CHAPTER 10 – TEMPERATURE CHANGE

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Hormones – chemical regulators Endocrine system

Produces hormones

Endocrine glands Transported via

bloodstream, slower than nervous system signals

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Two receptors that detect temp change

Hot/Cold = detect-> increase rate of discharge of electrical info along ______ neurons.

Impulses -> hypothamalus

Temp receptors all over the body. Even in H.

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An example of homeostasis Mammals need more energy – compare

snake diet to human diet

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Heat in the form of infra-red heat rays that radiates from the body

in all directions

Water evaporates from the lung and skin surface. Heat is

required for this to occur.

Conduction from direct contact

Conduction into air occurs when the

temperature of the air is less than that of the body. Heat loss this

way stops if the temperature outside

is greater.

If the air around the body is moving then convection carries heat away from the

body causing greater heat loss

The erection of hair or fur results in a layer of air being trapped that acts as an insulation

layer between the skin and the external

environment.

Sympathetic motor neurons bring impulses from the hypothalamus to the muscle at the base of each hair causing them to contract and the hair to become

erect

Neurons in the hypothalamus send the impulses via the sympathetic nervous system to the peripheral blood

vessels in the skin

The impulses causes arterioles to constrict, reducing the surface area across which heat can be lost and reduces

the amount of blood flow close to the skin.

The alternate contraction and relaxation of small muscle groups. The hypothalamus activates somatic

motor neurons that controls muscles in the upper limbs and body trunk. All the energy of a muscle

contraction is converted to heat energy.

This can’t be kept up for long due to muscle tissue losing energy reserves.

Heat Sources

Ectothermic• Depend on

external sources to generate heat

Poikilothermic• Temperatur

e fluctuates with environment

Endothermic• Have

inbuilt source of body heat energy

Homeothermic• Organisms

that keep their body temperature stable

Surviving the Heat – structural, behavioural or physiological adaptations

Spinifex hopping mouse Behavioural

Avoiding the sun, being noctural

Physiological Specialized kidneys to

absorb water Concentrated urine

Structural Being smaller – release

more heat

Snake Behavioural

Basking in the sun Flattened body to

increase surface area to volume

Physiological Increase of blood

flow to skin to warm blood faster

Surviving the Cold Antifreeze – glycerol, amino acids, proteins

Keep their body liquids from freezing Migration – birds Burrowing – frogs and toads Mammals – insulating layers Bears?

Surviving in Water Aquatic Mammals such as elephant seals, whales

Higher concentration of red blood cells to increase oxygen carrying capacity

Insulating layer of fat. Up to 50cm thick

Counter-current exchange system• Fine network of vasular tissue

within fins, tails, outer appendages

• Outer vessels constrict when cold

• Outgoing artery is paired with incoming vein.

• Warmed blood from artery heats up cold blood from vein

• Appendages are usually small, to reduce SA.V ratio.