What is a pathogen
Disease causing organism
What are transmissible diseases
• Pathogens are passed on from one host to another
Mechanical barriers
structures that make it difficult for pathogens to get past them and into the body
Examples of mechanical barriers and the uses
a) Skin - covers almost all parts of your body to prevent infection from pathogens.
b) Hairs in the nose - make it difficult for pathogens to get past them further up the nose so they not inhaled into the lungs
Whats chemical barrier
substances produced by body cells that trap / kill pathogens before they can get further into the body and cause disease
Examples of chemical barrier
a) Mucus - pathogens get trapped in the mucus and can then be removed from the body
b) Stomach acid - hydrochloric acid which is strong enough to kill any pathogens
Cells
different types of white blood cell work to prevent pathogens reaching areas of the body they can replicate it
Phagocytosis
engulfing and digesting pathogenic cells
Pathogens can be killed other than phagocytosis by
producing antibodies - which clump pathogenic cells together so they can’t move as easily (known as agglutination) and releasing chemicals that signal to other cells that they must be destroyed
What is active immunity
Making antibodies and developing memory cells for future response to infection
Two ways active immunity occurs
• The body has become infected with a pathogen so lymphocytes go through the process of making antibodies specific to that pathogen
• Vaccination
What ability does lymphocytes have
‘read’ antigens on the surfaces of cells and recognize any that are foreign
They then make antibodies which are a complementary shape to the antigens on the surface of the pathogenic cells
What do vaccinations give
Protection against specific diseases and boosts the bodys defense against infection from pathogens
What is passive immunity
ast-acting, short-term defence against a pathogen by antibodies acquired from another individual
Examples of passive immunity
• Antibodies pass from mother to infant from breast milk - it helps very young to fight off infections until they are older and stronger and their immune system is more responsive
How does Vibrio cholerae cause diarrhoea?
- Bacteria attach to wall of small intestine
- produce a toxin
- toxin stimulates cells lining the intestine to release chloride ions from inside cells into lumen of intestine
- chloride ions accumulate in lumen of small intestine and lower water potential there
- Once water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis)
- Large quantities of water are lost from the body in watery faeces
- The blood contains too little chloride ions and water
