Health

• Communicable disease


  A disease that can be passed from one organism (person) to another, i.e. spread among people
• Communicable diseases are also described as infectious diseases
• Causes of most communicable diseases

  • Bacteria
  • Viruses
  • Fungi
• Communicable diseases in Table 13.1


  • HIV (which leads to AIDS)
  • Colds and flu
  • Human papilloma virus (HPV)
  • Salmonella food poisoning
  • Tuberculosis
  • Chlamydia
  • Athlete's foot
  • Potato blight
• Potato blight is a plant disease that affects the potato and similar plants - all the other communicable diseases in Table 13.1 are passed among humans
• Skin


  • Barrier that stops microorganisms entering the body
• Mucous membranes


  • Thin membranes in the nose and respiratory system that trap and expel microorganisms
• Clotting


  • Closes wounds quickly to form a barrier that stops microorganisms gaining entry (also prevents loss of blood)
• Lymphocytes


  White blood cells that produce antibodies when microorganisms enter the blood
• Antigen


  Distinctive marker on a microorganism that leads to the body producing specific antibodies
• Antibody


  Structure produced by lymphocytes that has a complementary shape (and can attach to) antigens on a particular microorganism
• Memory lymphocyte


  Special type of lymphocyte that can remain in the body for many years and produce antibodies quickly when required
• Antibody action


  1. Microorganisms have special 'marker' chemicals on their surface called antigens

  2. These antigens cause the lymphocytes (white blood cells) to produce antibodies

  3. The antibodies are complementary in shape (like a lock and key) to the antigens

  4. The antibodies latch on to the antigens (microorganisms), linking them together

  5. This immobilises (clumps) the microorganisms and they can then be destroyed
• Phagocytosis


  Process where phagocytes (a type of white blood cell) surround and engulf, then digest, microorganisms
• Primary response


  Individuals infected by a disease-causing bacterium or virus are often ill for a few days before the antibody numbers are high enough to provide immunity
• Secondary response


  Once infected, the body is able to produce memory lymphocytes that remain in the body for many years, allowing them to produce antibodies very quickly to stop the individual catching the same disease again
• Active immunity


  The type of immunity produced when the body produces its own antibodies
• Passive immunity


  Immunity produced by injecting antibodies from another source (e.g. pharmaceutical companies)
• Vaccination


  1. Involves the use of dead or modified disease-causing microorganisms (pathogens) that are injected into the body

  2. Antigens on the dead or modified pathogen cause the body to produce antibodies

  3. This raises antibody levels in the blood

  4. If the body becomes infected with the disease-causing microorganism at a later date, memory lymphocytes cause the body to rapidly produce antibodies to prevent disease developing
• Sometimes we need more than one vaccination to make sure that we remain immune for a reasonable period of time. This is known as a follow-up booster
• Antibiotics


  Chemicals produced by fungi that are used against bacterial diseases to kill bacteria or reduce their growth
• Bacteria can evolve (change) so that antibiotics no longer have an effect
• Overuse of antibiotics has been a major factor in the development of bacterial resistance to antibiotics (and the development of 'superbugs')
• MRSA is a type of bacterium that is resistant to most antibiotics - an example of a superbug
• Antibiotic-resistant bacteria have been a particular problem in hospitals
• Antibiotic resistance


  • Bacteria can mutate and change their DNA to develop new properties that make them resistant to antibiotics
  • Antibiotics will not work against these particular bacteria, or cure diseases caused by them
• Superbug


  • MRSA
• Procedures to reduce the incidence of superbugs

  1. Not overusing antibiotics when not needed (e.g. against viral diseases)

  2. Increased hygiene measures in hospitals, e.g. staff and visitors washing hands or using hand gels

  3. Isolating patients infected with MRSA or other 'superbug' infections
• Aseptic techniques


  Procedures used to avoid contamination of cultures and the growth of unwanted, pathogenic microorganisms
• Using aseptic techniques when transferring microorganisms

  1. Pass the metal loop through the flame of the Bunsen burner

  2. Allow the metal loop to cool

  3. Remove the lid of the culture bottle (Tube A) and glide the loop over the surface of the agar (without applying any pressure)

  4. Replace the lid of the culture bottle to prevent contamination

  5. Spread the microbes over the surface of the agar in the Petri dish (B) by gently gliding the metal loop over the nutrient agar surface

  6. Heat the metal loop again to a high temperature to ensure that any microorganisms remaining on the loop are destroyed

  7. Tape the Petri dish and then incubate it in an oven at 25°C

  8. Work close to a Bunsen burner to create an upward current of air that carries microorganisms away from the area

  9. Clean all work surfaces and hands and safely dispose of bacterial cultures
• Instead of using a metal loop, it is possible to use sterile disposable plastic loops that do not require heating
• All the apparatus used, e.g. agar plates, should be sterilised in advance, or disposable sterile plates should be used
• Non-communicable diseases


  Diseases that are not passed from person to person - they are not infectious diseases
• Lifestyle factors


  Factors that can contribute to non-communicable diseases, such as poor diet, lack of exercise, overexposure to UV radiation, alcohol, and tobacco smoke
• Harmful effects of tobacco smoke

  • Tar causes bronchitis, emphysema, and lung cancer
  • Nicotine is addictive and affects the heart rate
  • Carbon monoxide combines with red blood cells to reduce the oxygen-carrying capacity of the blood
• Heart disease


  • Caused by the build-up of cholesterol or fat in the coronary arteries, which narrows them and prevents the heart muscle from receiving enough oxygen and glucose, leading to cell death and inability to contract
• Strokes


  • Caused by blood vessels becoming blocked, resulting in the death of brain cells and reduced brain function
• Lifestyle factors that contribute to cardiovascular diseases


  • Excess dietary fats
  • Smoking
  • Lack of exercise
  • Stress
• Angioplasty


  A medical technique involving the use of balloon-like structures to hold open diseased arteries so that stents (small mesh-like structures) can be inserted into the blood vessels to keep them open
• Statins and aspirin


  Drugs that can help protect against cardiovascular disease - statins help reduce blood cholesterol and aspirin helps 'thin' the blood and makes it less 'sticky'