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Biology > 11. Communicable Diseases > Flashcards

11. Communicable Diseases Flashcards

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1
Q

What are the pathogens that cause disease?

A

Bacteria, Fungi, Viruses, Protoctista

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2
Q

What is a pathogen?

A

Organisms that cause disease.

The organism in which they live is the host

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3
Q

What is Bacteria?

A

They belong to the kingdom Prokaryotae.
Their cells are smaller than eukaryotic cells, but can reproduce rapidly.
They damage cells or release waste products or toxins that are toxic to the host.

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4
Q

What are Fungi?

A

Live in the skin of an animal.
The hyphae form a mycelium that grows under skin surface.
The hyphae release extracellular enzymes to digest the surrounding tissue which causes decay.

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5
Q

What are Viruses?

A

They invade cells and take over the genetic machinery.
They then cause the cell to manufacture more copies of the virus.
The host cell eventually bursts, releasing many new viruses.

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6
Q

What are Protoctista?

A

Animal-like organisms that enter host cells and feed on the contents as they grow.
e.g. The malarial parasite Plasmodium feed on the haemoglobin inside red blood cells.

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7
Q

What diseases are caused by bacteria?

A

Tuberculosis, Bacterial meningitis, ring rot (in plants)

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8
Q

What diseases are caused by viruses?

A

HIV/ AIDS, Influeza, Tobacco mosaic virus (in plants)

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9
Q

What diseases are caused by fungi?

A

Black sigatoka (in plants), ringworm (cattle), Athlete’s foot (humans)

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10
Q

What diseases are caused by protoctista?

A

Blight (tomatoes and potatoes), Malaria (humans)

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11
Q

What are is the life cycle of a pathogen?

A

Travel from one host to another (transmission)
Entering the host’s tissues
Reproducing
Leaving the host’s tissues

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12
Q

What is transmission?

A

How pathogenic organisms are transmitted between organisms.

Can be direct or indirect

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13
Q

What are the different forms of direct transmission?

A

Direct physical contact between people and plants.

Via bodily fluids

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14
Q

What factors affect transmission?

A

Overcrowding
Poor ventilation
Poor health- particularly if a person has HIV/ AIDS, as they are more likely to contract other disease.
Poor diet

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15
Q

What is indirect transmission?

A

A vector.
Air and waterborne transmission (sneezes and spores).
Contact with an infected surface (fomites).

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16
Q

How are pathogens directly transmitted in plants?

A

Pathogens are present in soil and will infect the plant by entering the roots.
Pathogens in the leaves are distributed when the leaves shed and carry the pathogen back to the soil.

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17
Q

How are pathogens indirectly transmitted in plants?

A

Transmission of plant pathogens from an insect attack.
Spores or bacteria attached to a burrowing insect.
The insect acts as a vector.

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18
Q

How does climate affect the spread of disease?

A

Many protoctists, bacteria and fungi can grow and reproduce more rapidly in warm and moist conditions.
In cooler climates, these pathogens may be damaged or even killed.
There is a greater variety of diseases to be found in warmer climates.

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19
Q

What are passive defences?

A

These are defences present before infection, and their role is to prevent entry and spread of the pathogen.
Passive defences include physical barriers and chemicals.

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20
Q

What are the physical defences in plants?

A

Cellulose cell wall, Lignin thickening, Waxy cuticles, Bark, Stomatal closure, Callose and Tylose formation

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21
Q

What is the role of Cellulose cell wall?

A

This acts as a physical barrier and most plant cell walls contain a variety of chemical defences that can be activated when a pathogen is detected.

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22
Q

What is the role of Lignin thickening?

A

Lignin is deposited in cell walls.

Lignin is waterproof and almost completely indigestible.

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23
Q

What is the role of Waxy cuticles?

A

These prevent water collecting on the cell surfaces. Since pathogens collect in water and need it to survive, it is a passive defence.

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24
Q

What is the role of Bark?

A

Most bark contains a variety of chemical defences that work against pathogenic organisms.

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25
Q

What is the role of Stomatal closure?

A

Stomata are possible points of entry for pathogens in plants.
Stomata closure is controlled by the guard cells.
When pathogenic organisms are detected, the guard cells will close the stomata.

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26
Q

What is the role of Callose?

A

It is a large polysaccharide that is deposited between cell walls and cell membranes in the cells next to the infected cells.
Prevents pathogens entering the plant cells around the site of infection

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27
Q

What is the role of Tylose formation?

