The circulatory system.
The heart (a muscular organ) pumps blood around the body.
There are 2 separate circulation systems:
- body → heart (pumps the blood) → lungs (where it picks up O2 and loses CO2)
- lungs → heart (pumps blood) → body
Arteries take blood away from the heart.
Veins take blood to the heart.
Capillaries are tiny blood vessels that are between arteries and veins, they carry the blood through organs and allow the exchange of substances with all living cells in the body.
Transport in the blood.
Red blood cells transport O2.
The red pigment in them is called haemoglobin.
They have no nucleus.
In the lungs haemoglobin combines with O2 to form oxyhaemoglobin.
When cells respire the oxyhaemoglobin breaks back down to release O2 for repspiration.
Blood plasma transports:
- CO2 (to the lungs)
- urea (made by the lungs, excreted by the kidneys)
- the (soluble) products of digestion (to cells)
The effect of exercise on the body.
During exercise muscles need more energy so that they can contract.
More glucose and O2 need to be transported to the muscle cells and CO2 needs to be removed more quickly during exercise.
To do this there are changes in :
- heart rate (increases)
- breathing rate (increases and depth of each breath increases)
- blood supply ( blood vessels dilate)
Also gycogen can be used up (a storage compound of glucose).
Muscles become fatigued due to lots of exercise.
When they cannot get enough O2 they begin to respire anaerobically.
Anaerobic respiration is very inefficient and it produces lactic acid which causes fatigue.
Lactic acid must be completely broken down after exercise by O2 which oxidises lactic acid into CO2 and H2O.
So you need a lot of oxygen to do this, this is called the 'oxygen debt'.
The human kidney.
The body has 2 kidneys.
Chemical reactions in the body produce substances that are toxic.
The kidneys excrete these substances that the body does not want.
Th kidneys first filter substances out of the blood and then reabsorb the substances (like sugar, water and dissolved ions) that the body needs.
Sometimes reabsorption is doen againts the concentration gradient (Active Transport).
Urea is made by the liver from excess amino acid, it is toxic.
Urea is dissolved in urine which is excreted by the kidneys.
The bladder stores urine.
Urethra is the tube that urine passes out of the body.
Dialysis machines do the work of a kidney and keeps the patient alive.
The blood flows through partially permeable membranes.
Dialysis fluid contains the same concentration of useful substances that the patients blood has (glucose and mineral ions).
This means they do not need to be filtered out of the blood so do not need to be reabsorbed.
Urea does get filtered out.
Dialysis restores the concentration of substances in the the blood back to normal but needs to be carried out regularly.
If a successful kidney transplant takes place then the patient will no longer need the dialysis machine.
A diseased kidney can be replaced with a healthy one.
The healthy kidney must be a very good 'tissue match'.
The immune system must be suppressed to stop rejection:
- the patient's bone marrow is treated with radiation to stop white cell production.
- the patient will have to continue to take drugs (immunosuppressant drugs).
- the patient must be kept in sterile condidtions to prevent infection