Communicable diseases, disease prevention and the immune system Flashcards
(102 cards)
1
Q
What type of pathogen is responsible for Tuberculosis (TB)?
A
Bacterium
2
Q
What does TB affect?
A
Animals typically humans and cattle
3
Q
What type of pathogen is responsible for Malaria?
A
Protoctist
4
Q
What does malaria affect?
A
Animals including humans
5
Q
What type of pathogen is responsible for HIV/AIDS?
A
Virus
6
Q
What does HIV/AIDS affect?
A
Humans
7
Q
What type of pathogen is responsible for ring rot?
A
Bacterium
8
Q
What does ring rot affect?
A
Potatoes and tomatoes
9
Q
What type of pathogen is responsible for ringworm?
A
Fungus
10
Q
What does ringworm affect?
A
Cattle
11
Q
What type of pathogen is responsible for Tobacco mosaic virus?
A
Virus
12
Q
What does tobacco mosaic virus affect?
A
Plants
13
Q
What type of pathogen is responsible for Potato/ tomato late blight?
A
Protoctist
14
Q
What type of pathogen is responsible for athletes foot?
A
Fungus
15
Q
What does athletes foot affect?
A
Humans
16
Q
What type of pathogen is responsible for Bacterial meningitis?
A
Bacterium
17
Q
What does bacterial meningitis affect?
A
Humans
18
Q
What type of pathogen is responsible for influenza ?
A
Virus
19
Q
What does influenza affect?
A
Animals, including humans
20
Q
What type of pathogen is responsible for Black sigatoka?
A
Fungus
21
Q
What does black sigatoka affect?
A
Banana plants
22
Q
What is a communicable disease?
A
A disease that can be spread between organisms
23
Q
What is direct transmission?
A
When a disease is transmitted directly from one organism to another. Direct transmission can happen in several ways, including: droplet infection (coughing and sneezing tiny droplets of mucus or saliva directly onto someone), sexual intercourse, or touching an infected organism
24
Q
What is indirect transmission?
A
When a disease is transmitted from one organism to another via an intermediate. Intermediates include air, water, food or another organism (known as a vector).
25
Examples of direct transmission?
HIV can be transmitted directly between humans via sexual intercourse.
Athlete's food can be spread via touch.
26
Examples of indirect transmission?
Potato/ tomato late blight is spread when spores are carried between plants- first in the air, and then in water.
Malaria is spread between humans (and other animals) by mosquitoes- insects that feed on blood. The mosquitoes act as vectors- they don't cause malaria themselves, they just spread the protoctista that cause it.
27
Example of how overcrowding living conditions increase the transmission of many communicable diseases?
TB is spread directly via droplet infection. It's also spread indirectly because the bacteria can remian in the air for long periods of time and infect new people. The risk of TB is increased when lots of people live crowded together in a small space.
28
Example of how climate can increase the transmission of many communicable diseases?
- Potato/ tomato late blight is especially common during wet summers because the spores need water to spread.
- Malaria is most common in tropical countries, which are humid and hot. This is because these are ideal conditions for mosquitoes (the malaria vectors) to breed.
29
Example of how in humans social factors can increase the transmission of many communicable diseases?
The risk of HIV infection is high in places where there is limited access to:
Good healthcare- people are less likely to be diagnosed and treated for HIV, and the most effective anti-HIV drugs are less likely to be available, so the virus is more likely to be passed onto others.
Good health education- to inform people about how HIV is transmitted and how it can be avoided, e.g. through safe-sex practices like using condoms.
30
Primary, non-specific defences in animals: Skin?
This acts as a physical barrier, blocking pathogens from entering the body. It also acts as a chemical barrier by producing chemicals that are antimicrobial and can lower pH, inhibiting the growth of pathogens.
31
Primary, non-specific defences in animals: Mucous membranes?
These protect body openings that are exposed to the environment (such as mouth, nostrils, ears, genitals and anus). Some membranes secrete mucus- a sticky substance that traps pathogens and contains antimicrobial enzymes.
32
Primary, non-specific defences in animals: Blood clotting?
A blood clot is a mesh of protein (fibrin) fibres. Blood clots plug wounds to prevent pathogen entry and blood loss. They're formed by a series of chemical reactions that take place when platelets (fragments of old cells in the blood) are exposed to damaged blood vessels.
33
Primary, non-specific defences in animals: Inflammation?
The signs of inflammation include swelling, pain, heat and redness. It can be triggered by tissue damage- the damaged tissue releases molecules, which increase the permeability of the blood vessels, so they start to leak fluid into the surrounding area. This causes swelling and helps isolate any pathogens that may have entered the damaged tissue. The molecules also cause vasodilation (widening of the blood vessels), which increases blood flow to the affected area. This makes the area hot and brings white blood cells to the area to fight off any pathogens that may be present.
