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Infection and Response: Source: Seneca Learning - Coggle Diagram
Infection and Response:
Source: Seneca Learning
Communicable disease
Spreading disease
Pathogens and Infections:
Infections are caused whenever a foreign pathogen invades an organism (animal or plant). There are four main types of pathogen:
Viruses:
Viruses are tiny, non-living (do not contain cells) particles that can reproduce rapidly within the body.
They invade host cells and use them to make new virus particles.
Once the new viruses are made, they cause the cells to burst.
The cell damage makes us feel ill.
Viruses:
Viruses are tiny, non-living (do not have cells) particles that can reproduce rapidly within the body.
Invasion:
To survive and replicate, they invade host cells (animals or plant cells).
Replication:
The virus particle inserts its own DNA into the host cell’s DNA, which is then copied and used to make more viruses.
Invaded cells burst:
Once the new virus particles have been synthesised (made), they cause the cell to burst.
This releases the new viruses to invade more cells.
Illness:
This cell damage makes us feel ill.
Virus examples:
Many diseases are caused by viruses. Some examples are:
TMV (Tobacco mosaic virus):
Tobacco mosaic virus (TMV) is a pathogen that affects plants, such as tomatoes.
The unique ‘mosaic’ pattern of the discolouration of the plant stunts the growth of the affected plant, because photosynthesis cannot take place.
How do HIV and AIDS differ?:
AIDS (Acquired Immune Deficiency Syndrome) is caused by HIV (Human immunodeficiency virus).
It is the name given to the life-threatening infections that can occur when a person’s immune system has been badly damaged by HIV.
Measles:
Symptoms include a fever and red skin rash.
Measles is a virus that can be fatal if complications arise.
For this reason, most young children are vaccinated against measles.
The measles virus is spread by breathing in (inhaling) droplets from sneezes and coughs.
HIV (Human immunodeficiency virus):
HIV is spread by sexual contact or the exchange of body fluids (e.g blood from sharing needles).
Initially, HIV causes a flu-like illness. However, unless antiretroviral drugs are used successfully, the HIV virus enters the lymph nodes and attacks the body’s own immune cells.
AIDS is caused by HIV. It is the name given to the life-threatening infections that can happen when a person’s immune system has been badly damaged by HIV.
Bacteria:
Bacteria are small living cells that either damage cells directly or by producing toxins (poisons).
Bacteria can reproduce rapidly in the appropriate conditions: warm, moist areas with a good supply of oxygen.
The toxins released by bacteria can damage cells and tissues, making us feel ill.
Fungi:
Some fungi are single-celled organisms that have a body made up of hyphae (thread-like structures).
The hyphae are able to grow and penetrate tissues, such as human skin or the surface of plants.
The hyphae produce spores that can spread to other plants and animals.
Protists:
Protists are single-celled eukaryotic organisms (they have a nucleus).
Many are parasites, meaning that they live on or inside other organisms.
They are often transferred to the host organism by a vector, such as an insect or mosquito.
They make us feel ill by damaging our tissues.
Other Pathogens
Bacteria:
Bacteria are small living cells that either damage cells directly or by producing toxins (poisons).
Bacteria can reproduce rapidly in warm, moist conditions that have a good supply of oxygen.
Some examples of bacterial diseases:
Gonorrhoea:
Gonorrhoea is a sexually transmitted disease.
Its symptoms include pain when urinating and a thick yellow or green discharge from the vagina or penis.
Barrier methods of contraception, such as condoms, can be used to stop the bacteria spreading from person to person.
Salmonella:
If food has not been cooked properly or has been prepared in unhygienic conditions, then we may ingest (eat) Salmonella bacteria that cause food poisoning.
The bacteria release toxins (poisons), causing fever, stomach pain, vomiting and diarrhoea.
Fungi:
Fungi are unicellular (have one cell) or multicellular organisms that each have bodies made up of hyphae (thread-like structures).
The hyphae are able to grow and penetrate tissues, such as human skin or the surface of plants.
The hyphae produce spores that can spread to other plants and animals. An example of a fungal disease is:
Rose black spot:
Rose black spot can be spread in water or in the air (wind).
It causes purple or black spots on the leaves of rose plants.
Eventually, the leaves discolour and fall off. This makes it harder for plants to photosynthesise and plant growth slows.
Removing and destroying discoloured leaves and using fungicides can treat affected plants.
Protists:
Protists are single-celled eukaryotic organisms (they have a nucleus).
Lots of protists are parasites. This means that they live on or inside other organisms.
They are often transferred to the host organism by a vector, such as an insect or mosquito.
An example of a disease caused by a protist is:
Malaria:
Malaria is spread by the female anopheles mosquito (a vector).
If a mosquito is carrying malaria, then it transfers the infection into a person’s bloodstream when it bites them.
Malaria leads to recurring and severe fevers, which can cause death.
Spreading Disease:
There are three ways an infectious disease can spread:
Direct contact:
Some pathogens live on the surface of other organisms, such as the skin. If infected skin touches a surface, some of the pathogens can transfer from the infected skin to the surface.
The pathogen then spreads to other people who also touch that surface.
Athlete's foot
is spread in this way.
Water:
Some pathogens contaminate water supplies. Organisms drinking this contaminated water can be infected by pathogens.
Cholera
is a disease spread in this way.
Air:
Some pathogens are released into the air inside droplets when an organism coughs or sneezes. These droplets can then be inhaled (breathed in) by other organisms.
The
flu
and
common colds
are spread in this way.
Preventing infection spread:
The spread of infections can be prevented by being hygienic, by isolating infected individuals, by protecting against vectors and by vaccination.
Isolation:
By isolating infected individuals, we prevent contact with other organisms. This stops the infection from spreading.
Hygiene:
By being hygienic, we can destroy pathogens or wash them away so that they are not spread.
Using antibacterial products to clean surfaces, washing our hands and sneezing into a handkerchief are all hygienic measures to prevent the spread of infection.
Disease vectors:
Some protist diseases are carried by vectors.
A vector is an organism that carries pathogens without being infected.
For example, we can protect against mosquitos carrying malaria using mosquito nets.
Vaccination:
Vaccination can make people immune to (resistant to) infection.
The more individuals that are vaccinated, the less likely the disease is to spread.
Human Defence Systems
Non - Specific Defences:
The human body has non-specific defences. They are designed to prevent any pathogens from entering the body and causing harm.
Tears:
Tears contain enzymes that destroy any pathogens that make contact with our eye.
Stomach acid:
Glands in the stomach wall produce hydrochloric acid, which destroys any pathogens that enter the stomach.
Mucus:
Mucus is produced in the respiratory system and traps the particles and bacteria entering our airways.
Skin:
Skin is a waterproof barrier that pathogens cannot pass through.
Good bacteria live permanently on our skin, covering the surface and preventing pathogens from growing on our skin.
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The Immune System:
If a pathogen passes the non-specific defences, the immune system is activated. The immune system is made up of different white blood cells, which have different functions.
Antitoxins:
Some bacteria produce toxins that can damage cells and tissues.
The immune system responds to this by producing antitoxins, which neutralise the toxins released by the bacteria and prevent them from causing harm.
Antibodies:
White blood cells recognise foreign antigens (proteins) on the surface of pathogens and produce protein molecules called antibodies.
Antibodies are specific to particular pathogens.
Phagocytosis:
A white blood cell finds the pathogen and engulfs it by changing shape.
The white blood cell ingests (absorbs) and digests the pathogen, destroying it.