A

It is a balloon-like swelling that fills the xylem vessel.
It contains a high concentration of chemicals that are toxic to pathogens.
It plugs the vessel so it can no longer carry water and prevents spread of pathogens.

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28
Q

What are the active defences in plants?

A

Cell walls become thickened and strengthened with cellulose.
Deposition of callose strengthens the cell wall and blocks plasmodesmata.
Oxidative bursts produce highly reactive oxygen molecules, damaging cells of invading organisms.

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29
Q

How are defences in plants stimulated?

A

Specific chemicals in a pathogen’s cell walls can be detected by plant cells. They respond by stimulating their chemical, physical and active defences

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30
Q

What is Necrosis?

A

Deliberate cell suicide.
A few cells are sacrificed to save the rest of the plant.
This can limit the pathogen’s access to water and nutrients and therefore stop it spreading further around the plant.

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31
Q

What are the primary defences in humans?

A

The skin, blood clotting, skin repair, mucous membranes, coughing and sneezing, inflammation

32
Q

What is the epidermis?

A

The outer layer of skin.

33
Q

How does the skin act as a primary defence?

A

The epidermis consists of keratinocyte cells which contain the protein keratin and act as an effective barrier to pathogens.

34
Q

How does blood clotting and skin repair occur?

A

An enzyme cascade is activated by clotting factors such as platelets.
Once a clot has formed it dries out and forms a scab which draws the sides of a cut together as it shrinks.
The skin is repaired beneath this by deposition.
New blood vessels grow eventually to supply oxygen and nutrients to the new tissues.

35
Q

What is the role of mucous membranes?

A

The epithelial layer contains mucous-secreting (goblet) cells that trap any pathogens.
Cilliated cells waft them to the oesophagus to be swallowed.
The pathogen’s enzyme is denatured by the low pH of the stomach acid.

36
Q

Where else are mucous membranes found?

A

the gut, anus, ears and nose

37
Q

What is the role of inflammation?

A

In response to injury and infection, specialised immune cells called mast cells release histamine.
This causes blood vessels to widen (vasodilation).
This increases blood flow to the area.
Phagocytes and clotting elements can then accumulate at the site of injury or infection.

38
Q

What are secondary defences?

A

They are used to combat pathogens that have entered the body.

39
Q

What are antigens?

A

Chemical markers on a pathogen’s outer membrane that the body recognises as foreign.

40
Q

What are phagocytes?

A

Specialised cells in the blood and tissue fluid that engulf and digest the pathogens.

41
Q

What are neutrophils?

A

The most common phagocytes.
They are manufactured in the bone marrow.
They contain a large number of lysosomes.
They engulf and digest pathogens and die shortly after.

42
Q

What are macrophages?

A

Manufactured in the bone marrow.
Engulfs pathogens and ‘saves’ the antigen and becomes an antigen-presenting cell.
Other cells of the immune system can then recognise the antigen.

43
Q

What is antigen presentation?

A

Antigen-presenting cells move around the body and come into contact with T and B lymphocytes to activate a full immune response.
It is the role of the antigen-presenting cells is to increase the chances that the correct antigens come into contact with T and B lymphocytes.

44
Q

What are T and B lymphocytes?

A

White blood cells with a large nucleus and specialised receptors on their plasma membrane.

45
Q

What is the immune response?

A

It produces antibodies which neutralise foreign antigens.
It also provides long-term protection from the disease by producing immunological memory through the release of memory cells.

46
Q

What cells are produced in the immune response?

A 
T helper cells
T killer cells
T memory cells
T regulator cells
B lymphocytes that develop into...
Plasma cells
B memory cells
47
Q

What are T helper cells?

A

Cells that release signalling molecules to stimulate the immune response.
They stimulate B-cells to make antibodies and killer T cells to develop.

48
Q

What are T killer cells?

A

Cells that attack and kill our own body cells that are infected by a pathogen.
They do this by secreting substances that kill the infected cells.

49
Q

What are T memory cells?

A

Cells that remain in the blood for a long time, providing long-term immunity.

50
Q

What are T regulator cells?

A

Cells that are involved with the inhibiting or ending the immune response

51
Q

What are plasma cells?

A

They circulate in the blood, manufacturing and releasing the antibodies.

52
Q

What is cell signalling?

