Diseases can either be single factor (have a single cause) or multifactorial (many causes.
Can be classed as communicable or non-communicable
Communicable- infectious diseases such as; Malaria, Influenza, Cholera, Tuberculosis, HIV/AIDS
Non-communicable include diabetes, arthritis, lung cancer scurvy, emphysema not caused by pathogens and non-infectious.
Lifestyles affecting human health- smoking, poor diet, lack of exercise, alcohol, stress
A pathogen is a disease causing organism.
Fungi- Eukaryotic e.g. athlete’s foot
Bacteria- Prokaryotic e.g. TB
Virus- Akaryotic e.g. HIV
Pathogens can be transmitted by direct contact, airborne, waterborne, food, insects and animals
Pathogens cause disease by producing toxins and damaging cells.
This is a serious water borne and food borne bacterial infection
Sufferer suffers from dehydration and diarrhoea.
A toxic protein is released by the cholera bacteria into the small intestine.
Toxin damages the carrier proteins in the plasma membrane of the epithelial cells lining the small intestine.
This produces a large release of chloride ions into the gut lumen.
This decreases the water potential of the gut
The water potential gradient causes the intestinal cells to lose large amounts of water into the gut lumen
Oral rehydration solutions contain sodium glucose and water.
Increases uptake of sodium and glucose into the epithelial cells by making use of the sodium-glucose co-transport proteins.
Lowers the water potential inside the cells
Water following from the lumen by osmosis
For- may be faster relief from symptoms, may benefit others later
Against- may be less effective than previous, cost
Defence against disease
Lysosome enzyme in tear
Cilia and mucus in trachea
Sweat glands in skin
Acidic pH of stomach
There immune system is divided into non-specific and specific response.
Non-specific- is always the same and is effective against a wide range of pathogens and substances considered non-self.
Phagocytosis is the term used to describe how a phagocyte engulfs a foreign substance.
1. Phagocyte engulfs pathogens
2. They are enclosed in a vacuole
3. This vacuole fuses with lysosomes
4. Lysosomes contain hydrolytic enzymes
5. These hydrolyse the pathogen
The phagocyte places antigens from the pathogen on its cell surface to become an antigen presenting cell, i.e. let other cells know.
The specific immune response is brought about by white blood cells called lymphocytes. The response is specific because each lymphocyte only recognises one antigen.
An antigen is a protein on a cell membrane causing an immune response, involving antibodies.
An antibody is a protein produced by a B cell in response to a particular antigen. It combines with the antigen forming an antigen-antibody complex and causes it to be destroyed.
The cell mediated response
1. Pathogens invade body cells
2. Phagocyte places antigens from the pathogen on its surface
3. Receptors on certain specific T helper cells fit exactly into these antigens
4. T cells divide rapidly by mitosis to form clones
5. Cloned T cells; kill infected body cells, develop into memory cells for future infections
The humoral response
1. Involves B cells and antibody production
2. The cell surfaces of B cells contains receptors which bind to non- self antigens
3. Specific lymphocyte with complementary receptor attaches to antigen
4. Divides rapidly by mitosis to give a clone and identical lymphocytes.
5. Cloned cells become plasma cells which secrete antibodies that destroy pathogens
6. Or produce large numbers