Thermoregulation - Anatomy & Physiology
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Thermoregulation
Thermoregulation is the ability of an endothermic organism to maintain a relatively constant body temperature despite fluctuations in temperature of the external environment. This is a vital part of homeostasis.
- Homeotherm/Endotherm: an organism with an internal temperature which remains relatively constant despite external temperature fluctuations.
- Poikilotherm/Ectotherm: an organism having a body temperature which fluctuates with the external environment - eg Fish, Reptile.
Mechanism of Action
The thermoregulatory mechanism consists of:
- Sensory Component: neurones that possess nerve endings with thermoreceptors continuously monitor body temperature and transmit it to the integrating centre. These neurons may be within the skin or internal organs.
- Integrating Centre: the Hypothalamus is the control centre in the brain which compares the temperature information with an Internal Reference or Set point.
- Motor Component: neurons which send signals to alter the internal temperature - altering heat production or heat loss.
- These command signals may travel via the somatic motor system and affect heat production in skeletal muscle.
- These command signals may travel via the Sympathetic Nerve Fibres and change
- Blood Flow to the Skin
- Sweat Gland Activity
- Activity of the smooth muscles which regulate fur/plumage thickness
Adaptation to Heat
- Sweating - causes heat loss via evaporation.
- Reduction of the resistance of cutaneous arterioles = Vasodilation. This allows more heat from the circulation to be transferred to the air.
- Hairs on the skin lie flat - the arrector pili muscle attached to the proximal end of each hair follicle relax to minimise heat being trapped by the hairs.
Adaptation to Cold
- Sweating Stops
- Cutaneous arteries constrict - Vasoconstriction. This minimises heat loss from the blood to the body surface.
- Hairs on the skin are raised involuntarily by the arrector pili