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.