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  • Created by: LivviR123
  • Created on: 11-05-16 19:32

Microorganisms and disease


Different M.O = different symptoms- damage is done to body's cells.

  • Can damage cells directly and can produce toxins that damage cells either by producing proteins that damage the material holding cells together or producing toxins that poison cells.

M.O REPRODUCE BY MAKING COPIES OF THEMSELVES. They need a source of nutrients for energy, warm and mosit conditions (so chemical reactions can take place inside them) 

  • lots of places inside the human body where those conditons will be found- e.g intenstines
  • Virsuses need other cells to reproduce, they use parts of other cells
  • certain viruses can easily reproduce inside the body as there are the right kinds of cells for them to use.


  • number of M.O before reproduction
  • how long it takes for one M.O to reproduce
  • how long M.O are left to reproduce for.
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The Immune System


  • Immune response always involves WBCs- there are several different types w. different jobs to do. Anything that gets into body should be picked up immediantly by a certai type of WBC. These WBCs detect anything foreign to the body, they engulf the microbes and digest them, these WBCs are non-specific- attack anything that's not meant to be there.

ANTIBODIES ARE PROTEINS SPECIFIC TO A PARTICULAR ANTIGEN- Some WBCs have receptors that recognise particular antigens -ANTIGENS: SUBSTANCES THAT TRIGGER IMMUNE RESPONSES (usually protein molecules on the surface of a microorganism) 

Certain types of WBCs produce antibodies, which latch onto invading microorganisms and either mark the microorganism so other WBCs can engulf and digest it, bind to and neutralise viruses/toxins or attach to bacteria and kill directly. Once the right WBC recognises the antigens on a microorganism, it divides to make more identical cells, which make lots of the right antibody to fight the infection. Memory cells reproduce v quickly if same antigen enters again. Memory cells then produce loads of antibodies and kill of miroorgaisms before peron becomes ill- immunity.

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Vaccinations use a safe version of a dangerous microorganism

  • immunisation involves injecting dead/ inactive microorganisms, these carry the same antigens so body produces antibodies to attack them
  • body also produces memory cells that stay in blood
  • if body is infected, memory cells can quickly kill them off before person suffers with illness.


  • large percentages of population need to be vaccinated
  • people vaccinated < people not vaccinated = higher risk of epidemic
  • less people vaccinated also means the quicker it spreads and harder it is to control.

Side Effects- different effects on different people, never completely safe, genetic differences can cause different reactions.

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  • useul for clearing up infections, antibiotics are a type of A.M that can kill bacteria, but not viruses 


  • random mutation= change in their DNA, can lead to change in characteristic which could mean it is less affected by a A.M. Big advantage for M.O bc it's easier to survive in a host, allows more reproduction. Leads to gene resistance being passed on to offspring- just natural selection- this is how it spreads

ANTI-BIOTIC RESISTANCE -more often A.Bs used = bigger the problem of resistance comes. Important only used when needed: creates a situation where naturally resistant bacteria have an advantage and increase. Important to take all the A.Bs a doctor prescribes you: not finishing + increase risk of antibiotic resistance emerging 

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Drug Trials

1st= tested in a laboratory 

  • new drugs developed a lot, oftenusing human cells that are griwn in the lab, which allows measurement on effectiveness of the drug on human cells, but it can't recreate conditions of a whole system
  • drugs must be tested on 2+ different species of live mammal before given to humans
  • mammals often have similar systems to humans, so indications can be made on the effect

Then on humans in clincal trials 

  • first= healthy bolunteeers, to make sure it doesn't have any harmful side effects when body is working normally
  • second= sufferers of the illness- for safety and effectiveness

PLACEBOS: fake treatments that don't invollve giving the drug to patient


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The Circulatory System

HEART AND BLOOD VESSLES SUPPLY BLOOD TO THE BODY- Oxygen and nutrients are carried in the blood to the body cells and waste substances are carried away from the cells.

HEART: PUMPING OXYGEN- KEEPS BLOOD FLOWING THROUGH VESSELS- a double pump made up of muscle cells. 

Right side: deoxygenated blood to lungs / Left Side: pumps oxygenated blood around body

Three main types of blood vessel:

ARTERIEScarry blood away from heart to body cells, comes out at high pressure so walls are strong and elastic, thicker than the walls of veins

VEINScarry blood back to the heart, blood is at a lower pressure in the veins, bigger luma than arteries to help blood flow more easily, valves keep it flowing in one direction

CAPILLARIES- branches of arteries are v small, carry blood v. close to every cell in the body to exchange substances with- permeable walls, supply nutrients and oxygen, takes away waste, walls are only one cell thick, increases rate of diffusion by decreasing distance over it travels. 

