Diseases

(GCSE Content)

      Communicable and non-communicable diseases. Communicable diseases are diseases which can be spread from person to person, non-communicable therefore cannot be spread person to person

        Communicable diseases are caused by pathogens (microorganisms that cause disease) and can be passed from person to person by a number of things; exchange of body fluids (e.g blood, skin, STDs and STIs, Pregnancy through the placenta), vectors (an animal or insect that causes disease) , through the air, food and water ingested.

Sick Saturday;literally (Kelly Sikkema)

        Pathogens can come in four forms; bacteria, fungi, viruses and protists;

•         Bacteria are unicellular organisms that can cause disease (note: not all are harmful). They are smaller than average plant and animal cells but larger than protists and viruses. They produce very quickly using binary fission and can produced toxins in the body which can damage and kill body cells. The body produces antitoxins to neutralise and counteract these toxins. Additionally, see phagocytosis in how the body kills harmful bacteria. We can also take antibiotics which can kill the bacteria.

•      Viruses are smaller, not alive microorganisms which can also cause disease by reproducing inside and therefore damaging/ killing host cells from within. Viruses are harder to get rid of because they are not alive therefore we cannot kill them. Viral diseases like HIV and AIDS cannot be cured but merely controlled to help them progress less using antiviral medication.

        Phagocytosis is the process of the phagocyte (white blood cells) engulfing and breaking down the pathogens in the body. Firstly, the white blood cells can detect a pathogen as its antigen markers on its surface don’t match the bodies. This cell then flags this up and other white blood cells come to this part of the body. The white blood cells then produce specific antibodies to match this specific pathogen which the attach to these antigen markers. The phagocytes then engulf and digest (using enzymes to break down) any pathogens with these antibodies on.

   Memory cells in the body help to ‘remember’ the specific antibodies required to each pathogen which means that if this pathogen enters the body again, the body can trigger a faster immune response- less or no symptoms

       Vaccinations work in a similar way, they are injections of dead or inactive pathogens meaning your body still can produce the correct antibodies without you getting sick. The memory cells then can ‘remember’ what antibodies are needed and if you are to become infected, the immune response is very fast and efficient.

•          Protists are microscopic organisms that are neither bacterium, virus or fungus. Malaria is a type of protist caused disease. Four points about malaria;

-It is spread from person to person via the anopheles’ female mosquito

-The protist damages blood cells and the liver and symptoms include vomiting, headaches

-This can be prevented using mosquito nets and insecticides

-It can be treated if caught early enough with antimalarial drugs- but if too late it can result in death.

       There are many human defences against disease; there are enzymes and antimicrobials in our tears, hairs and mucus in the nasal passage to trap pathogens and move the pathogens out of them, mucus and cilia in the trachea to sweep pathogens out, skin surface secretes antimicrobial chemicals and is another protective layer, stomach acid low Ph to kill pathogens

       Herd immunity is the idea that the more people vaccinated from a disease the less the disease can spread in a population.