Chapter 12 Communicable Diseases Flashcards
1
Q
What are the different types of pathogens?
A
Bacteria
Viruses
Fungi
Protoctista
2
Q
What are the different modes of action used by pathogens to cause disease?
A
Pathogens can damage the host tissues directly or produce toxins which damages the host tissues.
3
Q
How do viruses cause disease?
A
The viral genetic material is inserted into the host cells DNA. The virus then uses this host cell to make new viruses which burst out of the cell, destroying it and spreading the infection to other cells.
4
Q
How does protoctista cause disease?
A
Protoctista take over the cells, breaking them open as the new generation emerge, however they do not take over the genetic material of the cell.
Instead the Protoctista digest and use the cell contents as they reproduce.
5
Q
How does fungi cause disease?
A
Fungi digests living cells and destroys them.
However, some Fungi may also produce toxins that also affect the host cells.
6
Q
How does bacteria cause disease?
A
Produce toxins that can damage host cells either by breaking down the cell membrane, inactivating enzymes or interfering with the host cells genetic material so the cell cannot divide.
7
Q
What type of pathogen causes Tuberculosis?
A
Bacteria (affects humans and animals)
8
Q
What type of pathogen causes Ring rot?
A
Bacteria (affects potato and tomato)
9
Q
What type of pathogen causes HIV/AIDS?
What is the effect of the pathogen?
A
Virus
The virus destroys the immune system so individuals become vulnerable to secondary infections
10
Q
What type of pathogen causes Influenza?
A
Virus
11
Q
What type of pathogen causes Tobacco Mosaic virus?
What is the effect of the pathogen?
A
Virus
The Tobacco plant leaves become damaged resulting in stunted growth
12
Q
What type of pathogen causes Malaria?
A
Protoctista (carried by mosquitoes which act as vectors)
13
Q
What type of pathogen causes Potato/ Tomato blight?
A
Protoctista
14
Q
What type of pathogen causes Black Sigatoka?
What is the effect of the pathogen?
A
Fungi (affects Banana)
The fungi destroys the leaves
15
Q
What type of pathogen causes Athletes foot?
A
Fungi
16
Q
What is a vector?
A
Carries a pathogen spreading the disease from one organism to another
17
Q
What type of pathogen causes Bacterial Meningitis?
What is the effect of this pathogen?
A
Bacteria
Affects the brain but can spread to the rest of the body causing blood poisoning and if left untreated death.
18
Q
What is the effect of Influenza?
A
A viral infection which affects the Ciliated epithelial cells in the gaseous exchange system. It kills them and leaves the airways open to secondary infection.
It can rapidly mutate ——> new strains causing epidemics as there are no antibodies available.
New vaccination are constantly needed to be made.
19
Q
What measures could be put in place to prevent the spread of Malaria?
A
Caused by a Protoctista which is spread via the mosquito which acts as the vector.
Preventative measures can be put in place to control the vector, using mosquito nets, insecticides and removing stagnant water to reduce breeding.
20
Q
What is direct transmission?
A
The pathogen is transferred directly from one individual to another
21
Q
How can pathogens be directly transmitted between animals?
A
Direct contact
Inoculation
Ingestion
22
Q
Give some examples of direct contact
A
Kissing
Direct skin-to-skin contact
Sexual transmission
Contact with bodily fluids
23
Q
Give some examples of Inoculation
A
Through broken skin
Animal bite
Through a puncture wound or sharing needles
24
Q
Give some examples of ingestion
A
Consuming contaminated food or drink
Transferring pathogens to the mouth from the hands
25
What is indirect transmission?
A pathogen that is transmitted indirectly from one individual to another
26
How can pathogens be indirectly transmitted between animals?
Fomites
Droplet infection
Vectors
27
Give some examples of Fomites
Inanimate objects such as bedding, socks, cosmetics can transfer pathogens
28
Give some examples of droplet infection
Droplets of saliva and mucus which are expelled from the mouth when talking, coughing or sneezing.
These droplets can spread to healthy individuals if inhaled
29
Give some examples of vectors for animals
Other animals/ insects
Water
30
What factors can affect the transmission of communicable diseases in animals?
