12 Communicable diseases Flashcards
1
Q
What are communicable diseases?
A
Diseases that can be passed from one organism to another, of the same or different species.
2
Q
What are pathogens?
A
- Microorganisms that cause disease.
- Types of pathogens include: bacteria, virsues, fungi and protoctista.
3
Q
What are vectors?
A
A living or non living factor that transmits a pathogen from one organism to another e.g malaria mosquito
4
Q
Which two ways can bacteria be classified into?
A
- By their basic shapes: rod shaped, spherical, corkscrew
- By their cell walls: the two main types of bacterial cell walls have different structures and react differently with a process called Gram staining.
5
Q
What colour do Gram positive bacteria look under the light?microscope?
A
Purple-blue
6
Q
What colour do gram negative bacteria look under the light microscope?
A
Red
7
Q
What are viruses?
A
Viruses are non-living infectious agents.
8
Q
What size is a virus?
A
At 0.02-0.3um in diameter, they are around 50 times smaller in length than the average bacterium.
9
Q
What is the basic structure of a virus?
A
Genetic material (DNA or RNA) surrounded by protein.
10
Q
How do viruses function?
A
- Viruses invade living cells, where the genetic material of the virus takes over the biochemistry of the host cells to make more viruses.
- Viruses reproduce rapidly and evolve by developing adaptations to their host, which makes them very successful pathogens.
11
Q
What are bacteriophages?
A
Viruses that attack bacteria by taking over the bacterial cells and using them to replicate and destroy the bacteria at the same time.
12
Q
Are all naturally occuring viruses pathogenic?
A
Yes
13
Q
What are protocista?
A
- A group of eukaryotic organisms with a wide variety of feeding methods.
- A small percentage of protoctista act as pathogens.
- The protists which cause disease are parasitic- they use people or animals as their host organism.
14
Q
What are fungi?
A
- Fungi are eukaryotic organisms that are often multicellular.
- Fungi cannot photosynthesise and they digest their food extracellularly before absorbing the nutrients,
- Many fungi are saprophytes which means they feed on dead and decaying matter.
- However, some fungi are parasitic, feeding on living plants and animals.
15
Q
Which different ways do pathogens attack?
A
1) Viruses take over the cell metabolism.
- The viral genetic material gets into the host cell and is inserted into the host DNA.
- The virus then uses the host cell to make new viruses which then burst out of the cell, destroying it and then spread to infect other cells.
2) Some protoctista also take over cells and break them open as the new generation emerge, but they do not take over the genetic material of the cell.
- They simply digest and use the cell contents as they reproduce. E.g malaria
3) Fungi digest living cells and destroy them.
- This combined with the response of the body to the damage caused by the fungus gives the symptoms of disease.
16
Q
Which toxins damage host tissues?
A
- Most bacteria and some fungi produce toxins which affect the host cells and cause disease
- bacterial toxins damage the host cells by breaking down the cell membranes.
17
Q
What is the tobacco mosaic virus?
A
- A virus that infects tobacco plants and around 150 other species including tomatoes, peppers.
- It damages leaves,flowers and fruit, stunting growth and reducing yields.
18
Q
What is potato blight?
A
- It is caused by the protoctist oomycete.
- The hyphae penetrate host cells, destroying leaves, tubes and fruit.
19
Q
What is black sigatoka?
A
- A banana disease caused by a fungus which attacks and destroys the leaves.
- The hyphae penetrate and digest the cells, turning the leaves black.
20
Q
What is tuberculosis?
A
- A bacterial disease of humans, cows, pigs etc.
- Commonly caused by Mycobacterium tuberculosis.
- TB damages and destroys lung tissue and suppresses the immune system, so the body is less able to fight off other diseases.
21
Q
What is bacterial meningtis?
A
- A bacterial infection of the meninges of the brain which can spread into the rest of the body causing septicaemia (blood poisoning) and rapid death.
22
Q
What causes AIDS? (acquired immunodeficiency syndrome)?
A
HIV causes AIDS.
Human immunodeficiency virus
23
Q
What does HIV do?