A

How cells communicate through the release of cytokines.

53
Q

What are B lymphocytes?

A

B-cells develop from stem cells in the bone marrow.

They can differentiate into plasma cells and b lymphocytes.

54
Q

What are the main 3 stages of the immune response?

A 
Clonal selection
Clonal expansion (proliferation)
Differentiation
55
Q

What is Clonal selection?

A

When a B or T cell that recognises an antigen is selected from the pre-existing cell pool.

56
Q

What is Clonal expansion (proliferation)?

A

When the activated lymphocyte increases in numbers to be effective.
They do this through mitotic cell division.

57
Q

What is differentiation?

A

When clones of the selected T and B lymphocytes develop into a range of useful cells in the immune response.

58
Q

How is the structure of an antibody adapted to its function?

A

The constant region is exposed and allows phagocytosis to occur.
The antigen binding sites are specific to the antigens on the surface of the pathogens.
The disulfide bridge allows the antibodies to bind to two antigens.

59
Q

What are the three types of antibodies?

A

Osponins
Agglutinins
Anti-toxins

60
Q

What are opsonins?

A

They neutralise pathogens by binding to antigens.
This means antigens cannot bind to cells to enter them.
They also act as binding sites for phagocytic cells so they can easily bind and destroy the pathogen.

61
Q

What are agglutinins?

A

When an antibody ‘crosslinks’ pathogens by binding an antigen on one pathogen with one binding site and then an antigen on another pathogen with its other binding site.
Forces pathogens to clump together and stay on one place.

62
Q

What are the advantages of agglutinins?

A

The agglutinated pathogens are physically impeded.

They are readily engulfed by phagocytes.

63
Q

What are anti-toxins?

A

Antibodies bind to molecules that are released by pathogenic cells.
These can be toxic and the actions of anti-toxins renders them harmless.

64
Q

What is the secondary immune response?

A

There will be B and T memory cells circulating in the blood.
These can recognise the specific antigens and act quickly.
The concentration of antibodies rises sooner and reaches a higher concentration.
It is usually quick enough to prevent any symptoms being detected.

65
Q

What is vaccination?

A

Provides immunity by deliberate exposure to antigenic material.
The immune system treats the antigenic material as a real disease.
The immune system manufactures memory cells that provide long-term immunity.
Can be injected or taken orally.

66
Q

What different forms does the antigenic material in vaccines come in?

A

Whole, living microorganisms,
A harmless or attenuated version of the pathogenic organism,
A dead pathogen,
A preparation of antigens from the pathogen,
A toxoid (harmless version of a toxin)

67
Q

What is herd vaccination?

A

Using a vaccine to provide immunity to all or almost all of the population at risk.
Once enough people are immune, the disease can no longer be spread through the population.
‘herd immunity’ is achieved

68
Q

What is ring vaccination?

A

All the people in the vicinity of new cases are vaccinated.

Also used in livestock diseases.

69
Q

What can be done once an epidemic has been eradicated?

A

The routine vaccination programme can be relaxed.
However, some pathogens can undergo genetic mutations which change their antigens and make them unrecognisable to memory cells.
This will cause the incidence of the disease to increase.
New strains of pathogens must be monitored.

70
Q

What are the different types of immunity?

A

It can be achieved naturally or artificially and it can be active or passive

71
Q

What is Natural Immunity?

A

Achieved through normal life processes
Can be active or passive.
Active= Immunity is provided by antibodies made in the immune system as a result of infection.
Passive= Antibodies provided via the placenta or via breast milk. This is short-lived as memory cells are not produced.

72
Q

What is Artificial Immunity?

A

Achieved through medical intervention.
Can be active or passive
Active= Immunity provided by antibodies made in the immune system as a result of vaccination.
Passive= Immunity provided by injection of antibodies made by another individual (plasma treatment).

73
Q

What is Active immunity?

A

Achieved when the immune system is activated and manufactures its own antibodies.

74
Q

What is Passive Immunity?

A

Is achieved when the antibodies are supplied from another source.

75
Q

What different ways of discovering new medicines are there?

A 
Accidental discovery
Traditional remedies
Observation of wildlife
Research into disease-causing mechanisms
Personalised medicine
76
Q

What is an autoimmune disease?

A

When the immune system attacks a part of the body.
Antibodies start to attack their own antigens.
e.g. arthritis and lupus

Biology (13 decks)

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