Homeostasis

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

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

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

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

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

Quick Questions Get a pen and paper ready

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

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.

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

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

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

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

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

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

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

Question is do we know how ENERGY is transferred?

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

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

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)

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