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Temperature regulation
HBS3A
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Homeostasis
Maintenance of constant internal environmentThis involves continually replacing substances as they are used up (eg glucose, oxygen) or continually removing substances as they build up (eg wastes)
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Negative feedback systems
• Stimulus
• Receptor
• Modulator
• Effector
• Response
• Negative feedback
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Negative feedback systems
• Stimulus change in conditions• Receptor detects the change• Modulator decides what to do about the
change• Effector part of the body that carries out
the response• Response change in activity• Negative feedback response alters the
stimulus in the opposite direction
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Metabolism and temperatureMetabolism refers to all reactions occurring in the
bodyMetabolic 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
temperatureReactions rely on enzymes
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Enzyme activity and temperature
Enzyme activity
Temperature
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Metabolic rate and temperature
As temperature increases, metabolic rate increases
As metabolic rate increases, temperature increases
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Body temperaturePoikilotherms have changing body
temperatures - the same as their environment
eg fish, amphibians, reptilesHomeotherms have constant body
temperatures regardless of the environment
eg birds, mammalsEctotherms control body temperature
by behavioureg fish, amphibians, reptilesEndotherms control body temperature
by internal mechanisms eg birds, mammals
Humans are endotherms and homeotherms
Environmental temperature
Bodytemperature
Metabolic rate
Environmental temperature
Poikilotherms
Endotherms
Homeotherms
Ectotherms
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Heat production
Heat can be produced by:• Metabolism eg
• Movement
Voluntary eg Involuntary eg
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Heat production
Heat can be produced by:• Metabolism eg respiration
• Movement
Voluntary eg exercise Involuntary eg shivering
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Heat loss or gain
Occurs from body surfaces
Uses the processes of:
• Radiation
• Conduction
• Convection
• Evaporation
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Radiation
Loss without contact
Can be increased by
Can be decreased by
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Radiation
Loss without contact
Can be increased by
Increasing surface area exposure eg basking, vasodilation, taking off clothes
Can be decreased by
Decreasing surface area exposure eg huddling, vasoconstriction, putting on clothes
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Conduction
Loss by contact
Can be increased by
Can be decreased by
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Conduction
Loss by contact
Can be increased byIncreasing surface area exposure eg swimming
Can be decreased byDecreasing surface area exposure eg increased
insulation (eg blubber)
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Convection
Loss by air movements
Can be increased by
Can be decreased by
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Convection
Loss by air movements
Can be increased by
Increasing surface area exposure to wind eg sprawling, taking off clothes, turning on fan
Can be decreased by
Decreasing surface area exposure to wind eg huddling, putting on clothes
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Evaporation
Loss of heat due to liquid turning to gas
Can be increased by
Can be decreased by
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Evaporation
Loss of heat due to liquid turning to gas
Can be increased by sweating, panting or wetting skin
Can be decreased by reducing sweating or panting, keeping surface dry or covered with clothing
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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
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Temperature regulation
Stimulus
Negative feedback Receptor
Response Modulator
Effector
Increased temperature
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Temperature regulation
Stimulus
Negative feedback Receptor
Response Modulator
Effector
Increased temperature
Thermoreceptors
Hypothalamus in brain
Sweat glands
Increased sweating
Cool down
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Temperature regulation 2
Stimulus
Negative feedback Receptor
Response Modulator
Effector
Cold
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Temperature regulation 2
Stimulus
Negative feedback Receptor
Response Modulator
Effector
Thermoreceptors
Hypothalamus in brain
Cold
Muscles
Shivering
Warm up
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Structural adaptations
Bare skin or reduced fur
Endomorphic body shape
Counter current exchange
Ectomorphic body shape
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Physiological adaptations
Sweating
Increased breathing rateIncreased heart rate
Vasodilation
Vasoconstriction
HunchingShivering
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Behavioural adaptations
Use a fan
Immersing in cold water
Seeking shadeResting during heatReduce clothes
Hot bath
Use a heater
Add clothes