Detecting Detecting Temperature ChangeTemperature ChangeDetecting Detecting Temperature ChangeTemperature Change• Internal (core) body

temperature is kept constant within a narrow range of about 37 - 38

• Changes to internal body temperature are detected by hot and cold receptors in the:– Skin – Hypothalamus– Spinal cord– Large veins– Parts of the digestive system

ReceptorsReceptors are made

up of sensory neurons

also called affector neurons

InternalInternal

ExternalExternal

Detecting Detecting Temperature ChangeTemperature ChangeDetecting Detecting Temperature ChangeTemperature Change• Changes in the external

temperature cause changes in the temperature of exposed skin

• These changes are detected by 2 different types of receptors located just under the skin:– Hot – these receptors detect heat by

increasing electrical impulses to the hypothalamus

– Cold – these send more electrical impulses when cold.

Detecting Detecting Temperature ChangeTemperature ChangeDetecting Detecting Temperature ChangeTemperature Change

Causes of Causes of temperature change temperature change Causes of Causes of temperature change temperature change

• To maintain a stable core temperature:

Heat Production = Heat Loss

•This is controlled by the hypothalamus

Heat Production Heat Production Heat Production Heat Production

• The body constantly produces heat through: – Cellular respiration

• The body is able to increase body temperature by:– Shivering– Movement– Increased metabolism– Raising the hair on skin surface

•Piloerection - trapping warm air close to the skin’s surface and reduces heat loss

– Reducing blood flow to skin •Vasoconstriction

}(all of these things increase the rate of cellular respiration)

Heat Loss Heat Loss Heat Loss Heat Loss • Heat is lost by the body through a

range of processes:– Radiation– Conduction– Convection– Evaporation

• The body is able to reduce body temperature by:– Increased sweating– Increased blood flow to skin’s surface

•Vasodilation– Decreased metabolism

}

Heat is transferred from warmer objects to

colder objects (a bit like diffusion)

(both of these occur due to the temperature difference (gradient) between our warm bodies and the air at the skin’s surface

When heat is lost in energy waves

When heat is lost to the air due to direct contact with skin

Even without sweating, water is lost from skin continually, causing a cooling effect

Movement of air which maintains the temperature gradient

Heat loss

Heat gain

Expired air

Urine faeces

sweat

Panting

Radiation

Conduction

Convection

behaviour

Radiation

Conduction

Convection

Metabolism

Vasodilation

Vasoconstriction

Vasodilation - capillaries increase in size to increase SA for heat to be lost (usually causes skin to appear pink/red - flushed)

Vasoconstriction - capillaries decrease in size in decrease SA for heat to be lost (usually causes skin to appear purple/blue)

Sweating Water evaporates. For liquid to change to a gas state heat is needed. As sweat evaporates it uses body heat to turn it into a gas.

Shivering

Uncontrolled muscle spasms. Muscle contraction requires energy (ATP) therefore cellular respiration will increase - a reaction that produces 60% heat.

Piloerection Hairs stand on end producing goose bumps trapping a layer of heat around the body.

Thyroxine Hormone that increases or decrease the metabolic rate. Pituitary gland stimulates the thyroid gland to increase/decrease production of thyroxine.

Insulation - fur, blubber feathers.

Decreasing SA - roll into ball sleeping together in nests.

Behavioural - take clothing off, seek shade jump around.

Normal Body Temperature 37°C

Normal Body Temperature 37°C

Body temperature increases

Body temperature decreases

•Sweating panting

•Vasodilation

•Decrease in Thyroxine

•decrease SA

•Burrow

•Shivering

•Vasoconstriction

•Increase in Thyroxine

•Increase SA

•Piloerection

TRH = thyrotropin releasing hormoneTSH = Thyroid stimulating hormone