H OMEOSTASIS Noadswood Science, 2012

H OMEOSTASIS To know how the body controls internal conditions Sunday, August 30, 2015

W ASTE What waste products does the human body produce? Faeces Urea Carbon dioxide It is vital that all of these materials are removed from the body to maintain its healthy functioning…

H OMEOSTASIS Homeostasis is the maintenance of a constant internal environment There are six different bodily levels which must all be controlled: - Removal of CO 2 (waste product) Removal of urea (waste product) Ion content (must remain at correct level) Water content (must remain at correct level) Sugar content (must remain at correct level) Temperature (must remain at correct level)

E NZYMES Enzymes work best at 37°C, so the body’s temperature needs to be controlled The thermoregulatory centre within the brain monitors and controls body temperature, gathering information as nerve impulses from temperature receptors in both the brain and the skin The brain - sensitive to the temperature of the blood flowing there The skin - sensitive to skin temperature

C ONTROL How does your body control is temperature?

T EMPERATURE If you become too hot or too cold, there are several ways in which your temperature can be controlled They involve sweating, shivering, skin capillaries and hairs…

S WEATING Sweating is one way to help cool the body – we sweat more in hot conditions, so more water is lost from the body Water must be replaced through food or drink to maintain the balance of water in the body Ions such as sodium and chloride ions are also lost when we sweat which must be replaced through food and drink If the body’s ion content is wrong, cells can be damaged

T EMPERATURE Too hot: - Sweat glands in the skin release more sweat which evaporates, removing heat energy from the skin Blood vessels leading to the skin capillaries dilate and become wider allowing more blood to flow through the skin, and more heat to be lost Too cold: - Muscles contract rapidly (shiver), which require energy (from respiration) with some of this energy released as heat Blood vessels leading to the skin capillaries constrict and become narrower letting less blood flow through the skin and conserving heat in the body

T EMPERATURE Skin capillaries and hairs help regulate temperature… The hairs on the skin also help to control body temperature – they lie flat when we are warm, and rise when we are cold The hairs trap a layer of air above the skin, which helps to insulate the skin against heat loss

T EST Place your hands in cold water and then in warm water – notice what happens to your blood vessels: - In warm water they dilate and become wider In cold water they constrict and become narrower

W ATER Water enters the body through food and drink as well as being a product of aerobic respiration in cells If the amount of water in the body is wrong, cells can be damaged because too much water enters or leaves them

W ATER Water and ions enter the body when you eat / drink The water and ion content of the body must be carefully controlled to prevent damage to the cells Water is lost through breathing, sweating and in the urine Ions are lost through sweating and urine If the water or ion content of the body is wrong too much water may move in / out of the cells, as well as the importance of water to help control core temperature and the sugar levels within the blood

L EAH B ETTS Leah Betts died a few days after her 18 th birthday after taking an ecstasy tablet – 4 hours after taking it she collapsed into a coma from which she did not recover Her death was caused by water intoxication - a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside of safe limits by over-consumption of water

L EAH B ETTS