The maintenance of a constant internal environment

Learning ObjectivesHow you keep conditions inside your body

constant

How cells get rid of waste products

How the body monitors its temperature

How blood sugar level is controlled

The main things that need to be controlled areBody temperatureWater contentSalt contentBlood sugar contentUreaCarbon dioxide

Cooling the Body DownToo hot- enzymes denature, can’t catalyse

cell reactionsCore temperature too high – skin capillaries

dilate More blood flows through skin - flush- lose

heat -radiationToo low- blood capillaries to skin constrict,

reduce blood flow to skin

BODY TEMPERATUREEnzymes in the human body work best at

about 37 C

The brain has a thermoregulator control centre to maintain this

It controls nerve receptors sensitive to blood temperature in the brain

It also receives information from the skin temperature receptors

WATER CONTENTKidneys control amount of water retained in

the body

Act as Filters to keep a balance of a) water, b) urea, c) ions in the blood

SALT CONTENTIons e.g., of sodium are taken into the blood

after digestion of food

This may cause the salt content of the blood to be too high, drawing water into the cells by osmosis

Excess ions are removed from the blood by the kidneys to maintain a correct body water balance

SweatRate goes up if too hotSweat mainly water, salt As water evaporates, it cools the skinHeat is lost from the body in sweatIn humid conditions, sweat does not evaporate very

easily

BLOOD SUGAR

Eating foods containing carbohydrate means the carbohydrates are digested into sugars which are absorbed into the blood

Levels of blood glucose must be controlled

Insulin is the hormone which controls the level of sugar in your blood.

Regulation of blood GlucoseThe pancreas detects sugar levels

If they are too high the cells in the pancreas secrete insulin

Insulin causes liver and muscles to take up glucose to form glycogen this is the form the energy is stored

Insulin causes the blood glucose levels fall

Pancreas and Insulin

DiabetesA person who has this does not produce

enough of the hormone insulinSo their blood sugar levels can rise to a

fatally high levelThis can cause come and death

Treatment of DiabetesCareful attention to diet

Injecting insulin into the body

Frederick Banting and Charles Best

Experiments carried out by Frederick Banting and Charles BestThese were the first scientists to isolate

insulin

They removed a pancreas from a dog and took an extract from it

They injected this extract into diabetic dogs and observed the effects on blood sugar levels

They found that it caused the dogs blood sugar levels to drop dramatically

What was in this dogs pancreas?The chemical was isolated and it was

INSULIN

Today genetically modified bacteria are used to manufacture human insulin

Check your KnowledgeWhich organ detects blood sugar levels?What hormone does it secrete?What does this hormone convert blood sugar

toWhy is this such an important hormone? Where does this conversion of blood sugar to

glycogen take place?

UREA

Surplus amino acids from digestion are converted to fats and carbohydrates in the liver

The Liver produces the waste product – urea which travels in the blood to the kidneys.

The kidneys filter it out of the blood. It becomes concentrated, to be excreted as urine

CARBON DIOXIDECarbon dioxide is a waste product of

respiration

This is breathed out from the lungs, some dissolved in water vapour.