What is a microorganism?
single celled organism which cannot be seen without a microscope
What is a pathogen?
a microorganism which causes disease
What is a non-pathogenic organism?
a helpful organism which doesn’t cause disease
What is the definition of disease?
Malfunction of the body or which has an adverse effect on good health
What is an interface?
a boundary linking two systems. i.e. the external environment with the internal environment.
What are the three steps to a pathogen causing disease? And briefly explain each stage
1) Interface - gains entry
2) Colonise/Infection - multiplies in the hosts tissue
3) Disease - infection leads to recognisable symptoms, pathogen tries to resist defences and causes damage to the hosts tissue
Give three interfaces in which bacteria can gain entry
Skin
Gas Exchange System
Digestive System
Why is skin an effective barrier?
When does invasion of a pathogen usually occur between the skin interface and the internal environment?
Because it is a thick, continuous layer acting as an effective barrier
When cut or broken by an abrasion
Why is the gas exchange a good interface for pathogens to gain entry?
It is thin, moist and sticky in parts with a large surface area and well supplied with blood vessels so pathogens are able to easily enter.
What is meant by the word transmission?
When a pathogen is transferred from one individual to another
Give three examples of pathogens that gain entry through the gas exchange system
Tuberculosis, Influenza and bronchitis
Why is the digestive system a good interface for pathogens to gain entry?
It is thin and has a large surface area. Food and water which contains pathogens may be brought the stomach via the mouth meaning easy access into the body.
Give an example of a pathogen that gains entry through the digestive system
Vibrio Cholerae
Give four ways the bodies natural defences prevent a pathogen from gaining entry.
- a mucus layer covers the exchange surfaces and forms a sticky layer, making it difficult to penetrate
- the production of enzymes, which breaks down the pathogens
- cilia cells lining the trachea traps pathogens and moves it up into the mouth to then be swallowed
- production of HCl in the stomach kills the microorganism
Give six ways pathogens can be transmitted
Cuts (open wounds), droplets (sneezing), contact (contagious), sexual transmission (soft mucus membranes), food and water (egestion) and insects (injecting)
What are the two ways pathogens cause disease?
Producing toxins and damaging host tissue
Describe the different stages of how the influenza virus causes disease (from interface to colonisation to disease)
The influenza virus gains entry in the gas exchange system (direct horizontal contact)
It sticks to the epithelial cells, injects DNA into the cell. The DNA replicates by mitosis until the cell bursts and releases the new influenza virus to infect other cells.
Describe the different stages of how cholera causes diarrhoea (from interface to infection to disease)
Cholera gains entry into the digestive system via ingestion of dirty water (indirect transmission)
HCl kills some microorganisms, the rest survive and colonise in the tissue of the host. Attaches epithelial cell and causes Cl- ion channels to open so water lost through the lumen, causing diarrhoea
