Lecture Nine

Controlling ions, temperature and blood sugar

Your body needs some things to be constant• To keep your cells working proeperly, certain things must be kept at

the right level.• Bodily levels that need to be controlled include; ion content,

temperature, sugar content and water content.

Ion content

• Ions are taken into the body in food, then absorbed into the blood.• If the food contains too much kind of ion then the excess ions can be

removed.• Some ions are lost in sweat, that’s why dogs like your skins because

sweat is salty.• The kidneys will remove the excess from the blood, and dipsosed of

via urine.

Body temperature

• Body temperature is controlled by the brain.• All enzymes have an optimum temperature they work best at. This is

37 degrees for the human body.• There is a thermoregulatory centre in the brain that acts as a

thermostat.• It contains receptors that are sensitive to the blood temperature in

the brain. It also receives impulses from the skin that provide information about skin temperature. The brain will then respond to this information and bring changes in the body`s temperature.

When your too hot..

• Hairs lie flat• Lots of sweat is produced. When sweat evaporates it uses heat from

the skin. This transfers heat from your skin to the environment which cools you down.• Blood vessels close to the surface of the skin widen. This allows more

blood to flow to the surface so it can radiate more heat into the surroundings. This is called “vasodilation”.

If your exposed to high temperatures you could get dehydrates and could get heat stroke which can kill you.

When your too cold..

• Hairs stand on end to trap an insulating layer of air which keeps you warm.• Very little sweat is produced.• Blood vessels near the surface constrict so that less heat can be

transferred from the blood to the surroundings. This is called “vasoconstriction”.• You shiver and the movement generates heat in the muscles.

If your exposed to very low temperatures for a long time, you can get hypothermia which can kill you.

Blood sugar levels

• Eating foods containing carbohydrate puts glucose into the blood from the gut.• The normal metabolism of cells removes glucose from the blood.

Vigorous exercise can remove much more glucose.• A hormone called insulin helps to maintain the right level of glucose in

your blood so your cells get a constant supply of energy.

Quiz Time !!

Name four levels that the body keeps constant by homeostasis.How do ions enter the body and how are they removed?What temperature do enzymes work best at in the human body?What is the “thermoregulatory centre” and where is it located?How does the body respond when you are too hot?How does the body respond when you are too cold?Which foods put glucose into the blood from the gut?What is the name of the hormone which maintains the right level of glucose in the blood?