Homeostasis

Stimulus

Any change in the environment that causes a response

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Response

A change in behaviour or physiology as a result of a chnage in the environment

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Good communication system

covers the whole body, enables specific communication, enables rapid communication, enables cells to communicate with each other, short-term and long-term responses.

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2 major communication systems

Neuronal and Hormonal

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Homeostasis

Maintaining a constant internal environmnet, despite changes in the external and internal factors

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Conditions that must be kept constant

Body temperature, blood pressure, blood salt concentration, blood glucose concentration, carbon dioxide concentration, water potential of the blood

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Negative feedback

The reversal of a change in the internal environment to return to a steady state or optimum condition

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stimulus-resonse pathway

stimulus, receptor, communication pathway, effector, response

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negative feedback example

body temperature

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positive feedback

process that increases any change deteted by the receptors

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positive feedback examples

Hypothermia and child birth

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Ectotherm

An organism that relies on external sources of heat to maintain body temperature

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Endotherm

An organism that uses heat from metabolic reactions to maintain body temperature

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Ectotherm examples

Snake, Locust, Lizard, Horned Lizard

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Snake behavioural adaption and benefit

Basks in the sun - absorbs heat directly from the sun

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Locust behavioural adaption and benefit

Sit side-on to the sun, climb to the top of a plant, increase rate and depth of beathing when hot - Increases SA, absorb more heat from the sun or to get away from the soil which radiates heat, more water evaporates from tracheal system to cool them

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Lizard behavioural adaption and benefit

burrows between rocks - underground burrow has a more stable temperature

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Horned Lizard behavioural adaption and benefit

Expands or contracts ribcage - to increase/decrease SA so more/less heat can be absorbed

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Ectotherm advantages

less food used in respiration, don't need to find as much food, more energy from food can be used for growth.

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Ectotherm disadvantages

less active in colder temperatures, increased predation risk, must store enough food for winter

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Hypothalamus

The part of the brain that coordinates homeostatic responses

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Exergonic reaction

release energy in the form of heat

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Endotherm organ examples

Skin, gaseous exchange system, liver, skeletal muscles, blood vessels

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Endotherm animal examples

Shark, shrew, sparrow, gorrila, human

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Skin response if body is too hot

sweat which evaporates using heat from the blood as the latent heat of vaporisation. Hairs and feathers lay flat to reduce insulation and to allow for convection and radiation. Vasodilation.

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Gaseous exchange system response if body is too hot

Some animals pant, which increases evaporation of water from the surface of the lungs and airways, using the blood as the latent heat of vaporisation

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Liver response if body is too hot

Less respiration takes place, so less heat is released. Rate of metabolism can be increased or decreased.

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Skeletal muscles response if body is too hot

Fewer spontaneous muscle contractions, so less heat is released

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Blood vessels response if body is too hot

Dilation to direct blood to the extremities, s that more heat can be lost

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Endotherm advantages

constant body temperature, despite the external temperature, active even in colder temperatures, can inhabit colder parts of the planet

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Endotherm disadvantages

Energy intake used to maintain body temperature, more food needed, less food energy used for growth

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Vasodilation

precapillary sphincters open. The blood moves to the surface of the skin, resulting in heat loss via radiation.

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Vasoconstriction

precapillary sphincters close, so there is less blood at the surface of the skin, resulting in less heat loss via radiation

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What do endotherms use to monitor their blood temperature?

The thermoregulatory centre in the hypothalamus

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Peripheral tempertaure receptors in the skin

monitor the temperature in the extremities and feed information to the thermoregulatory centre in the hypothalamus

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mesotherm

a type of animal with a thermoregulatory strategy immediate to ectotherms and endotherms.

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Homeostasis

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