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Homeostasis maintaining internal conditions within narrow limits
Usually involves negative feedback,
Effectors are either muscles or glands, they bring about response
to a stimulus
Receptors detect stimuli e.g. thermo receptors
Negative Feedback departure from a set level is detected by
receptors. These send information to effectors which bring about a
return to the original value.
Thermo regulation - the regulation of body temperature
Endothermic animals warm blooded e.g. mammals, birds. These
produce lots of heat and retain what is required
Exothermic animals cold blooded e.g. reptiles, fish, and
amphibians. These produce less heat and retain very little of it.
Short-term heat production (1) shivering rapid contraction and
relaxation of muscle fibres. Major disadvantage uses lots of
energy (2) release of hormone adrenaline from adrenal glands,
this raises the metabolic rate of the individual.
Basal Metabolic Rate energy expended by a resting fasting person
in a room at a comfortable temperate.
Factors that effect metabolic rate:
Long-term heat production increased production of the hormone
thyroxine from the thyroid gland in the neck.
Radiation loss of heat via electromagnetic waves
when body is warmer than the surroundings.
Evaporation mainly via sweating
Conduction the loss of heat through contact with an
object/medium that is cooler than the body
Regulation of heat loss:
Vasoconstriction and vasodilatation alter blood flow
to the skin and hence regulate heat loss by changing
the diameter of the arterioles in the skin
Vasodilatation widening of arterioles, increase blood
Vasoconstriction narrowing of arterioles decrease
Erector pili muscle reduce heat loss the muscles contract causing
hair to stand upright. This traps a still layer of air close to the skin
and reduces heat loss.
Adipose tissue fat storage tissue