Louis Chow

ThermoregulationHOMEOSTASIS

Homeostasis

The ability of the body to maintain a constant internal environment despite fluctuations in both the body’s activities and the external environment

Consists of specific values which are considered as normal

What is it?

Significance? Enables organisms to explore inhospitable

environments

Negative Feedback Mechanism...

Negative feedback mechanism1. Receptors detects a stimulus (external or internal change).

2. Communication between the receptor and the effector(through a control centre).

3. Effector brings about the response to restore balance.

4. When the response is enough to return the body back to its normal state, the receptor is turned off.

Why control body temperature?

Independence from changing environments Affects the rate of metabolic reactions Sensitivity of enzymes

Ectotherms Ectotherms: Fish, amphibians, reptiles etc. Body temperature is greatly dependent on the

external temperature Variable metabolic rate Activity levels determined by external

environment

Behavioral responses

Voluntary responses Temperature too cold: cuddling, put on more

clothes, eating, more muscular activities, move closer to heat sources, e.g the Sun

Temperature too hot: Less clothing, cool drinks, find shades, body orientation

EndothermsEndotherms:

• Mammals and birds

• Body temperature is less dependent on the external temperature

• High metabolic rate

• Possess thermoregulating mechanisms

Physiological adaptions

controlled by the thermoregulatory centre in the hypothalamus.

Receptors in the hypothalamus itself(blood temperature, the core temperature)

Skin receptors (the external temperature) Also controlled by the cerebral cortex -- Voluntary

actions

Heat gain vs heat loss

Heat Exchange between organisms and their surroundings:

Core temperature and skin temperature

• http://www.youtube.com/watch?v=Vlp_NHuC0rw

Thermoregulation

Hot: decrease heat gain

Increase heat loss

Cold: Increase heat gain

decrease heat loss

Pilorelaxation and Piloerection

Relaxation of erector muscle Contraction of erector muscle

Vasodilation and Vasoconstriction

Hot: Skin arterioles dilate

Sphincter muscles relax

Shunt vessels constrict

Blood flow to skin capillaries increased

Cold: Skin arterioles constrict

Sphincter muscles contract

Shunt vessels dilate

Blood flow to skin capillaries decreased

Sweat productionHot: Activation of sweat glands

Increased sweat production

Cold: Inhibition of sweat glands

Decreased sweat production

Extreme temperatures

Hypothermia Core temperature falls

below 35 degrees Celsius

Enhanced by alcoholic effects

Amnesia, death

Hyperthermia Core temperature higher

than 38.5 degrees Celsius

Adverse effects by drugs

Heat stroke

Dizziness, confusion

Preventing hypothermia

Wear more clothes!! Avoid diving in cold water Go closer to heat sources

Preventing hyperthermia

Find shades Avoid excess exercise

What might come in the exam..

Where is the best place to take a temperature of a person?

Define evaporative heat loss. Describe and explain a way of losing heat.

THE ENDThank you!