A
- HIV is a retrovirus with RNA as its genetic material, has reverse transcriptase enzyme that transcribes RNA into a single DNA strand in host cells, this DNA interacts with genetic material of host cell
- Targets T-helper cells in immune system, gradually destroying immune system so that people are more susceptible to other infections like TB and pneumonia
24
Q
How is HIV passed from one person to another?
A
Via bodily fluids, most commonly through unprotected sex, shared needles, contaminated blood products and from mothers to their babies during pregnancy, birth or breast feeding.
25
What is influenza?
- A viral infection of the cilated epithelial cells in the gas exchange system.
- It kills them, leaving the airways open to secondary infection.
26
What is malaria?
- It is caused by the protoctista Plasmodium and spread by the bites of infected Anopheles mosquitoes.
- The plasmodium parasite invades the red blood cells, liver and even the brain.
27
What is ringworm?
- A fungal disease affecting mammals including cattle, dogs, cats and humans.
- It causes grey-white, crusty, infectious, circular areas of skin.
- In cattle, ringworm is usually caused by Trichophyton verrucosum.
28
What is athlete's foot?
- A human fungal disease caused by Tinia pedia, a form of human ring work that grows on and digests the warm, moist skin between the toes.
- It causes cracking and scaling.
29
What the two main types of transmission?
1) Direct transmission
| 2) Indirect transmission
30
How are pathogens directly transmitted?
1) Direct contact
- Kissing or any contact with the body fluids of another person
- Direct skin-to-skin contact
- Microorganisms from faeces transmitted on hands
2) Inoculation
- Through a break in skin e.g during sex (HIV/AIDS)
- Through an animal bite
- Through a puncture wound or sharing needles
3) Ingestion: Taking in contaminated food or drink
31
How are pathogens indirectly transmitted?
1) Fomites : Inanimate objects such as bedding, socks can transfer pathogens.
2) Droplet infection: Inhaling droplets of saliva and mucus which contain pathogens.
3) Vectors: A vector transmits communicable pathogens from one host to another. E.g mosquitos, rats, bats
32
What factors increase the probability of catching a communicable disease?
- Overcrowded living and working conditions
- Poor nutrition
- Poor disposal of waste
- Climate change (can introduce new vectors and new diseases)
33
How are pathogens directly transmitted in plants?
Via direct contact of a healthy plant with any part of a diseased plant.
34
How are pathogens indirectly transmitted in plants?
1) Soil contamination: Infected plants often leaves pathogens or reproductive spores from protoctista or fungi in the soil. These can infect the next crop.
35
What polysaccharide do plants produce when attacked by pathogens?
Callose
36
What happens when a plant is attacked by pathogen?
1) Within minutes of inital attack, callose is synthesised and deposited between the cell walls and the cell membranes. This acts as barriers, preventing the pathogens entering the plant cells around the site of infection.
2) Large amounts of callose continue to be deposited in cell walls. Lignin is added, making the mechanical barrier to invasion even thicker and stronger.
3) Callose blocks sieve plates in the phloem, sealing off the infected part and preventing the spread of pathogens.
4) Callose is deposited in the plasmodesmata between infected cells and their neighbours, sealing them off from the healthy cells and helping to prevent the pathogen spreading.
37
What are the chemical defences against pathogens?(Plants)
- Insect repellents
- Insecticides
- Antibacterial compounds including antibiotics
- Antifungal compounds: e.g chitinases- enzymes that break down the chitin in fungal cell walls.
- Anti-oomycetes: E.g glucanases- enzymes made by some plants that break down glucans.
- General toxins- cyanide
38
What barriers does the body have to prevent the entry of pathogens?
1) The skin covers the body and prevents the entry of pathogens.
- It has a skin flora of healthy microorganisms that outcompete pathogens for space on the body surface.
- It also produces sebum, an oily substance that inhibits the growth of pathogens.
2) The airways of the gas exchange system are lined by mucous membranes that secrete sticky mucus.
- This traps microorganisms and contains lysozymes, which destroy bacterial and fungal cell walls.
- Mucus also contain phagocytes, which remove remaining pathogens.
3) Lysozymes in tears and urine, and the acid in our stomach, also help to prevent pathogens getting into our body.
39
What substances are secreted by platelets when you cut yourself?
- Thromboplastin, an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot.
