Infection and Response
Communicable disease
Communicable Disease:
- Pathogens are microorganisms that enter the body and cause disease. They cause Viral diseases
communicable diseases that can easily spread. There are 4 types of pathogens Bacterial diseases
o Bacteria – tiny living cells which can reproduce rapidly inside your body. They
Fungal diseases
can make you feel ill by producing toxins that damage your cells and tissues.
o Viruses – not cells, they are much smaller than bacteria. Like bacteria, they Protist diseases
can reproduce rapidly inside your body. They live inside your cells and Human defence systems
replicate themselves using the cell’s machinery to produce many copies of
Vaccination
themselves – the cell will usually burst, releasing all the new viruses. Cell
damage makes you feel ill. Antibiotics
o Protists – single-celled eukaryotes. Some protists are parasites that live on Drug testing
or inside other organisms and can cause them damage, often transferred to Monoclonal antibodies
the organism by a vector, which doesn’t get the disease itself
Plant diseases
o Fungi – come in different shapes – some are single-celled. Others have a
body made of hyphae (thread-like structures), which can grow and Plant defences
penetrate human skin and plant surfaces, causing diseases. It can also produce spores, spread
to other organisms.
- Pathogens can be spread in different ways:
o Water – some pathogens can be picked up by drinking/bathing in dirty water.
o Airborne pathogens can be carried in the air and then inhaled. Some airborne pathogens are
carried in the air in droplets produced when you cough or sneeze.
o Direct contact – some pathogens can be picked up by touching contaminated surfaces,
including skin.
Viral Diseases:
- Measles are a highly contagious viral disease usually transmitted between young children. It is spread by
droplets from an infected person’s sneeze or cough. Symptoms include a fever and a red skin rash.
Most people are vaccinated against measles when they’re young. Measles can be very serious, or even
fatal, if there are complications. Can lead to pneumonia, sterility in adults and foetal abnormalities.
- HIV stands for human immunodeficiency virus. It is transmitted when body fluids are shared, usually
during sex. Immediately after infection, the symptoms appear as a flu-like illness. After this, infected
people usually show no symptoms. A lot of people don’t even notice they’re infected. During this time,
HIV can be controlled with antiretroviral drugs, which stop the virus from replicating in the body. The
virus attacks the immune cells. If the body’s immune system is badly damaged, it can’t cope with other
infections or cancers. At this stage, it is known as AIDS.
Bacterial Diseases:
- Salmonella is a type of bacteria that causes food poisoning. You can get salmonella food poisoning by
eating food that’s been contaminated with salmonella bacteria. E.g. eating chicken that caught the
disease whilst it was alive or eating food that has been contaminated by being prepared in unhygienic
conditions. In the UK, most poultry are given a vaccination against Salmonella. This is to control the
spread of the disease.
- Gonorrhoea is an STD which is passed on by sexual contact. A person with gonorrhoea will get pain
when they urinate. Another symptom is a thick yellow or green discharge. It was originally treated with
an antibiotic called penicillin, but this has become harder now because strains of the bacteria have
1
, become resistant to it. To prevent the spread of gonorrhoea, people can be treated with antibiotics and
should use barrier methods of contraception.
Fungal Diseases:
- Athlete’s foot is a fungal infection of people’s feet that causes itching, flaking and blistering. It is
transmitted in communal areas where people walk barefoot, such as swimming pools and changing
rooms. Infection can be treated by keeping feet dry and applying an antifungal cream or spray.
Protist Diseases:
- Malaria is a disease caused by protists. Symptoms include fever, tiredness, vomiting and headaches. The
pathogens are transferred between people by mosquitoes. Malaria causes repeated episodes of fever. It
can be fatal the spread of malaria can be reducing by stopping mosquitos from breeding. People can be
protected from mosquitoes using insecticides and mosquito nets.
Human Defence Systems:
- The first line of defence
o Your body’s natural barriers to infection include your skin, lysozymes in tears and saliva, which
are antibacterial enzymes, hairs and cilia, and stomach acid.
- The second line of defence
o Phagocytes are a type of white blood cell. They engulf pathogens, as well as your own dead or
dying cells. When a phagocyte comes into contact with a pathogen, it binds to it. The
membrane of the phagocyte then surrounds the pathogen and absorbs it into a vacuole within
its cytoplasm. Here, enzymes are added to the vacuole to break down the pathogen. This is
called phagocytosis.
- Third line of defence
o Lymphocytes are a second type of white blood cell. Almost all cells have proteins called
antigens on their surface. Pathogens have different antigens from those found in your cells.
Your lymphocytes recognise the foreign antigens present on invading pathogens. They produce
large numbers of antibodies. This takes several days; the antibodies are specific for the antigen
present on the pathogen, which means the shape of the antibody fits perfectly with the
shape of the antigen. Antibodies help clump pathogens together so that they can then be
engulfed and destroyed by phagocytes more easily.
o If you are infected a second time with the same pathogen, your lymphocytes will recognise its
antigens and be able to produce larger numbers of antibodies more quickly. WE call these white
blood cells ‘memory’ lymphocytes. This is likely to mean you won’t fall ill from the same
pathogen twice.
o Many pathogens produce toxins that also make you ill. To defend against these specific toxins,
your lymphocytes can produce a special type of antibody called an antitoxin. This will bind with
and neutralise the toxin, helping you feel better.
Vaccination:
- A vaccination is the deliberate exposure to antigenic material.
- The vaccine that is injected contains a small amount of the weakened pathogen or even a dead version
of the pathogen.
- Although the antigens which are injected into you are weakened, it is still a pathogen. Therefore, in the
day or two it takes the immune system to overcome the pathogen, you will feel a little under the
weather.
