Homeostasis

Introduction to

A Cooling Glove  The heat extractor increases heat loss and allows the body to perform at a higher level in severe conditions.

Core Temperature

• Humans have a normal temperature of around 36.2 to 37.2 degrees Celsius– Above (hyperthermia): infection– Below (hypothermia): cell death

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http://news.bbc.co.uk/2/shared/spl/hi/health/03/travel_health/diseases/html/sars.stm

What is Homeostasis?

• The body’s attempt to maintain “normal” levels within your body, despite environmental differences

• dynamic equilibrium- a mechanism to ensure that all body systems function within an acceptable range to sustain life

http://balancewines.wordpress.com/2009/12/

Organization of a Human

cells tissues organs organ systems

Homeostatic control systems• 3 components:

– Monitor(receptors)

– Coordinating centre(brain)

– Regulator(muscles, glands etc.)• Monitors send signals to the

coordinating centre that the normal levels have changed (sensory pathway).

• The coordinating centre then messages the regulator which helps restore normal balance (motor pathway).

HomeostasisExample: household thermostat

• Room T at 22 oC – T below: thermostat turns on the

furnace– T above: thermostat turns off the

furnace

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Example: household thermostat

Whole control system is called a negative feedback system

Negative feedback• Process by which a mechanism is activated to restore

conditions to their original state• It ensures that small changes don’t become too large.

– Why is a thermostat a negative feedback system?

Negative FeedbackExample: Thermoregulation of body

• The maintenance of body temperature within a range that enables cells to function efficiently–Heat Stress–Cold Stress

Heat stress• Thermoreceptors (PNS)

detect an increase in body temperature

• Hypothalamus (CNS) signals to the sweat glands to initiate sweating.

• Evaporation of the sweat off the skin causes cooling.

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Heat Stress• The hypothalamus also sends message

to blood vessels in the skin causing them to dilate.

• Dilation allows for more blood flow to the skin.

• Heat from the blood is lost to the skin so blood can return to core of your body & cool the internal organs.http://www.pgbeautygroomingscience.com/functions-

of-the-dermis.html

Heat Stress • Monitor: thermoreceptors

• Coordinating centre: hypothalamus turns on cooling system

• Regulator: skin blood vessels dilate and sweat glands initiate sweating

• Result: body temperature decreases; hypothalamus turns off cooling system

Cold stress• Thermoreceptors message the

hypothalamus

• Hypothalamus sends a message via the nerves:– Arterioles of the skin constrict therefore

limiting blood flow =reduced heat loss from the skin and retains heat in the body.

o Smooth muscle contract that surrounds the hair follicles in your skin causing the hair to “stand on end” trapping warm air.

o Skeletal muscle to contract causing shivering and increasing your metabolism to make heat.

http://www.clarian.org/ADAM/doc/HealthIllustratedEncyclopedia/2/19194.htm

Cold stress

• Monitor: Thermoreceptors• Coordinating centre: Hypothalamus• Regulator: skin blood vessels constrict and

skeletal muscles contract• Result: body temperature increases and

hypothalamus turns off.