34
Primary, non-specific defences in animals: Wound repair?
The skin is able to repair itself in the event of an injury and re-form a barrier against pathogen entry. The surface is repaired by the outer layer of skin dividing and migrating to the edges of the wound. The tissue below the wound then contracts to bring the edges of the wound closer together. It is repaired using collagen fibres- too may collagen fibres and you'll end up with a scar.
35
Primary, non-specific defences in animals: Expulsive reflexes?
E.g. coughing and sneezing. A sneeze happens when the mucous membrane in the nostrils is irritated by things such as dust or dirt. A cough stems from the irritation in the respiratory tract. Both coughing and sneezing are an attempt to expel foreign objects, including pathogens, from the body. They happen automatically.
36
Physical plant defences: Waxy cuticles?
Most plant leaves and stems have a waxy cuticle, which provides a physical barrier against pathogen entry. It may also stop water collecting in the leaf, which could reduce the risk of infection by pathogens that are transfered between plants in water.
37
Physical plant defences: Plant cells are surrounded by cell walls?
These form a physical barrier against pathogens that make it past the waxy cuticle.
38
Physical plant defences: Plants produce a polysaccharide called callose?
Callose gets deposited between plant cell walls and plasma membranes during times of stress, e.g. pathogen invasion. Callose deposition may make it harder for pathogens to enter cells. Callose deposition at the plasmodesmata (small channels in the cell walls) may limit the spread of virus between cells.
39
Chemical plant defences: Antimicrobial chemicals?
Kill pathogens and inhibit their growth.
Examples:
- Some plants produce chemicals called saponins. These are thought to destroy the cell membranes of fungi and other pathogens.
- Plants also produce chemicals called phytoalexins, which inhibit the growth of fungi and other pathogens.
40
Chemical plant defences: Chemicals that are toxic to insects?
Some chemicals secreted by plants are toxic to insects- this reduces the amount of insect-feeding on plants and therefore reduces the risk of infection by plant viruses carried by insect vectors.
41
What are antigens?
Molecules (usally proteins or polysaccharides) found in the surface of cells.
42
What activates the immune response?
When the pathogen invaded the body, the antigens on its cell surface are identified as foreign, which activates cells in the immune system.
43
What is a phagocyte?
A type of white blood cell that carrier out phagocytosis
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Is phagocytosis specific or non-specific?
Non-specific
45
The process of phagocytosis?
1. Pathogen produces chemicals that attract phagocytes.
2. Phagocyte recognises foreign antigens on the pathogen.
3. The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome.
4. The phagosome combines with a lysosome (organelle that contains digestive enzymes) to form a phagolysosome. The enzymes break down the pathogen.
5. Phagocyte presents pathogen's antigens to activate other immune system cells. When a phagocyte does this is is known as an antigen-presenting cell (APC)
46
What do opsonins do?
Make it easier for phagocytes to engulf pathogens by attaching to foreign antigens to aid phagocytosis.
47
How do opsonins work?
Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively-charged phagocyte to get closer to the pathogen.
48
What is a neutrophil?
A type of phagocyte. They're the first white blood cells to respond to a pathogen inside the body.
49
What are T lymphocytes?
A type of white blood cell, their surface is covered with receptors.
50
What do T lymphocytes do?
Their receptors bind to antigens presented by APCs.
Each T lymphocyte has a different receptor on its surface.
When the receptor on the surface of a T lymphocyte meets a complementary antigen, it binds to it- so each t lymphocyte will bind to a different antigen.
51
What happens once the T lymphocyte has binded to the antigen?
The T lymphocyte is activated- this process is called clonal selection.
The T lymphocyte then undergoes clonal expansion- it divides to produce different clones of itself. Different types of T lymphocytes have different functions.
52
What do T helper cells do?
Release substances to activate B lymphocytes and T killer cells.
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What do T killer cells do?
Attach to and kill cells that are infected with a virus
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What do T regulatory cells do?
Supress the immune response from other white blood cells. This stops the immune system from mistakenly attacking the host's body cells .
55
What are B lymphocytes?
Another types of white blood cell
They're covered in proteins called antibodies
Antibodies bind to antigens to form an antigen-antibody complex.
56
What do B lymphocytes do?
Each B lymphocyte has a different shaped antibody on its surface.
When the antibody on the surface of the B lymphocyte meets a complementary shaped antigen its binds to it-so each B lymphocyte binds to a different antigen.
- This together with the substances released by T helper cells, activated B lymphocytes. This process is an example of clonal selection.
