Health

• Health

  A state of complete physical, mental and social wellbeing
• Types of disease


  • Communicable
  • Non-communicable
• Pathogen

  An organism that causes an infectious disease
• Types of pathogens


  • Bacteria
  • Viruses
  • Fungi
  • Protists
• Bacteria


  • Much smaller than human cells
  • May release toxins that make us feel ill
  • Some types invade and destroy body cells
• Viruses


  • Much smaller than bacteria
  • Take over a body cell's DNA, causing the cell to make toxins or causing damage when new viruses are released from cells
• Fungi


  • Eukaryotic organisms
• How malaria spreads


  1. Infected mosquito bites human and injects protist

  2. Mosquito becomes infected when it takes a blood meal

  3. Mosquito bites second person and spreads malaria
• How HIV spreads


  1. HIV enters blood and reproduces inside white blood cells, causing destruction

  2. Eventually so many white blood cells are destroyed that the immune system cannot work properly, leading to AIDS
• How Ebola spreads


  1. Ebola virus infects humans from other infected people, infected animals or objects that have been in contact with the virus

  2. Virus infects liver cells, cells from the lining of blood vessels, and white blood cells

  3. Virus multiplies inside these cells and destroys them, causing symptoms
• Ways to reduce or prevent spread of pathogens


  • Boil water to kill bacteria
  • Wash hands thoroughly
  • Ventilate buildings adequately
  • Diagnose and treat infected people promptly
  • Isolate infected people
  • Prevent mosquito vectors
  • Cook food thoroughly
  • Wear protective clothing when working with infected people or bodies
• All pregnant women in the UK are screened for HIV infection
• Advantages of screening pregnant women for HIV

  • Allows doctors to give treatment to stop infection getting worse and to try to stop HIV spreading to the baby
  • Gives an estimate of how many people have HIV, which can help target awareness programmes
• Chlamydia


  A sexually transmitted bacterial infection
• How Chlamydia spreads


  1. Can be spread by contact with sexual fluid from an infected partner

  2. Infected mother can pass Chlamydia to baby during birth
• How HIV spreads


  Common methods are unprotected sex with infected partner, sharing needles with infected person, transmission from infected mother to foetus, infection from blood products
• Ways to reduce or prevent spread of STIs

  • Use condoms during sex
  • Screen people, including pregnant women
  • Screen blood transfusions
  • Supply sterile needles to intravenous drug users
  • Treat infected people with antibiotics
• About 3000 15-year-olds are diagnosed with Chlamydia every year
• Better health education in schools


  Could reduce rate of Chlamydia infection in 15-year-olds
• Physical barriers


  Defences that make it hard for pathogens to enter the body
• Chemical defences


  Chemicals produced to kill pathogens or make them inactive
• Physical barriers

  • Unbroken skin
  • Sticky mucus in breathing passages and lungs
  • Cilia that move mucus and trapped pathogens out of lungs
• Chemical defences


  • Lysozyme enzyme in tears and saliva that kills bacteria
  • Hydrochloric acid in stomach that kills pathogens
• Lymphocytes


  Part of the immune system that helps protect the body by attacking pathogens
• Immune response to pathogens

  1. Each pathogen has unique antigens

  2. Lymphocyte with antibody that fits antigen is activated

  3. Activated lymphocytes divide to produce clones that produce lots of antibodies to destroy pathogen

  4. Some lymphocytes become memory cells ready to respond immediately if same antigen returns
• Antibodies


  Produced by white blood cells, specific to one particular kind of pathogen, can only destroy that kind of pathogen
• First infection


  Leads to production of memory lymphocytes
• Second infection


  Leads to faster, stronger immune response (secondary response)
• Pathogen


  An organism that causes disease
• Antigen


  Unique molecules on the surface of a pathogen
• Immune response


  1. Lymphocyte with matching antibody is activated

  2. Lymphocytes produce lots of antibodies

  3. Lymphocytes become memory lymphocytes
• Antibodies


  Molecules produced by lymphocytes that can only destroy one kind of pathogen
• Lymphocytes that do not have matching antibodies are not activated
• Lymphocyte activation


  Lymphocyte divides many times to produce clones
• First infection


  Immunity level increases
• Second infection


  Immunity level increases more rapidly (secondary response)
• Memory lymphocytes respond more quickly to another infection by the same pathogen
• Immunisation


  Giving a person a vaccine to prevent them becoming ill from a disease
• How vaccines work


  1. Vaccine contains antigens from pathogen

  2. Person's lymphocytes produce antibodies and memory lymphocytes

  3. Memory lymphocytes give rapid secondary response if infected
• The form of the pathogen in the vaccine is safe and cannot cause the disease