THERMOREGULATION Control of body temperature 2016 Paul Billiet
THERMOREGULATION Control of body temperature © 2016 Paul Billiet ODWS
Core temperature n n n The core temperature of the human body is 37°C The core of the human body includes the organs of the thorax, abdomen and the head This is where the vital organs are located Their enzyme systems must operate in optimum conditions The periphery of the body can withstand some deviation from the core temperature © 2016 Paul Billiet ODWS
Heat loss and heat gain The body must balance its heat budget Heat is gained: n by conduction from warm air surrounding the body n by the body’s metabolic activity which generates heat e. g. when muscle move Heat is lost: n by conduction and radiation to cold air (or water) n by evaporation of sweat from the body surface (c. f. properties of water) n Humans can also affect their body temperature by changing their behaviour e. g. wearing different clothes, seeking shade © 2016 Paul Billiet ODWS
Maintaining the body temperature Keeping warm Staying cool Increased insulation, subcutaneous fat reduces the conduction of heat from the body Reduced sweating decreases evaporation Increase blood flow to skin, increases conduction and radiation of heat from the body Increased sweat secretion, increases evaporation Increased shivering, increases heat produced by muscle tissue 2 to 5 times Reduced activity © 2016 Paul Billiet ODWS
Core body temperature >37°C Thermoreceptors Hypothalamus nerves Muscles reduce activity Sweat glands increase secretion Muscles of skin arteriole walls relax Skin arteries dilate More blood to the skin. More radiation & conduction of heat More water covers the skin. More evaporation © 2016 Paul Billiet ODWS Less heat generated
NEGATIVE FEEDBACK Thermoreceptors Core body temperature >37°C Thermoreceptors Blood temperature Muscles of skin arteriole walls relax nerves Hypothalamus Sweat glands increase secretion Muscles reduce activity © 2016 Paul Billiet ODWS Body loses heat Return to 37°C
Core body temperature <37°C Thermoreceptors Hypothalamus nerves Muscles shivering © 2016 Paul Billiet ODWS nerves Sweat glands decrease secretion More heat generated Muscles of skin arteriole walls constrict Less water covers the skin. Less evaporation Skin arteries constrict Less blood to the skin. Less radiation & conduction of heat
NEGATIVE FEEDBACK Thermoreceptors nerves Core body temperature <37°C Thermoreceptors Muscles of skin arteriole walls constrict Sweat glands decrease secretion Hypothalamus nerves © 2016 Paul Billiet ODWS Blood temperature Muscles shivering Body loses less heat Body gains heat Return to 37°C
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