INFECTION AND RESPONSE J

• Communicable disease - can easily spread from person to person 
• Pathogens are microorganisms that enter the body and cause disease , they are communicable. Both animals and plants can be infected by pathogens 
• Pathogens can be bacteria , viruses , protists or fungi 
• Bacteria - very small living cells : can reproduced rapidly inside your body. Can make you feel ill by producing toxins that damage your cells and tissues. 
• Viruses are not cells - they are much smaller 

  • they can reproduce rapidly inside your body 
  • They live inside your cells and replicate themselves using the cells machinery to produce copies of themselves 
  • The cell will usually then burst releasing all the new viruses 
  • This cell damage is what makes you feel ill 
• Protists are single celled eukaryotes 

  • some protists are parasites and live on or inside other organisms and can cause them damage. They are often transferred by a vector 
• Fungi come in different shapes

  • hyphae can grow and penetrate human skin.
• Pathogens can be spread by drinking or bathing in contaminated water eg cholera 
• Pathogens can be spread by the air and can then be breathed in. Droplets from when you cough and sneeze are in the air. Eg influenza virus 
• Pathogens can be spread by direct contact eg touching contaminated surfaces , including skin. Eg athletes foot.
• Measles is a viral disease 
• Measles is spread by droplets from an infected persons sneeze or cough. In uk most people are vaccinated against it when they were younger.

  Symptoms :  red rash , fever 

  Measles can be very serious if there are complications and could lead to brain infections. 
• HIV is a virus spread by sexual contact or exchanging bodily fluids such as blood. This can happen when people share needles.

  Symptoms : initially symptoms are flu like for a few weeks and then they will feel better but really damage is worsening. If bodies immune system is badly damages they won’t be able to cope with other diseases and so have developed aids.  

  Treatment : ant-retrieval drugs prevent virus from replicating 
• TMV affects many species of plants 

  Symptoms : causes a mosaic pattern on the leaves of plants and parts of leaves become discoloured 

  Discolouration means plants cannot carry out photosynthesis as so virus affects growth. 
• Rose black spot is a fungal disease 
• Symptoms of Rose black spot :causes black spots to develop on the leaves of plants. The leaves can then become yellow and drop off. Means less photosynthesis and lack of growth. 

  Rose black spot spreads through the environment in water or by the wind. 

  Treatment : use fungicides or cut of infected part of plant , the leaves need to then be destroyed so they don’t affect other plants 
• Malaria is a disease caused by a protist 
• mosquitoes are vectors , they pick up the malarial protist when they feed on an infected animal. Every time that mosquito feed on another animal it infects it . 

  Symptoms : repeating episodes of fever 

  Treatment : mosquito repellent , mosquito nets , destroy their habitat 
• Salmonella is a bacterial disease that causes food poisoning 
• Salmonella symptoms : fever , stomach cramps , vomiting , diarrhoea 

  Symptoms are caused by toxins produced by bacteria 

  You can get salmonella from raw chicken or from eating a chicken that was infected with disease whilst alive 
• Gonorrhoea is a bacteria disease spread through sexual contact 

  Symptoms : pain when urinating , thick yellow or green discharge from penis or vagina.

  Treatment : originally treated with antibiotic penicillin but strains of bacteria have become resistant to it . Now we encourage barrier methods of contraception and different types of antibiotics. 
• Being hygienic - can prevent spread of disease eg washing hands 
• Destroying vectors can prevent disease, getting rid of organisms that spread disease can prevent further spreading of disease eg spread of malaria can be stopped by stopping mosquito breeding 
• Isolating infected individuals- isolate someone with a communicable disease as it prevent them from spreading it to someone else 
• Vaccination - means they cannot develop infection or pass it onto anyone else 
• Defence systems - skin is a physical barrier. It also secretes antimicrobial substance which kill pathogens 
• Hair and mucus in your nose trap particles that could contain pathogens 
• Trachea and bronchi secrete mucus to trap pathogens. They are also lined with cilia which are hair like structures that waft mucus to the back of the throat where it can be swallowed. 
• Stomach produces hydrochloric acid. This kills pathogens that make it that far from mouth. 
• Immune system attacks pathogens and destroys them. Most important part of immune system is white blood cells.  
• White blood cells can engulf pathogens and digest them ( phagocytosis ) 
• White blood cells produce antibodies. Antibodies are small proteins produced by white blood cells and bind to specific antigens. They act as a signal to our immune system to destroy the antigen. If person is affected with the same pathogen again the white blood cells will rapidly produce antibodies. 
• White blood cells produce anti toxins , these counteract toxins produced by bacteria. 
• Vaccination - protects from future infections
• Vaccines involve injecting small amounts of dead or inactive pathogens. These carry antigens which cause your body to create antibodies to attack them even though the pathogen is harmless. But if this pathogen was to appear again the white blood cells can rapidly mass produce antibodies to kill off pathogen. 
• Pros of vaccines - controls communicable diseases that were once very common , prevent huge outbreaks of disease ( epidemics ) eg covid 19 
• Cons of vaccines - they don’t always work , don’t give you full immunity , sometime you can have a bad reaction ( seizures and fever are very rare )
• Herd immunity - indirect protection from a disease as most of the population is already vaccinated. 
• Some drugs relieve pain and some solve the problem 
• Relief - painkillers , aspirin 

  Treat disease - antibiotics