HOMEOSTASIS

Noadswood Science, 2012

HOMEOSTASIS To know how the body controls internal conditions

Wednesday, April 19, 2023

WASTE 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…

HOMEOSTASIS Homeostasis is the maintenance of a constant internal

environment

There are six different bodily levels which must all be controlled: -

Removal of CO2 (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)

ENZYMES 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

CONTROL How does your body control is temperature?

TEMPERATURE 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…

SWEATING 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

TEMPERATURE 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

TEMPERATURE 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

TEST 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

WATER 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

WATER 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

LEAH BETTS Leah Betts died a few days after her 18th 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

LEAH BETTS