-Overcrowded living and working conditions
-Poor nutrition
-Compromised immune systems
-Poor disposal of waste
-Providing breeding sites for vectors
-Climate change (this can introduce new vectors and new diseases)
-Culture and infrastructure
-Socioeconomic factors- lack of trained health professionals and insufficient public warning.
31
How can pathogens be directly transmitted between plants?
Pathogens are spread between plants when a healthy plant comes into direct contact with a diseased plant.
32
How can pathogens be indirectly transmitted between plants?
Soil contamination
Vectors
33
Give some examples of soil contamination
Infected plants often leave pathogens or reproductive spores from Protoctista or fungi in the soil which can then infect the next crop.
34
Give some examples of vectors that transmit disease between plants
Wind- bacteria, viruses or spores can be carried in the wind between plants
Water- Raindrops can carry pathogens and spores
Animals- insects and birds carry pathogens and spores between plants
Humans- pathogens and spores can be transmitted by hands, clothing, farming practices and transportation.
35
What factors can affect the transmission of communicable diseases in plants?
- Planting varieties of crops that are susceptible to disease
- Overcrowding increases the risk of contact
- Poor mineral nutrition
- Damp, warm conditions increase the survival and spread of pathogens and spores
- Climate change- changing conditions allow animal vectors to spread disease and changing rainfall and wind promote transmission.
36
What are physical defences in plants?
Barriers that prevent microorganisms from entering plant tissue
37
What are chemical defences in plants?
Substances secreted by the plant that kill microorganisms
38
How do plants respond to attack from pathogens?
Receptors in the cell walls respond to chemicals that are produced when the cell wall is attacked or chemicals produced by the pathogen.
Receptors respond by releasing signalling molecules which switch on genes in the nucleus
This triggers cellular responses:
- either the production of defensive chemicals which trigger defences in unaffected cells
- or by physically strengthening cell walls.
39
What are the physical defences of a plant?
-Waxy cuticle which acts as a barrier and prevents pathogens from coming into direct contact with epidermal cells
-Cell walls composed of cellulose
-Production of Callose
40
Describe the role of Callose
Callose provides a physical barrier within plants to prevent the spread of a pathogen.
Callose is deposited between the cell walls and cell membranes next to infected cells, as well as depositing itself in the plasmodesmata of adjacent cells to the site of infection to prevent further spread.
Lignin can then be added to Callose in order to strengthen the barrier formed.
Callose also blocks the sieve cells of the phloem reducing spread of the pathogen around the plant.
41
What are the Chemical defences of plants?
-Insecticides
-Insect Repellents
-Cyanide
-Antibacterial compounds
-Anti fungal compounds
-Anti-oomycetes
42
How do Insecticides work in plants?
Plants naturally produce chemicals (such as nicotine or caffeine) to kill off insects as well as insect eggs and their larvae.
43
How does insect repellent work in plants?
Insect repellents repel the insect vector that carry disease, for example extracts that come from lemon grass repel mosquitoes.
44
How is cyanide produced in plants?
Plants can make chemicals that can be broken down to produce cyanide compounds when the plant is under attack.
45
How do antibacterial compounds work in plants?
Plants produce antibacterial chemicals compounds that kill off bacteria such as phenols (antiseptics)
46
How do anti-fungal compounds work in plants?
Plants produce chemicals that kill fungi by producing enzymes such as chitinase which breaks down the chitin cell wall of Fungi.
47
How do Anti-oomycetes work in plants?
Plants can produce enzymes such as Glucanases which break down Glucan found in the cell walls of oomycetes in order to kill off oomycetes.
48
What are Non-specific defences?
Defends against all pathogens in the same way
49
What are the non-specific defences that animals use to defend against pathogens?
Skin
Mucous membranes
Blood clotting
Wound repair
Inflammatory response
Expulsive reflexes
Phagocytosis
50
How does skin act as a non-specific defence barrier in animals?
Physical barrier, blocking the entry of pathogens into the body.
