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.