Post on 23-Feb-2016
description
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!