HOMEOSTASIS Thermoregulation Louis Chow
What is it? Significance? Enables organisms to explore inhospitable environments 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
Negative feedback mechanism • Receptors detects a stimulus (external or internal change). • Communication between the receptor and the effector(through a control centre). • Effector brings about the response to restore balance. • 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
Endotherms Endotherms: • 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
Core temperature and skin temperature • http://www.youtube.com/watch?v=Vlp_NHuC0rw
Thermoregulation Hot: Cold: Increase heat gain decrease heat loss • decrease heat gain • Increase heat loss
Pilorelaxation and Piloerection Relaxation of erector muscle Contraction of erector muscle
Vasodilation and Vasoconstriction Hot: Cold: Skin arterioles constrict Sphincter muscles contract Shunt vessels dilate Blood flow to skin capillaries decreased • Skin arterioles dilate • Sphincter muscles relax • Shunt vessels constrict • Blood flow to skin capillaries increased
Sweat production Hot: Cold: Inhibition of sweat glands Decreased sweat production • Activation of sweat glands • Increased sweat production
Extreme temperatures Hypothermia Hyperthermia Core temperature higher than 38.5 degrees Celsius Adverse effects by drugs Heat stroke Dizziness, confusion • Core temperature falls below 35 degrees Celsius • Enhanced by alcoholic effects • Amnesia, death
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 END Thank you!