2
Communicable disease
Communicable Disease:
- Pathogens are microorganisms that enter the body and cause disease. They cause Viral diseases
communicable diseases that can easily spread. There are 4 types of pathogens Bacterial diseases
o Bacteria – tiny living cells which can reproduce rapidly inside your body. They
Fungal diseases
can make you feel ill by producing toxins that damage your cells and tissues.
o Viruses – not cells, they are much smaller than bacteria. Like bacteria, they Protist diseases
can reproduce rapidly inside your body. They live inside your cells and Human defence systems
replicate themselves using the cell’s machinery to produce many copies of
Vaccination
themselves – the cell will usually burst, releasing all the new viruses. Cell
damage makes you feel ill. Antibiotics
o Protists – single-celled eukaryotes. Some protists are parasites that live on Drug testing
or inside other organisms and can cause them damage, often transferred to Monoclonal antibodies
the organism by a vector, which doesn’t get the disease itself
Plant diseases
o Fungi – come in different shapes – some are single-celled. Others have a
body made of hyphae (thread-like structures), which can grow and Plant defences
penetrate human skin and plant surfaces, causing diseases. It can also produce spores, spread
to other organisms.
- Pathogens can be spread in different ways:
o Water – some pathogens can be picked up by drinking/bathing in dirty water.
o Airborne pathogens can be carried in the air and then inhaled. Some airborne pathogens are
carried in the air in droplets produced when you cough or sneeze.
o Direct contact – some pathogens can be picked up by touching contaminated surfaces,
including skin.
Viral Diseases:
- Measles are a highly contagious viral disease usually transmitted between young children. It is spread by
droplets from an infected person’s sneeze or cough. Symptoms include a fever and a red skin rash.
Most people are vaccinated against measles when they’re young. Measles can be very serious, or even
fatal, if there are complications. Can lead to pneumonia, sterility in adults and foetal abnormalities.
- HIV stands for human immunodeficiency virus. It is transmitted when body fluids are shared, usually
during sex. Immediately after infection, the symptoms appear as a flu-like illness. After this, infected
people usually show no symptoms. A lot of people don’t even notice they’re infected. During this time,
HIV can be controlled with antiretroviral drugs, which stop the virus from replicating in the body. The
virus attacks the immune cells. If the body’s immune system is badly damaged, it can’t cope with other
infections or cancers. At this stage, it is known as AIDS.
Bacterial Diseases:
- Salmonella is a type of bacteria that causes food poisoning. You can get salmonella food poisoning by
eating food that’s been contaminated with salmonella bacteria. E.g. eating chicken that caught the
disease whilst it was alive or eating food that has been contaminated by being prepared in unhygienic
conditions. In the UK, most poultry are given a vaccination against Salmonella. This is to control the
spread of the disease.
- Gonorrhoea is an STD which is passed on by sexual contact. A person with gonorrhoea will get pain
when they urinate. Another symptom is a thick yellow or green discharge. It was originally treated with
an antibiotic called penicillin, but this has become harder now because strains of the bacteria have
1
, become resistant to it. To prevent the spread of gonorrhoea, people can be treated with antibiotics and
should use barrier methods of contraception.
Fungal Diseases:
- Athlete’s foot is a fungal infection of people’s feet that causes itching, flaking and blistering. It is
transmitted in communal areas where people walk barefoot, such as swimming pools and changing
rooms. Infection can be treated by keeping feet dry and applying an antifungal cream or spray.
Protist Diseases:
- Malaria is a disease caused by protists. Symptoms include fever, tiredness, vomiting and headaches. The
pathogens are transferred between people by mosquitoes. Malaria causes repeated episodes of fever. It
can be fatal the spread of malaria can be reducing by stopping mosquitos from breeding. People can be
protected from mosquitoes using insecticides and mosquito nets.
Human Defence Systems:
- The first line of defence
o Your body’s natural barriers to infection include your skin, lysozymes in tears and saliva, which
are antibacterial enzymes, hairs and cilia, and stomach acid.
- The second line of defence
o Phagocytes are a type of white blood cell. They engulf pathogens, as well as your own dead or
dying cells. When a phagocyte comes into contact with a pathogen, it binds to it. The
membrane of the phagocyte then surrounds the pathogen and absorbs it into a vacuole within
its cytoplasm. Here, enzymes are added to the vacuole to break down the pathogen. This is
called phagocytosis.
- Third line of defence
o Lymphocytes are a second type of white blood cell. Almost all cells have proteins called
antigens on their surface. Pathogens have different antigens from those found in your cells.
Your lymphocytes recognise the foreign antigens present on invading pathogens. They produce
large numbers of antibodies. This takes several days; the antibodies are specific for the antigen
present on the pathogen, which means the shape of the antibody fits perfectly with the
shape of the antigen. Antibodies help clump pathogens together so that they can then be
engulfed and destroyed by phagocytes more easily.
o If you are infected a second time with the same pathogen, your lymphocytes will recognise its
antigens and be able to produce larger numbers of antibodies more quickly. WE call these white
blood cells ‘memory’ lymphocytes. This is likely to mean you won’t fall ill from the same
pathogen twice.
o Many pathogens produce toxins that also make you ill. To defend against these specific toxins,
your lymphocytes can produce a special type of antibody called an antitoxin. This will bind with
and neutralise the toxin, helping you feel better.
Vaccination:
- A vaccination is the deliberate exposure to antigenic material.
- The vaccine that is injected contains a small amount of the weakened pathogen or even a dead version
of the pathogen.
- Although the antigens which are injected into you are weakened, it is still a pathogen. Therefore, in the
day or two it takes the immune system to overcome the pathogen, you will feel a little under the
weather.
2
