biology - infection and response

• Communicable diseases


  Diseases that can be spread from person to person or between animals and people
• Non-communicable diseases


  Diseases that cannot spread from person to person or between animals and people. They generally last for a long time and get worse slowly
• Communicable diseases


  • Measles
  • Malaria
• Non-communicable diseases


  • Asthma
  • Cancer
  • Coronary heart disease
• Health


  The state of physical and mental well-being
• Issues affecting mental or physical well-being


  • Diet
  • Stress
  • Life situations
• Pathogen


  A microorganism that can cause disease when it infects its host
• Risk factor


  Something that increases your chance of getting a disease
• Diseases interacting


  • Problems in the immune system means that an individual is more likely to suffer from infectious diseases
  • Viruses living in cells can be triggers for cancers
  • Immune reactions caused by a pathogen can trigger allergies such as asthma and skin rashes
  • Severe physical ill health can lead to mental health issues such as depression
• Risk factors that can directly cause disease


  • Smoking can directly cause lung cancer, cardiovascular disease and lung diseases
  • Obesity can directly cause type 2 diabetes
  • Drinking too much alcohol can directly cause liver disease
  • Smoking and drinking while pregnant can damage the health of the growing foetus
  • Carcinogens such as ionising radiation as a risk factor for cancer
• Ionising radiation


  An example is x-rays or exposure to UV rays
• Cancer


  Caused by uncontrolled cell growth and divisions
• Benign tumor


  An abnormal growth of cells confined to one area normally within a membrane. They don't invade other parts of the body
• Malignant tumor


  Malignant tumor cells are cancers. They invade neighboring tissues and spread to other parts of the body in the blood where they form secondary tumors. Cells can break off and spread to other parts of the body in the blood
• Genetic risk factors for cancer


  • Inheriting faulty genes makes you more susceptible to cancer
  • Mutations in the BRCA genes have been linked to an increased likelihood of getting breast or ovarian cancer
• Pathogen


  Microorganisms that can enter the body and cause disease. They cause communicable diseases that easily spread. Both plants and animals can be infected by pathogens
• Bacteria


  Very small cells (100th the size of your body cells) which can rapidly reproduce inside your body. They make you feel ill by producing toxins that damage cells and tissues
• Viruses


  Not cells, much smaller and about 1/100th size of a bacterium. Like bacteria they can reproduce rapidly inside your body. They live inside cells and replicate themselves using the cells' machinery to produce many copies of themselves. The cell damage is what makes you feel ill
• Protists


  All eukaryotes and most of them are single celled. Some protists are parasites that live on or inside other organisms and can cause them damage. They are often transferred to the organism by a vector that doesn't get the disease itself
• Fungi


  Some are single celled, others have a body made up of hyphae (thread like structures) that can grow and penetrate human skin and the surface of plants causing diseases. These hyphae can produce spores which can spread to other plants and animals
• Ways pathogens can spread


  • Water
  • Air
  • Direct contact
• Measles


  A viral disease spread by droplets from an infected person's cough or cold. People with measles develop a skin rash and fever. It can be dangerous or fatal if there are complications and can lead to pneumonia. Most people are vaccinated against measles when they are young
• HIV


  Spread by sexual contact or by exchanging bodily fluids such as blood, e.g. when people share needles when taking drugs
• HIV symptoms


  It normally starts off as flu-like symptoms for a few weeks. Usually the person then doesn't experience any symptoms for a few years. During this time, HIV can be controlled with antiretroviral drugs. These stops the virus replicating in your body
• Late HIV/AIDS


  If the body's immune system is badly damaged it can't cope with other infections such as Cancer
• Tobacco mosaic virus (TMV)


  A virus that affects many species of plant e.g. tomatoes. It causes a mosaic pattern on the leaves of the plant - these parts of leaves become discoloured. This means the plant can't carry photosynthesis out as well so TMV affects growth
• Rose black spot disease


  A fungal disease that causes purple or black spots to develop on the leaves of rose plants. The leaves can then turn yellow and drop off, meaning less photosynthesis can happen so the plant doesn't grow very well
• How rose black spot disease spreads

  In water, or by the wind
• How gardeners treat rose black spot


  Using fungicides and by stripping the plant of its affected leaves. These leaves then need to be destroyed so that the fungus can't spread to other plants
• Malaria


  Caused by a protist. Part of the malarial protist's life cycle takes place in a mosquito, which is a vector that carries the disease without being affected and picks it up when they feed on an infected animal. It causes repeated episodes of fever and can be fatal
• Preventing malaria


  People can be protected from mosquitoes using insecticides and mosquito nets
• Salmonella


  A type of bacteria that causes food poisoning, with symptoms of fever, stomach cramps, vomiting and diarrhoea caused by the toxins produced by the bacteria. It is contracted by eating food contaminated with salmonella bacteria
• Gonorrhoea


  A sexually transmitted disease (STD) caused by bacteria. It will be painful to urinate, with another symptom being thick yellow or green discharge from the vagina or penis
• Preventing the spread of STDs


  People could be treated with antibiotics and should use barrier methods of contraception such as condoms
• Ways to reduce and prevent the spread of disease


  • Being hygienic
  • Destroying vectors (organisms that spread disease)
  • Isolating infected individuals
  • Vaccination
• How the skin prevents pathogens


  It acts as a barrier against pathogens and secretes antimicrobial substances which kill pathogens
• How the nose prevents pathogens


  Hairs and mucus in your nose trap particles that could contain pathogens
• How the trachea and bronchi prevent pathogens


  They secrete mucus to trap pathogens, and are lined with cilia (hair-like structures) which waft the mucus up to the back of the throat where it can be swallowed
• How the stomach prevents pathogens


  It produces hydrochloric acid which kills pathogens which make it far from the mouth
• The immune system


  Deals with pathogens that enter the body