B4

Homeostasis = maintenance of a constant internal environment.

Can be affectedby exercise, temperature, blood oxygen levels and salt levels.

Artificial Homeostasis = needed when the body's control systems dont work correctly.

Incubators = help premature babies to survive by controlling temperature and oxygen levels.

Artifical and body systems have ....

- receptors

- processing centres

- effectors

Negative Feedback = maintenance of a steady state by reversing the change in conditions.

Antagonistic Effectors = act as opposites to one another.

Hot climates = body temperature too high = sweating

Cold climates = body temperature too low = shivering

Hypothalamus = part of the brain responsible for maintaining homeostasis.

Vasodilation = blood vessels in skin dilate in hot conditions

Vasoconstriction = blood vessels in skin constrict in cold conditions

Heat Stroke = an uncontrolled increase in your body temperature.

Hypothermia = cause when core body temperature falls below 35 degrees celcious

Kidneys = filter your blood to remove urea and to balance levels of water and chemicals

Water level high - kidneys reabsorb less water - large amount of dilute urine

Water level low - kidneys reabsorb more water - small amount of concentrated urine

Amount of water that needs to be reabsorbed into blood plasma depends on ....

- external temperature

- exercise

- fluid intake

- salt intake

Alcohol causes large amount of dilute urine to be produced

Ecstasy causes small amount of concentrated urine to be produced

Anti Diuretic Hormone = controls concentration of urine. Released into your blood via the pituitary gland.

Alcohol - ADH suppressed - more water leaves the body in urine

Ecstasy - too much ADH produced - too much water remains in the blood

Diffusion = movement of substances from high to low concentration

Substances that move in and out of cells by diffusion include....

- oxygen

- carbon dioxide

- dissolved food

Osmosis = movement of water from high to low concentration

Active Transport = movement of substances against a concentrated gradient (requires energy)

Enzymes = protein molecules that speed up the rate of chemical reactions in cells.

Denatured enzyme = structure of the enzyme is permanently destroyed and stops working.

Active Site = place where the molecule fits into the enzyme

The shape of the active site is affected by...

- heat

- pH level