- The activated B lymphocyte divides by mitosis, into plasma cells and memory cells. This is an example of clonal expansion.
57
What is cell signalling and why is it important?
How cells communicate.
- A cell may release (or present) a substance that binds to the receptors on another cell- this is to casue a reponse of some kind in the other cell.
- It is really important in the immune reponse because it helps to activate all different types of white blood cells that are needed.
58
Example of cell signalling?
T helper cells release interleukins ( a type of cytokine) that bind to the receptors on B lymphocytes. This activated the B lymphocytes- T helper cells are signalling to the B lymphocytes that there’s a pathogen in the the body.
59
Example of cell signalling?
T helper cells release interleukins ( a type of cytokine) that bind to the receptors on B lymphocytes. This activates the B lymphocytes- the T helper cells are signalling to the B lymphocytes that there's a pathogen in the body.
60
What are plasma cells?
Clones of B lymphocytes.
They secrete loads of antibody, specific the antigen, into the blood.
These antibodies will bind to antigens on the surface of the pathogen to form lots of antigen-antibody complexes.
61
Antibody structure: Role of the constant region?
Allow binding to receptors on immune system cells, e.g. phagocytes.
The constant region is the same in all antibodies.
62
Antibody structure: Role of the disulfide bridges?
Hold the polypeptide chains of proteins together.
63
Antibody structure: Role of the hinge region?
Allows flexibility when the antibody binds to the antigen
64
Antibodies help clear infection by agglutinating pathogens?
Each antibody has two binding sites, so an antibody can bind to two pathogens at the same time- the pathogens become clumped together. Phagocytes then bind to the antibodies and the phagocytose a lot of pathogens all at once. Antibodies that behave in thsi way are known as agglutinins.
65
Antibodies help clear infection by neutralising toxins?
Like antigens, toxins have different shapes. Antibodies called anti-toxins can bind to toxins produced by pathogens. This prevents the toxins from affecting human cells, so the toxins are neutralised (inactivated). The toxin-antibody complexes are also phagocytosed.
66
Antibodies help clear infection by preventing the pathogen binding to human cells?
When antibodies bind to the antigens on pathogens, they lock the cell surface receptors that the pathogens need to bind to the host cells. This means the pathogen can't attach to or infect host cells.
67
Why is the primary response slow?
Because there aren't many B lymphocytes that can make the antibody needed to bind to it.
Eventually the body will produce enough of the right antibody to overcome the infection. Meanwhile the person will show symptoms of the disease.
68
Primary response: What happens after the person has been exposed to the antigen?
Both T and B lymphocytes produce memory cells. These memory cells remian high in the body for a long time.
Memory T lymphocytes remember the specific antigen and will recognise it second time round. Memory B lymphocytes record the specific antibodies need to bind to the antigen.
The person is now immune- their immune system has the ability to respond quickly to a second infection.
69
What happens in the secondary response?
- If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune reponse- the secondary reponse.
- Clonal selection happens faster. Memory B lymphocytes are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T lymphocytes are activated and divide into the correct type of T lymphocytes to kill the cell carrying antigen.
- The secondary reponse often gets rid of the pathogen before you begin to show symptoms.
70
How to identify a red blood cell in a blood smear?
Most of the cells are red blood cells, and they have no nucleus.
71
How to identify a neutrophil in a blood smear?
Its nucleus looks like 3 interconnected blobs- the posh way of saying it is that the nucleus is 'multi-lobed'. The cytoplasm of a neutrophil is grainy.
72
How to identify a lymphocyte in a blood smear?
- Much smaller than a neutrophil.
- The nucleus takes up most of the cell and there's very little cytoplasm to be seen (it's not grainy either)
73
How to identify a monocyte in a blood smear?
- It is the biggest white blood cell
- Has a kidney bean shaped nucleus
- A non-grainy cytoplasm
74
What is a monocyte?
The biggest white blood cell and a type of phagocyte.
75
What is active immunity?
This is the type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen.
76
What is natural active immunity?
This is when you become immune after catching a disease. E.g. if you have measles as a child, you shouldn't be able to catch it again in later life.
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What is artifical active immunity?
This is when you become immune after you've been given a vaccination containing a harmless dose of antigen.
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What is passive immunity?
This is the type of immunity you get from being given antibodies made by a different organism- your immune system doesn't produce any of its own.
79
What is natural passive immunity?
This is when a baby becomes immune due to the antibodies it recieves from its mother, through placenta and in breast milk.
80
What is artificial passive immunity?
This is when you become immune after being injected with antibodies from someone else. E.g. if you contract tetanus you can be injected with antibodies against the tetanus toxin , collected from blood donations.