- Serotonin, which makes the smooth muscle in the walls of the blood vessels contract, so they narrow and reduce the supply of blood to the area.
40
What happens after blood clots?
- The clot dries out, forming a hard, tough scab that keeps pathogens out. This is the first stage of wound repair.
- Epidermal cells below the scab start to grow, sealing the wound permanently, while damaged blood vessels regrow.
- Collagen fibres are deposited to give the new tissue strength.
- Once the new epidermis reaches normal thickness, the scab sloughs off and the wound is healed.
41
What is the inflammatory response?
- It is a localised response to pathogens resulting in inflammation at the site of a wound.
- It is characterised by pain, heat, redness and swelling of tissue.
42
What chemicals do mast cells release?
Histamines and cytokines.
43
What do histamines do?
1) Histamines make the blood vessels dilate, causing localised heat and redness.
- The raised temperature helps prevent pathogens reproducing.
2) Histamines make blood vessel walls more leaky, so blood plasma is forced out. Tissue fluid causes swelling and pain.
44
What do cytokines do?
- Cytokines attract white blood cells to the site.
| - They dispose of pathogens by phagocytosis.
45
What are antigens?
Identifying chemical on the surface of a cell that triggers an immune response (involves the production of antibodies)
46
What is the specific immune system?
- Also known as active or acquired immunity.
- It is slower than the non-specific responses- can take up to 14 days to respond effectively to a pathogen invasion.
- However, the immune memory cells mean it reacts very quickly to a second invasion by the same pathogen.
47
What are antibodies?
- Antibodies are Y-shaped glycoproteins called immunoglobulins, which bind to a specific antigen on the pathogen or toxin that has triggered the immune response.
48
What are antibodies made up of?
- Two identical long polypeptide chains called heavy chains and two much shorter identical chains called light chains.
- They are held together by disulfide bridges.
49
What forms when an antibody bind to an antigen?
Antigen-antibody complex.
| The binding site is an area of 110 amino acids on both heavy & light chains known as variable region.
50
Why is it called the constant region?
Because the rest of the antibody molecule is always the same.
51
How do antibodies defend the body?
1) Prevents the pathogen binding to human cells.
- When antibodies bind to antigens on pathogens they block the cell-surface receptors that pathogens need to bind onto host cells.
- This means the pathogen can’t attach to or to infect the host cells.
2) Antibodies act as agglutins (chemicals causing pathogens to clump together causing pathogens carrying antigen-antibody complexes to clump together. This helps prevent them spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time.
3) Antibodies can act as anti-toxins, binding to the toxins produced by pathogens and making them harmless.
52
What are lymphocytes?
White blood cells that make up the specific immune system.
53
What are the two types of lymphocytes?
1) B lymphocytes which mature in the Bone marrow.
| 2) T lymphocytes which mature in the Thymus gland.
54
What are the main types of T lymphocytes?
1) T helper cells
2) T killer cells
3) T memory cells
4) T regulator cells
55
What are the main types of B lymphocytes?
1) Plasma cells
2) B effector cells
3) B memory cells
56
What are T helper cells?
- These have CD4 receptors on their cell-surface membrane, which binds to the surface antigens.
- They produce interleukins, which are a type of cytokine. (cell-signalling molecule).
- The interleukins made by the T helper cells stimulate the activity of B cells, which increases antibody production, stimulates production of other types of T cells and attracts and stimulates macrophages to ingest pathogens with antigen-antibody complex.
57
What are T killer cells?
- These destroy the pathogen carrying the antigen.
- They produce a chemical called perforin, which kills the pathogen by making holes in the cell membrane so it is freely permeable.
58
What are T memory cells?
- These live for a long time and are part of the immunological memory.
- If they meet an antigen a second time, they divide rapidly to form a huge number of clones of T killer cells that destroy the pathogen.
59
What do T regulator cells do?
- These cells suppress the immune system, acting to control and regulate it.
- They stop the immune response once a pathogen has been eliminated, and make sure the body recognises self antigens and does not set up autoimmune response.
60
What do plasma cells do?
- They produce antibodies to a particular antigen and release them into the circulation.
- An active plasma cell only lives for a few days but produces around 2000 antibodies per second while it is alive and active.
