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Introduction to Homeostasis.

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Presentation on theme: "Introduction to Homeostasis."— Presentation transcript:

1 Introduction to Homeostasis

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

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

4 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


6 Organization of a Human
cells  tissues  organs  organ systems


8 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). Monitor Coordinating centre Regulator Normal balance Change in balance

9 Homeostasis Example: household thermostat
Room T at 22 oC T below: thermostat turns on the furnace T above: thermostat turns off the furnace

10 Example: household thermostat
Detects decrease in temperature Monitor- Thermometer Coordinating centre- Thermostat switches on furnace Regulator- Furnace Thermostat detects temperature increases over “normal” Furnace turns off Whole control system is called a negative feedback system

11 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?

12 Negative Feedback Example: Thermoregulation of body
The maintenance of body temperature within a range that enables cells to function efficiently Heat Stress Cold Stress

13 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.

14 Dilation allows for more blood flow to the skin.
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.

15 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

16 Thermoreceptors message the hypothalamus
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. Smooth muscle contract that surrounds the hair follicles in your skin causing the hair to “stand on end” trapping warm air. Skeletal muscle to contract causing shivering and increasing your metabolism to make heat.

17 Cold stress Monitor: Thermoreceptors Coordinating centre: Hypothalamus Regulator: skin blood vessels constrict and skeletal muscles contract Result: body temperature increases and hypothalamus turns off.


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