December 13, 2010 BellRinger
Read essay “behavior of homeostasis” pg. 239-241 What is the difference between an ectotherm and an
endotherm?
Objectives Differentiate between endotherm and ectotherm Describe the components of a feedback system
Homework: Study for exam (Wed)
How Do They Stay so Cool? Read intro p. 188-189 Watch DVD “Temperature regulation in
animals” Record notes in journal (use chart on p. 189)
How do different organisms maintain temperature balance? Warm-blooded
(endotherms) Cold-blooded
(ectotherms)
ThermoregulationThermoregulation(Regulation of Body (Regulation of Body Temperature)Temperature) poikilotherms (cold-blooded animals)
body temperatures vary with that of the environment
e.g. reptiles, fish, amphibians
Homoiotherms (warm-blooded animals) keep body temperature constant even
in winter by increasing metabolic rate e.g. birds, mammals
ThermoregulationThermoregulation(Regulation of Body (Regulation of Body Temperature)Temperature)
Temp Regulation - Temp Regulation - HomeostasisHomeostasis Why must organisms maintain internal temp
balance? Enzymes!!
Enzymes speed up chemical rxns in your body Enzymes only work under certain conditions
Body TemperatureBody Temperature Normal internal body T is 370C T above this:
denature enzymes, block metabolic pathways
(denature = unravel) T below this:
slow metabolism and affect brain
METABOLISM: chemical changes that occur in a cell or an organism that produce energy
You will learn more about this after break!
Thermostat
Temperature set on thermostatToo cool? Heater kicks on and temperature goes up
Too warm? Stays off until house cools downConstant checking and turning on and off
Control of homeostasis Control of homeostasis through feedbackthrough feedback
Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re-monitored, re-evaluated, etc.
1) receptor sensor that responds to changes (stimuli)
2) control center sets range of values, evaluates input and
sends output 3) effector
receives output from control center and produces a response
3 basic components of a feedback system
Body Temperature Control The hypothalamus
acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin.
There are also receptors in the hypothalamus- called central thermoreceptors. These detect changes in
blood temperature.
Summary What is the difference between an ectotherm
and an endotherm? What are the components of a feedback
system?
Homework: Study for exam
Maintenance of Body Maintenance of Body TemperatureTemperature
Epidermis
Dermis
Outermost layerMiddle layerInnermost layer
Sweat gland
Blood capillaries
Subcutaneous fat
Receptors
Erector muscle
Nerve fibres
Sebaceous gland
Hair follicle
Structure of Mammalian Structure of Mammalian SkinSkin
Vasoconstriction and VasodilatationVasoconstriction and Vasodilatation
Correction of Correction of overheatingoverheating1. Detected by thermoreceptors in
the hypothalamus.2. Causes vasodilation.3. Sweating
SweatingSweating
How does it work?
Heat energy in the body is used to convert the water in sweat to vapour cooling down the body.
Heat Loss Radiation: Transfer of
heat via infrared rays 60% heat loss at rest
Conduction: Heat loss due to contact with another surface
Convection: Form of conductive heat loss
Heat Loss Evaporation
Heat transferred via water (sweat) on skin surface
Evaporation rate depends on Temperature and relative humidity Amount of skin surface exposed
25% heat loss at rest
Most important means of cooling off during exercise
DehydrationJOSH!
1% = rapid ↑ in temp (heat stroke) 2% = ↓ performance 3% = ↓ coordination 4% = headache/nausea 5% = failure of thermoregulation 6% = serious risk for collapse, permanent
injury, & organ failure
Correction of overcooling1. Detected by thermoreceptors in the hypothalamus.
2. Causes vasoconstriction.3. Decreased sweating4. Shivering
Keeping warmKeeping warm
When it's cold, the muscle contracts pulls the hair up.
A layer of warm air accumulates around the hair and insulates the organism.
Heat retained
Shivering
How does it work?
Voluntary responsesVoluntary responses
In humans the cerebrum “makes” people feel cold or hot.
They can then e.g. put on more clothes, eat a hot meal, exercise etc as appropriate.
Hypothermia
Summary Describe the specific pathway that is used to
keep us warm. Start with the temperature receptors in the skin.
Describe the specific pathway that is used to cool us off. Start with the temperature receptors in the skin.