61
What are B effector cells?
These divide to form the plasma cell clones.
62
What are B memory cells?
- These live for a long time and are part of the immunological memory.
- They are programmed to remember a specific antigen and enable the body to make a very rapid response when a pathogen carrying that antigen is encountered again.
63
Why do we get fevers?
- When a pathogen invades your body, cytokines stimulate your hypothalamus to reset the thermostat and your temperature goes up.
- Most pathogens reproduce best at or below 37 degrees. Higher temperatures inhibit pathogen reproduction.
- The specific immune system works faster at higher temperatures.
64
What are phagocytes?
Phagocytes are specialised white cells that engulf and destroy pathogens.
65
What are the two types of phagocytes?
Neutrophils and macrophages
66
What do phagocytes do?
- Phagocytes build up at the site of an infection and attack pathogens.
- Sometimes you can see pus in a spot, cut or wound.
- Pus consists of dead neutrophils and pathogens.
67
What are the stages of phagocytosis?
1) Pathogens produce chemicals that attract phagocytes.
2) Phagocytes recognise non-human proteins on the pathogen. This is a response not to a specific type of pathogen, but simply a cell or organism that is non-self.
3) The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome.
4) The phagosome combines with a lysosome to form a phagolysosome.
5) Enzymes from the lysosome digest and destroy the pathogen.
68
What is the major histocompability complex (MHC)?
- Special glycoproteins in the cytoplasm.
| - It moves pathogen antigens to the macrophage's own surface membrane, becoming an antigen-presenting cell.
69
What chemical do phagocytes that engulf a pathogen produce?
Cytokines
70
What do cytokines do?
- Cytokines act as cell-signalling molecules, informing other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation.
- Cytokines can also increase body temperature and stimulate the specific immune system.
71
What are opsonins?
- Opsonins are chemicals that bind to pathogens and 'tag' them so they can be more easily recognised by phagocytes.
- Phagocytes have receptors on their cell membranes that bind to common opsonins, and the phagocyte then engulfs the pathogen.
- E.g immunoglobulin.
72
What is the cell mediated response?
1) In the non-specific immune system macrophages engulf and digest pathogens in phagocytosis. They process the antigens from the surface of the pathogen to form antigen-presenting cells.
2) Receptors on some of the T helper cells fit the antigens. The T helper cells become activated and produce interleukins, which stimulate more T cells to divide rapidly by mitosis. They form clones of identical activated T helper cells that all carry the right antigen to bind to a particular pathogen.
3) These cloned T cells can then differentiate into different specialised T cells:
- Memory T cells to enable a rapid response to reinfection of the same pathogen.
- Cytotoxic T cells kill abnormal cells and infected body cells. They release a protein called perforin which create pores (holes) in the cell membrane. This allows all substances to move into the cell and causes cell death.
- Helper T cells stimulate B cells to divide and secrete antibodies.
- T cells also stimulate phagocytosis of pathogens.
73
What is the humoral response?
- This is the response to antigens found outside the cells, e.g bacteria and fungi. - - Helper T cells stimulate the B cells and initiate the humoral response, which involves antibodies.
1) Activated T helper cells bind to the B cell APC. This is clonal selection- the point at which the B cell with the correct antibody to overcome a particular antigen is selected for cloning.
2) Interleukins produced by the activated T helper cells activate the B cells.
3) The activated B cell divides by mitosis to give clones to plasma cells and B memory cells (clonal expansion).
4) Cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to the antigens and disable them, or act as opsonins or agglutinins.
- This is the primary immune response and it can take days or even weeks to become fully effective against a particular pathogen.
5) Some cloned B cells develop into B memory cells. If the body is infected by the same pathogen, the B memory cells divide rapidly to form plasma cell clones. These produce the right antibody and wipe out the pathogen very quickly, before it can cause the symptoms of disease. This is the secondary immune response.
74
What is an autoimmune disease?
A disease where the immune system stops recognising 'self' cells and starts to attack healthy body tissue.
75
What are some common autoimmune disease?
Type 1 diabetes, rheumatoid arthritis, lupus
76
Which body part is affected by type 1 diabetes?
The insulin-secreting cells of the pancreas.
