Chapte r 10 – Temperature change
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Transcript of Chapte r 10 – Temperature change
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.