Understanding the Human Heart and Immune System

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The heart: double circulatory system

Vena cava - body to the heart (DO), pulmonary artery heart to lungs (DO), pulmonary vein - lungs to heart (O), aorta - heart to body (O). Arteries take blood away from the heart, veins take it towards the heart, Pulmonary means lungs. Valves make sure blood flows in a one way direction. Blood goes from heart to lungs to be oxygenated via the pulmonary artery. The now oxygenated blood goes back to the heart via the pulmonary vein to be pumped around the body via the aorta. Once the blood has been round the body, it is pumped to the heart via the vena cava to be sent to the lungs again for oxygenation then the cycle repeats.

Coronary heart disease

The coronary artery supplies blood to the heart (the heart is a muscle), when it gets blocked (with fat) it can lead to CHD and cardiac arrest.


  • Stents - wire mesh cage that is inserted into the artery that expands and pushes the fat to clear a path for blood to flow.
  • Statins - drug which lowers the amount of cholesterol in the blood.
  • Lifestyle change - working out more, eating less fatty foods etc.
  • Bypass surgery - putting an artery around the blocked one, providing an alternate path for the blood to flow.

Risk factors

High cholesterol diet/lack of exercise can lead to CHD. Obesity can lead to T2 diabetes, cancer of the bowel, liver and kidneys. Drinking too much alcohol can lead to liver disease and affect brain function. Smoking can lead to cardiovascular disease, lung disease, CHD and lung, bowel, stomach, mouth and cervical cancer. Some people's genetics can mean they have a higher risk of getting certain diseases.

Making a medicine

  1. Test on cells - is it toxic?
  2. Test on animals - is it toxic? side effects?
  3. Test on healthy volunteers - is it safe? toxic? side effects?
  4. Test on small number of patients - does it work? safe?
  5. Test on more patients - are results reproducible?
  6. Peer review - other scientists test it
  7. Licensed

Antibiotic resistance and immunity

Antibiotics only work for bacteria. Resistance is not the same as immunity. Resistance is when the bacteria survives the antibiotic, due to the development of a genetic mutation that allows it to not be affected by the antibiotic. First antibiotic was discovered by Alexander Fleming (penicillin). Immunity - humans become immune to a disease. This happens when they are exposed to a pathogen, they get ill from the pathogen and then after a while, the WBC manage to kill it off. After it has been killed off, memory cells will be produced and stored in case the pathogen returns. When the person is infected the second time, the memory cells quickly act and kill off the pathogen so quickly, that no symptoms are displayed.


Vaccines work by injecting a dead/weakened virus into the body and allowing the body to fight it off and make memory cells of it, so when the person becomes infected with the virus, the body can very quickly fight off the virus before any symptoms are displayed (the person becomes immune). Vaccines only work for viruses. The vaccine can cause symptoms as even though it is weakened, it may still be able to do some harm.

Bacteria vs viruses

Bacteria reproduce rapidly, can be every 20 minutes. However viruses invade a 'host cell', and reproduce within that. They cannot reproduce outside of a living cell. Bacteria are also a lot larger than viruses. Bacteria are alive, while viruses are 'dead'. Antibiotics are used to kill bacteria, whereas vaccines are used to kill off viruses.

Human defence mechanisms

  • Ear wax - not ideal environment for bacteria to grow in.
  • Tears - have enzymes that digest pathogens.
  • Cilia - in wind pipe to expel mucus.
  • Skin acts as a physical barrier.
  • Stomach acids - too acidic for most pathogens to survive.
  • Scabs - to fix the physical barrier.


  1. Pathogen enters human body
  2. Pathogen makes person ill, they begin to show symptoms while the lymphocytes are trying to make the correctly shaped antibodies to fit to the pathogen's antigen
  3. Correct antibody shape is made by the lymphocyte for the pathogen
  4. The phagocyte then engulfs the pathogen and breaks it down
  5. Person now feels better

Specific communicable diseases

  • Malaria (protist) - from mosquitoes. Symptoms include fever, headache, sweats, chills, vomiting and diarrhea. Treatments/preventions include nets, drugs and mosquito spray.
  • Rose black spot (fungi, plants only) - symptoms include black spots on the leaves. Treatments include fungicide and removing the infected plant.
  • Measles (virus) - symptoms include cough, runny nose, watery eyes and a fever. Preventions - vaccine.
  • Tobacco mosaic virus (TMV, virus, plants only) - symptoms include yellow mosaic patterns on leaves that prevent photosynthesis. Treatment - cutting off infected leaves.
  • HIV/AIDS (sexually transmitted, virus) - symptoms include presence/absence of HIV antibodies, fever, thrush and fatigue. Treatments - drugs.
  • Gonorrhea (sexually transmitted, bacteria) - symptoms are green/yellow abnormal discharge. Treatments - drugs and antibiotics.
  • Salmonella (from raw meat, bacteria) - symptoms are nausea, fever, abdominal pain. Treatments - antibiotics.

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