavioural response: incraesed into movement to generate heat in muscles; move into sunlight.


Vasodilation: hypothalamus sends nerve impules to the muscles of the surafce arteriolies, causing them to dilate, dirverting blood to the surface cappillaries, more heat lost via radiation.

Hairs on the skin: Nerve impulses from the hypothalmus to the erector pili muscles are inhibited. The muscles relax, causing hairs to lie flat and provide little insulation, therefore causing more heat lost via radi.

Sweating: Increase in sweating, Hypothalmus, send nerve impuleses to sweat gland, causes the release of sweat. The water in sweat evapourates. Latent heat of vaporisation. Panting:increases evaporation of water from lungs and tongue. Behavioural responses: animals: mud bathing, shade seeking.

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Endotherm and Ecotherm.

Ads of endotherm :): Maintain a constant internal enviroment temperature despite the external. Active in cold conditions. Able to inhabit colder area of the earth.

Dis of endotherm: High proportion of energy intake used to maintain body temperature. Higher food requirement. Less energy from food intake avalible for growth.

Ecotherm: organisms whihc relies on external source of heat, regulates body temp. Ecotherms: cant increase respiration rates: generates heat internally, so dont use internal energy sources to maintain their body temperature, they rely in increasing the exchange of heat with their enviroment. Ecotherms, change their behaviour or physiology to increase absorbance of heat from enviroment in cold decrease abs inhot.

Ads of being a ecotherm:) Use less food in respiration, require less food therefore can survive without eating for long periods. Energy from foods can be used for growth.

Dis of being ecotherms :( Less active in cooler temperatures therefore incraesed risk of predation. Inactive in winter therefore require a large energy stores to survive.

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