77
What treatment is there for type 1 diabetes?
- Insulin injections
- Pancreas transplant
- Immunosuppressant drugs
78
What body part is affected by rheumatoid arthritis?
- Joints: especially in the hands, wrists, ankles and feet.
79
What treatment is there for rheumatoid arthritis?
- No cure
- Anti-inflammatory drugs
- Steroids
- Immunosuppressants
- Pain relief
80
Which body part is affected by lupus?
- Skin and joints
| - Can attack any organ in the body including kidneys, liver, lungs or brain.
81
What treatment is there for lupus?
- No cure
- Anti-inflammatory drugs
- Steroids
- Immunosuppressants
- Various others
82
What is artificial passive immunity?
- For certain potentially fatal diseases, antibodies are formed in one individual, extracted and then injected into the bloodstream of another individual.
- This artificial passive immunity gives temporary immunity- it doesn't last long but it can be livesaving.
- E.g tetanus antibodies extracted from the blood of horses, preventing the development of the disease but not providing long-term immunity.
83
What is artificial active immunity?
- In artificial active immunity, the immune system of the body is stimulated to make its own antibodies to a safe form of an antigen (a vaccine), which is injected into the blood stream.
84
How are vaccines produced?
1) The pathogen is made safe in one of a number of ways so that the antigens are intact but there is no risk of infection.
- Vaccines may contain:
- Killed or inactivated bacteria and viruses, for example, whooping cough
2) Small amounts of the safe antigen, known as the vaccine, are injected into the blood.
3) The primary immune response is triggered by the foreign antigens and your body produces antibodies and memory cells as if you were infected with a live person.
4) If you come into contact with a live pathogen, the secondary immune response is triggered and you destroy the pathogen before you suffer symptoms of the disease.
85
What is natural active immunity?
- When you meet a pathogen for the first time, your immune system is activated and antibodies are formed, which results in the destruction of the antigen.
- The immune system produces T and B memory cells so if you meet a pathogen for a second time, your immune system recognises the antigens and can immediately destroy the pathogen, before it causes disease symptoms.
- It is known as active because the body has itself acted to produce antibodies and/or memory cells.
86
What is natural passive immunity?
- Antibodies cross the placenta from the mother to her fetus while the baby is in the uterus, so it has some immunity to disease at birth.
- The first milk a mammilian mother makes is called colostrum, which is very high in antibodies.
- The infant gut allows these glycoproteins to pass into the bloodstream without being digested.
- So within a few days of birth, a breast-fed baby will have the same level of antibody protection against disease as their mother.
87
What is an epidemic?
An epidemic is when a communicable disease spreads rapidly to a lot of people at a local or national level.
88
What is a pandemic?
A pandemic is when the same disease spreads rapidly across a number of countries and continents.
89
What is herd immunity?
When a significant number of people in the population have been vaccinated, this gives protection to those who do not have immunity.
90
What is pencillin?
The first widely used, safe antibiotic, derived from a mould, Pencillium notatum.
91
Drugs and their uses:
- Docetaxel/paclitaxel: treatment of breast cancer
- Aspirin: painkiller, anti-coagulant, anti-inflammatory
- Prialt: New pain-killing drug 1000 times more effective than morphine
- Vancomycin: One of the most powerful antibiotics
- Digoxin: powerful heart drug used to treat atrial fibrillation and heart failure.
92
What is pharmocogenetics?
The science of interweaving knowledge of drug actions with personal genetic material.
93
What is personalised medicine?
A combination of drugs that work with your individual combination of genetics and disease.
94
How is synthetic biology used?
- Using techniques of genetic engineering, we can develop populations of bacteria to produce much needed drugs that would otherwise be too rare, too expensive or just not available.
- It enables the use of bacteria as biological factories.
95
What is selective toxicity?
The ability to interfere with the metabolism of a pathogen without affecting the cells of the host.
96
what are cytokines ?
cell signalling molecules
97
what are interleukins ?
type of cytokines released by white blood cells
98
difference between specific and non-specific immune response ?
Non-specific is the general response when body detects pathogens, response is carried out by phagocytes. Specific immune response is carried out by lymphocytes and process a specific response to certain types of antigen, produces specific antibodies to those antigens.