81
What are autoimmune diseases caused by?
When an organisms immune system is't able to recognise self-antigens- antigens present on the organism's own cells. When this happens the immune system treats the self-antigens as foreign antigens and launches an immune reponse against the organism's own tissues.
82
Examples of autoimmune diseases?
Lupus- caused by the immune system attacking cells in the connective tissues. This damages the tissues and causes painful inflammation. Lupus can affect the skin and joints, as well as organs such as the heart and lungs.
Rheumatoid arthritis- caused by the immune system attacking cells in the joints. Again this causes pain and inflammation.
83
How do vaccinations work?
Contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you become immune without getting any of the symptoms.
84
What happens if most people in a community are vaccinated?
The disease becomes extremely rare. This means people who haven't been vaccinated are unlikely to get the disease, because there is no one to catch it from. This is called herd immunity. It helps to prevent epidermis- mass outbreaks of disease.
85
What type of antigens are in vaccinations?
Free or attached to a dead or attenuated (weakened pathogen).
86
What is the difference between vaccination and immunisation?
Vaccination is the administration of antigens (in a vaccine) into the body. Immunisation is the process by which you develop your immunity. Vaccination causes immunisation.
87
What routine vaccine is offered to everyone?
The MMR - protects agaisnt measles, mumps and rubella. The MMR is usually given to children as an injection at around 1 year old, and again before they start school. It contains a attenuated (weakened) measles, mumps and rubella viruses.
88
Why does the influenza vaccine change every year?
Because the antigens on the surface of influenza virus change regularly, forming new strains of the virus. Memory cells produced from vaccination with one strain of flu will not recognise others with different antigens. The strains are immunologically distinct.
89
Global issues of vaccinations?
Sometimes people are given a vaccine that protects them from a strain that prevents them causing an epidemic in another country- this helps to stop the strain from spreading globally.
90
What are antibiotics?
They are chemicals that kill or inhibit the growth of bacteria.
91
Why are antibiotics useful?
Becasue they can target bacterial cells without damaging human body cells.
92
History of antibiotics?
Penicillin was the first antibiotic to be isolated (By Fleming in 1928).
Antibiotic use became widespread from the mid-twentieth century- partly thanks to the sucessful treatment of soliders with penicillin in the 2nd World War.
93
How can antibiotic resistance occur?
1) There is genetic variation in a population of bacteria. Genetic mutations make some bacteria naturally resistance to antibiotic.
2) For bacterium, this ability to resist an antibiotic is a big advantage. It's better to be able to survive, even in a host who's being treated with antibiotics to get rid of the infection, and so it lives for longer and reproduces many more times.
3) This leads to the allele for antibiotic resistance being passed on to lots of offspring. It's an example of natural selection. This is how antibiotic resistance spreads and becomes more common in a population of bacteria over time.
94
What is the problem of antibiotic resistance?
This is a problem for people who became infected with these bacteria, because you can't easily get rid of the, with antibiotics.
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Examples of antibiotic-resistant bacteria: MRSA?
MRSA causes serious wound infections and is resistant to several antibiotics, including meticillin.
96
Examples of antibiotic-resistant bacteria: Clostridium difficile?
Infects the digestive system, usually causing problems in people who have already been treated with antibiotics. It is thought that the harmless bacteria that are normally present in the digestive system are killed by the antibiotics, which C. difficile is resistant to. This allows C. difficile to flourish. C. difficile produces a toxin, which causes severe diarrhoea, fever and cramps.
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How can antibiotic resistance be overcome?
Developing new antibiotics and modifying existing ones. This isn't easy though.
98
How can antibiotic resistance be prevented?
- Getting doctors to limit their use of antibiotics e.g. not prescribing them for minor infections or not prescribed to prevent infections.
- Patients that are prescribed them are advised to take all of the antibiotics they are prescribed to make sure the infection is fully cleared and all the bacteria have been killed.
99
Where are medications from?
Many medical drugs are are manufactured using natural compounds found in plants, animals or microorganisms.
100
How can possible sources of drugs be protected?
By maintaing the biodiversity on Earth. If we don't protect them, some species could die out before we get the chance to study them.
101
What is synthetic biology?
1) Involves using technology to design and make things like artifical proteins, cells and even microorganisms.
2) It has applications for lots of different areas, including medicine. For example, scientists are looking at enginnering bacteria to destroy cancer cells, while leaving the healthy body in tact.
102
What are personalised medications?
Medicines that are tailored to an individual's DNA. The theory is that if doctors have your genetic information, they can use it to predict how you will respond to different drugs and only prescribe the ones that will be most effective for you.
