Human Biology 12 Temperature regulation

Metabolism and temperature Metabolism refers to all reactions occurring in the body Metabolic rate refers to the amount or speed of reactions in the body. It can be measured by measuring temperature, rate of oxygen consumption or rate of carbon dioxide production Reactions produce waste heat. The more reactions that occur, the greater the temperature Reactions rely on enzymes

Enzyme activity and temperature Enzyme activity Temperature

Metabolic rate and temperature As temperature increases, metabolic rate increases As metabolic rate increases, temperature increases

Heat production Heat can be produced by: Metabolism eg respiration Movement Voluntary eg exercise Involuntary eg shivering

Heat loss or gain Occurs from body surfaces Uses the processes of: Radiation Conduction Convection Evaporation

Radiation Loss without contact Most important in terrestrial organisms. Can be increased by Increasing surface area exposure eg basking, big ears, vasodilation, bare skin/reduced fur Can be decreased by Decreasing surface area exposure eg huddling, small ears, vasoconstriction, fur or feathers

Conduction Loss by contact Most important in aquatic organisms Can be increased by Increasing surface area exposure eg larger extremities, reduced fur, reducing insulation Can be decreased by Decreasing surface area exposure eg smaller extremities, increased fur, increased insulation (eg blubber)

Convection Loss by air movements Most important in land animals Can be increased by Increasing surface area exposure to wind eg sprawling, decreased fur Can be decreased by Decreasing surface area exposure to wind eg huddling, fluffing feathers, increased fur

Evaporation Loss of heat due to liquid turning to gas Most important in terrestrial organisms Can be increased by sweating, panting or wetting skin or fur Can be decreased by reducing sweating or panting, keeping surface dry or covered with thick fur or feathers

Control of body temperature Control of heat production Increasing or decreasing metabolic activity or movement (shivering or exercise) Control of heat loss Increasing or decreasing loss of heat from external or respiratory surfaces

An example of negative feedback Stimulus Negative feedbackReceptor ResponseModulator Effector Heat Thermoreceptors Hypothalamus in brain Sweat glands Increased sweating Cool down

An example of negative feedback Stimulus Negative feedbackReceptor ResponseModulator Effector Thermoreceptors Hypothalamus in brain Cold Muscles Shivering Warm up

Structural adaptations Bare skin or reduced fur Endomorphic body shape Counter current exchange Ectomorphic body shape

Physiological adaptations Sweating Increased breathing rate Increased heart rate Vasodilation Vasoconstriction Hunching Shivering

Behavioural adaptations Use a fan Immersing in cold water Seeking shade Resting during heat Reduce clothes Hot bath Use a heater Add clothes