thermoregulation biology stage 3 chapter 15 pages 317-324
DESCRIPTION
Keywords Thermoregulation Ectotherms Endotherms Metabolic heat Heat exchange Insulation ◦ Brown fat Surface area-to- volume ratio Temperature gradient Physiological responses Piloerection Vasodilation Vasoconstriction Evaporating ◦ Sweating ◦ PantingTRANSCRIPT
ThermoregulationBiology Stage 3Chapter 15Pages 317-324
YouTube clip
Thermoregulation (Bozeman Science 5 min)
https://www.youtube.com/watch?v=TSUCdLkI474&feature=youtu.be
KeywordsThermoregulationEctothermsEndothermsMetabolic heatHeat exchangeInsulation
◦Brown fatSurface area-to-
volume ratioTemperature
gradient
Physiological responses
PiloerectionVasodilationVasoconstrictionEvaporating
◦Sweating◦Panting
EctothermsAll animals, other
than birds and mammals, are ectotherms (‘outside heat’)
They do not generate their own heat but have a body temperature the same as that of the environment, whether it is hot or cold
They are often inactive during winter because their cells function so slowly at low temperatures
Ectotherm Ectotherms do alter
their behaviour to vary their internal temperature
They lie in the sun to warm up or burrow underground to stay cool
Some animals (some fish & insects) use the heat produced by their metabolism or by muscular activity (metabolic heat) to maintain a body temperature higher than the environment
EndothermsEndotherms (birds &
mammals) generate and maintain their own body heat
Maintaining body heat is called thermoregulation
If the environment is colder, the internal temperature is maintained by increasing heat production and reducing heat loss
If the environment is warmer, the internal temperature is maintained by decreasing heat production and increasing heat loss
EndothermsThermoregulation
involves:1. controlling
metabolic heat production
2. regulating heat exchange with the environment
Controlling heat productionHeat production is
controlled through increasing or decreasing metabolic activities
Metabolic heat can be generated by:Increasing muscle
activity (shivering)Increasing cellular
activity (brown fat)Increasing rates of
cellular metabolism
The hypothalamus is the regulatory centre in the brain
It signals to increase or decrease metabolic activities
It also regulates physiological responses to maintain homeostasis
Heat sensors or thermoreceptors in the body relay information to the hypothalamus
Regulating heat exchangeThe rate of heat
exchange with the environment depends on:
1. Insulation2. Surface area-to-
volume ratio3. Temperature
gradient between the body and the environment
4. Adaptive behaviours
INSULATIONFur & feathers Trap layer of warm air next
to skin Fur and feathers only good
insulators when dry Piloerection – tiny muscles
cause hair to lift away from skin increasing the thickness of the trapped air layer
Layer of fat Brown fat – hibernating
animals Large amount of
mitochondria
Regulating heat exchangeSURFACE AREA-TO-VOLUME
RATIO Smaller animals have a
larger surface area-to-volume ratio than larger animals
They therefore require relatively more food to maintain a higher metabolic rate
ADAPTIVE BEHAVIOURS Endotherms can vary their
behaviour to maintain optimum body temperature
TEMPERATURE GRADIENTRegulation involves: Circulatory changes
◦ Vasodilation◦ Vasoconstriction
Counter-current arrangements of blood vessels
Loss of heat through evaporation◦ Sweating◦ Panting
Countercurrent heat exchange
Rising body temperature
Falling body temperature
Feedback systems Negative feedback systems
have a number of common features:
The stimulus is the change in the environment
The receptor detects the change
The modulator is a control centre responsible for processing information
The effector carries out a response counteracting the effect of the stimulus (or change in the environment)
Behavioural responses to change in external temperature
Sensory receptor
Eff ector
External temperature <37oC or >37oC
Thermoreceptor Skin
Conscious area of brain
Somatic NS
Skeletal muscles
Behavioural response
Response
Changing heat gain or heat loss adjusts body temperature
stimulus
Regulation
Transmission
Response to high core temperature
Effector
Core temperature ˃37 o C Thermoreceptors
Hypothalamus
Surface blood vessels Sweat glands
Vasodilation Sweating
Reduced heat production & increased heat lossreturns core temperatureto normal
Stimulus
ModulatorControl centre
Response
Negative
feedback
Receptor
Response to low core temperature
Effector
Core temperature <37 o C Thermoreceptors
Hypothalamus
Surface blood vessels
Skeletal muscles Vasoconstriction
PiloerectionShivering
Reduced heat loss & Increased heat productionreturns core temperatureto normal
Stimulus
ModulatorControl centre
Response
Negative
feedback
Receptor