Non specific response AQA overview

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  • Created by: melvin
  • Created on: 28-04-12 11:42

non specific response

this is the bodies natural defneces and barriers stoping pathogens entering the body. They are all part of the respiratory, digestive and system, as well as your skin and eyes. All of these contain many different mechanisms that attack any foreign bodies that manage to get there.

It usually consists of either a physical, chemical, or in the case of phagocytosis, cellular response that prevents microbes entering your body. These defenses are present from birth and provide a quick and effective response against a large number of foreign substances.

It must be noted that this response does not distinguish between different pathogens and attacks all foreign bodies.

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Respiratory system

Contains the following as a form of primary response

- mucus

- Phagocytes

- cilia

- presence of antibodies

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Digestive system

the stomach has the following barriers

- presence of lysozymes

- very low pH

- presence of flora*

*flora is the huge number of bacterial cells that live in your gut. the huge number of them make it difficult for pathogens to survive as competition is high and space is small.

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skin and eyes

On your skin, you have:

- sweat containing sebum

- the secretion of fatty acids creating a low pH

- commensal microbes that make it difficult for other microbes to survive on your skin

And in your eyes:

- lysozymes in tears

- washing action of tears

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inflammations and phagocytosis

Inflammations are a primary response that happense when a foreign substance enters the skin. It itself does not destroy the pathogen, but induces phagocytes to go to to the area and destroy all the foreign bodies at the point of entering.

1) Mast cells release histamines. these cause the area to swell, burn up, or become inflammed. The point of this is to increase blood to be routed to the area.

2) the histamines do a few things after this. This is dependent on what receptors binds to the histamine. In order of the receptors Hn:

H1 - the body becoming more alert and awake and inflammation or hives

H2- muscles relaxing, release of gastric acid

H3 - mast cells stop producing histamines

H4 - opens up capillaries, making them leak, allowing white blood cells to be released

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Inflammation (cont.)

3) Platelets are then released. these cause the the capillaries to seal again.

4) Cytokines are then produced. But this only happens when a virus enters the body. these are proteins that stop viruses reprducing.

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Phagocytosis is the ingestion of a pathogen by a phagocyte known as a macrophage. There are 4 main other types of phagocytes despite this.

There are neutrophils, which do phagocytosis but viciously and quickly. They also destroy cells that are damaged or coated in antibodies.

Monocytes are phagocytes which become antigen presenting cells, or macrophages or dendritic cells. 

There are dendritic cells which have long outgrowths (like dendrites on a nereve cell) which allow it to have a large surface area used for ingesting pathogens.

Macrophages are like garbage collectors, or violenta and even bigger neutrophils.

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Phagocytosis (cont.)

The 4 main steps of phagocytosis (according to the mark scheme)

1) Phagocytes engulf pathogen/microoganism

2) Encolses it insed a vesicle called a phaogosome

3) Lysosomes present inside phagocyte which contain lytic enzymes.

4) These digest the pathogen in the phagosome by breaking down their cell walls and hydrolysing molecules inside. ultimately killing it.

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