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Heart Rate and Blood Pressure

PULSE RATE: no. of times an artery pulsates per min. 

HEART RATE: no. beats per minute - pulsation of an artery is caused by blood being pumped through it by a heart beat, so iyou can measure your pulse rate to work out heart rate. 

Heart muscle contracts= blood forced out of heart = increases blood pressure, heart msucle relaxes, heart fills with blood and pressure decreases. BP is measured by taking a reading of pressure of blood against walls of an artery, 2 values= Blood when heart contracts over blood when hear relaxes- used to check health, compared to the "norm" For adult, norm=60-100 per min. 

High BP increases risk of heart disease- inner lineling of an artery is smooth and unbroken, HBP dangers it, fatty deposits build up in damaged areas of arteries- deposits restrict blood flow and cause blood pressure in arteries to increase. If a fatty deposit breaks through lining on an artery, a blood clot may form around it, this could block an artery completely, it could also break away and block another. If a coronary artery becomes completely blocked a heart attack will occur as part of the area will recieve no oxygen. Heart attack can cause serious damage to heart/ cause death of the heart- can be fatal. 

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Heart Disease

Lifestyle factors can increase risk of heart disease. 

  • Poor diet- cholestorol makes up a large part of fatty deposits, can form in damaged arteries. Blood cholestorol high = increased risk. HBC level linked to eating foods high in saturates fat. High salt increases risk of HD bc it increases B.P.
  • Stress= long period of time increases B.P, increases risk of heart attack
  • Excessive alcohol drinking= increases risk because it increases B.P
  • Missuse of illegal drugs= drugs like ecstacy and cannabis increase risk bc they increase heart rate which increases B.P
  • Smoking= Carbon monoxide and nicotine in cigarette smoke increases risk of H.D. bc CO decreases amount of oxygen blood can transport. Heart muscle doesn't recieve enough oxygen, can lead to a heart attack. Nicotine increases heart rate, heart contracts more= increase in blood pressure and increases risk of H.D

Regular, moderate exercise reduces risk of H.D- burns fat, preventing build up in arteries- exercise also strengthens heart. Heart disease more common in MEDCs where high fat foods are affordable. Epidemiological tudies cam identify possible risk factors. 

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Homeostasis- balancing inputs and outputs to maintain a constant internal enivronment

  • conditions need to be kepy steady bc cells need the right conditions to function properly.
  • loads of automatic control systems that regulate internal environment- both nervous and hormonal
  • three main components= receptors, processing centres, effectors. 

Negative feedback-a mechanism used  to control internal environment- level of something too high or low, negative feedback brings it back to normal. 

1) Receptor detects a change in environment, level is too high/low

2) Processing centre recieves info. and coordinates a response

3) Effector produces a response which counteracts the change- level decreases/ increases. 

Effectors carry on until notifed to stop by the processing centre. 

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Controlling Water Content Part 1

Balanced water level is v. important because your body needs to maintain the conc. of its cell contents at the correct level for cell activity- inputs= water gained from food, drink and respiration, outputs= sweating, breathing, faeces and urine

Kidneys help balance substances in the body (water, waste and other chemicals)

  • filter small molecules from blood. Reabsorb various things- all sugar, as much salt and water as body requires. Water absorbtion is controlled by the level if the hormone ADH. Anything that isn't reabsorbed forms urine, which is excreted by the kidneys and stored in the bladder

Conc. of urine depends on conc. of the blood plasma, which varies with..

  • external temp-sweat contains water loss, when hot kidneys reabsorb more water into blood, leaves only a small amount of water, quite concentrated urine produced- small amount
  • Exercise- hotter so sweat to cool down, same effect as heat= more conc and small volume
  • Intake of fluids and salts- more salt+nore conc urine, drinking lots= dilute, high volume urine. 
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Controlling Water Content Part Two

ADH- ANTI-DIURETIC HORMONE- controls conc. of urine, releases into bloodstream by the pituitary gland. Brain montiors water content of blood and instructs pituitary gland to releaase ADH into blood. Whole process controlled by negative feedback. 

Receptor detects, processing centre coordinates a response, pituitary gland releases less ADH (if water content is too high) or more ADH (if water content is too low) so kidneys reabsorb less/more water. 

ADH production is affected by drugs- interfere with natural state of affairs.

Alcohol suppresses ADH production so kidneys will reabsorb less water, more water passed out the body as urine, can lead to dehydration. 

Ecstasy increases ADH production, kidneys reabsorb more water, less water can pass out the body as urine. 

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