1. Homeostasis

2. Syllabus Point - 16
Discuss the concept of homeostasis and its importance in maintaining the body n a state of dynamic equilibrium during exercise, including the role of the hypothalamus and the mechanisms of thermoregulation

3. What is Homeostasis?
The maintenance of a stable internal environment in order for cells to function properly

4. What stable conditions are achieved within the blood?
Concentrations of glucose
Ions
Carbon dioxide
Water potential pH
Temperature

5. Syllabus Point - 15
Explain the principle of negative feedback in maintaining systems within narrow limits

6. All About Negative Feedback
Receptors used to detect deviations from the norm
Control Mechanism
Negative Feedback
Condition is brought back to norm
Effectors are turned on/off

7. Quick Questions
Get a pen and paper ready

8. What is thermoregulation?
What is our core body temperature?
Why is our body temperature so important?

9. Thermoregulation
What is thermoregulation? The control of body temperature What is our core body temperature? 37.5°C Why is our body temperature so important? 37.5°C allows all enzyme-controlled reactions to happen at a reasonable rate for the body to remain active. Lower temperatures decrease the reaction time and higher temperatures denature enzymes.

10. Temperature and Negative Feedback
Maintains
Temperature
through the changes in blood temperature

11. Nerves from hypothalamus stimulate sweat glands
HEAT
Nerves from hypothalamus stimulate sweat glands
Sweat duct evaporates releasing sweat taking heat energy from skin

12. Hairs COLD Contractions of erector muscles causes hairs to rise
Air is trapped – insulating the body
Trapped Air

13. Vasoconstriction Arterioles constrict Arteriole walls contract COLD
Blood supply is reduced
Not so cold???
Diversion causes shunt vessel to dilate as blood flows through it
Less energy is lost
Blood now flows further away from the skin surface

14. Test Yourself… Vasodilatation is the opposite to Vasoconstriction.
Vasodilatation occurs when the conditions are warmer.
Can you explain what would happen to the:
Shunt vessel
Muscles in the walls of arterioles
The blood flow
Energy

15. Now check your version with the one given on the next slide

16. Vasodilatation WARM Arteriole walls contract Shunt vessel constricts
Feeling cool?
Blood flows through the arterioles causing them to dilate
Less energy lost
Blood flows closer to the skin surface

17. Question is do we know how ENERGY is transferred?

18. In which ways do you think that ENERGY is transferred?
Quick Question
In which ways do you think that ENERGY is transferred?

19. Four Ways of Energy Transfer:
Conduction
Convection
Evaporation
Radiation
Involves direct contact form one object to the other where energy is lost from one another
Energy loss by bulk movement of air
Air next to the skin will be warmed by the body
As air expands it rises being replaces by cooler air which is then armed by the body
Thermal insulation via clothing or trapping of is reduces convection
Sweat evaporation increases energy loss
Evaporation of moist surfaces of lungs increases energy loss
When air is saturated with water vapour energy loss by evaporation becomes difficult
Our bodies are usually warmer than our surroundings so we radiate energy
However, we are also warmed by the energy radiated from the Sun

20. Questions Suggest how reduction of blood flow may occur? (1 Mark)
Suggest the effect of reduced blood flow through the skin on the body temperature? (1 Mark)
During exercise how does the body control its temperature? (3 Marks)

21. Answers Vasoconstriction Less heat is lost by convection and radiation
Hypothalamus detect changes in temperature which causes:
Sweating and evaporation
hair erector muscles to relax
Which allows more heat to be lost