B2- Keeping healthy


Microorganisms and disease

  • Infectious microorganisms produce toxins that damage cells.
  • To reproduce, bacteria needs a source of nutrients for energy, and a warm, moist condition.
  • Viruses need other cells to reproduce.
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The immune system

  • The role of the immune system is to deal with any infectiou microorganisms that enter the body.
  • Anything that gets into the body is picked up by white blood cells, these can detect things foreign to the body, they then engulf these microbes and digest them.
  • The white blood cells are non-specific and attack anything not meant to be there.
  • A different type of white blood cells attack specific microorganisms. These have specific receptors that recognise antigens, and then produce antibodies, that are specific to the antigens. These antibodies then either; mark the microorganism so that a white blood cells engulfs it, bind to it a neautralise it, or kill them directly. 
  • Some white blood cells stay in the blood after the infection has been fought off. These are memory cells. They can reproduce quickly if the same antigen invades again.
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  • Vaccinations use a safe version of a dangerous microorganism.
  • Immunisation involves injecting a dead or inactive microorganism, which still carry the same antigens, so your body produces the antibodies to attack them.The white blood cells, memory cells remember these antibodies so that when the microorganism invades they can quickly attack.
  • Epidemics can be prevented by vaccinating lots of people, as there is no longer enough people to pass the disease on.
  • Vaccines and drugs have different effects on different people, so they can never be completely safe.
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  • Chemicals that inhibit the growth of microorganisms or kill them.
  • Antibiotics are a type of antimicrobial that can kill bacteria, however they don't kill viruses (flu and colds)
  • However microorganisms can  evolve and become resistant to antimicrobials.
  • The more often antibiotics are used the more microorganisms can resist.
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Drug trials

  • Drugs are tested first in laboratories.
  • They are developed using human cells to see their effect on real human cells.
  • They are then tested on two different species of live mammals (Monkeys and rats)
  • Drugs are then tested on humans in clinical trials. Firstly on healthy volunteers to see if there is any harmful side effects on a healthy body, and then on people actually suffering from the illness.
  • Placebos are 'fake' treatments, which enables you to see the difference between what people think and what the drug actually does.
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The circulatory system

  • The heart and blood vessels supply blood to the body.
  • The right side of the heart pums deoxygenated blood to the lungs to collect oxygen. And the left side pumps oxygenated blood around the body.
  • Blood is supplied to the heart by two coronary arteries, which branch from the base of the aorta.
  • Arteries carry blood away from the heart to the body cells, they have strong and thick walls.
  • Veins carry blood back to the heart, they have thinner walls than arteries and have valves to keep the blood going in the right direction.
  • Capillaries are branches of arteries that are really tiny, they have permeable walls to let substances diffuse in and out. Their walls are only one cell thick.
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Heart rate and blood pressure

  • Your pulse rate can be used to measure your heart rate.
  • Your heart rate is the number of times that your heart beats per minute (BPM)
  • Your pulse rate is the number of times that an artery pulsated in one min.
  • When your heart muscle contracts, blood is forced out pf the heart this increase the pressure of the blood.
  • High blood pressure increases the risk of heart disease.
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Heart disease

  • Lifestyle factors can increase the risk of heart disease.
  • Poor diet; Cholesterol makes up a large part of fatty deposits that form in arteries. High blood cholestrol is linked to eating foods high in saturated fats. A diet high in salt also increase blood pressure and the risk of heart disease.
  • Smoking; Carbon monoxide and nicotine increase the risk of heart disease. Carbon monoxide reduces the amount of oxygen the blood can transport. Nicotine increases heart rate.
  • Stress; This can increase blood pressure and risk of heart disease.
  • Regular moderate exercise reduces the risk of heart disease, because it burns up fat and strenghtens the heart muscle.
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  • Homeostastis- Maintaning a constant internal environment.
  • Conditions inside the body need to be kept steady, even when external environment changes.
  • There is a automatic control system to regulate your internal environment, made up of; Receptors, Processing centres and effectors.
  • Keeps your internal environment stable using a mechanism called negative feedback. When the level of something gets too high or to low your body uses negative feedback to get it back to normal.
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Controlling water content

  • Water levels in cells is very important. Your body needs to maintain the concentration of its cell contents at the correct level for cell activity.
  • Inputs- Water can be gained for drinks, food and respiration.
  • Outputs- Water can be lost through sweating breathing, in faeces and in urine.
  • Kidneys play a vital role in balancing levels of water.
  • They filter small molecules from the blood, and resorb things like all sugar and as much water and salt the body needs. Whatever isn't absorbed forms urine.
  • The concentration of urine depends on theconcentration of the blood plasma.
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  • The concentration of urine is controlled by a hormone called anti-diuretic hormone (ADH). This is released into the bloodstream by the pituitary gland.
  • The brain monitors the water content of the blood and instructs the pituitary gland to release ADH according to how much is needed.
  • It is controlled by negative feedback.
  • The more water your kidneys reabsorb the less water will pass out as urine.
  • ADH production can be affected by drugs.
  • Alcohol supresses the production of ADH so the kidneys absorb less water. Which means more water is passed as urine and the body gets dehyrated.
  • Ectasy increase ADH production, meaning the kidneys reabsorb more water and less water is passed as urine.
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