Chemical barrier, producing chemicals which are antimicrobial and can lower pH inhibiting the growth of pathogens.
51
How do Mucous membranes act as a non-specific barrier in animals?
Mucous membranes protect body openings which are exposed to the environment by secreting a sticky mucus that traps pathogens and contains lysosomes which break down bacterial and fungal cell walls.
52
How do expulsive reflexes act as a non-specific defence mechanism in animals?
Coughing and sneezing expel pathogen from mucus in the gaseous exchange system.
While vomiting expels contents of the gut along with the infected pathogens.
53
How does blood clotting act as a non-specific defence barrier in animals?
Blood clots seal open wounds to prevent pathogenic entry. When platelets are exposed to damaged blood vessels they convert soluble fibrinogen into insoluble fibrin which results in the formation of a fibrin mesh that traps platelets and red blood cells forming a clot.
The clot then dries out forming a scab
54
How does the inflammatory response act as a non-specific barrier in animals?
The inflammatory response results in swelling, heat, pain and redness around the damaged tissue. This is because the tissue releases molecules which increases the permeability of blood vessels forcing tissue fluid out into the surrounding area which causes swelling.
The molecules also cause vasodilation of the blood vessels, increasing blood flow to the infected area and raising the temperature preventing pathogens from reproducing. This also attracts more white blood cells to the site of damage to dispose of pathogens by phagocytosis.
55
How does wound repair act as a non-specific defence mechanism in animals?
The skin is able to repair itself in the event of injury, the surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. This tissue below the wound then contracts bringing the sides closer together to be repaired by collagen fibres.
56
What are phagocytes?
Specialised white blood cells that carry out a non-specific immune response by engulfing and destroying pathogens via phagocytosis.
57
What are the two types of Phagocyte white blood cells?
Neutrophils and Macrophages
58
What is the difference between Neutrophil and Macrophage?
Neutrophils are the first to respond to pathogens inside the body and move towards the wound in reponses to signals from cytokines (messenger molecules) which are released by cells at the site of the wound.
Macrophages acts as an antigen presenting cell by presenting the pathogens antigens on its surface to activate other immune system cells.
59
Describe the stages of Phagocytosis
Pathogens produce chemicals that attract phagocytes
Phagocytes recognise the foreign antigens on the pathogen as non self
The cytoplasm of the phagocyte moves around the pathogen, engulfing it. This is made easier by the presence of opsonins.
The pathogen is then contained within a vesicle known as a phagosome in the cytoplasm of the phagocyte
A lysosome fuses with the phagosome and releases hydrolytic enzymes which break down the pathogens.
60
What are opsonins?
Protein molecules that act as a type of antibody by attaching to the antigen on the surface of a pathogen. Therefore, aiding phagocytosis by marking the antigen to trigger an immune response or marking dead cells for recycling.
61
What cells acts as antigen presenting cells?
Macrophage and Dendritic cells
62
What are antigen presenting cells?
Following phagocytosis the pathogens antigens are retained and then presented onto its protein complex on the surface of the cell.
63
What are Cytokines?
Chemical produced by phagocytes that have engulfed a pathogen.
Cytokines act as cell signalling molecules by activating and stimulating other phagocytes to move to the site of infection.
64
What is the specific immune system?
The Immune system is familiar with the antigen after the initial response therefore leading to a more rapid response during susbsequent encounters
65
Describe the structure of antibodies
-Y-shaped glycoproteins called immunoglobulins.
-Made up of two identical polypeptide chains known as the heavy chains and two shorter identical chains known as the lighter chains.
-The chains are held together by disulfide bridges which hold the lighter and heavier chains together -More disulfide bridges in the polypeptide chains holding their shape
-Antigen binding site is known as the variable region while the rest of the antibody is known as the constant region.
66
What is the function of the variable region on an antibody?
The variable region on the antibody is complementary to a specific antigen of a pathogen or toxin that has triggered an immune response.
67
What is the function of the hinge region on an antibody?
Provides the molecule with flexibility so it is able to bind with two separate antigens.
68
What structure is formed when an antibody binds to an antigen?
Antigen-antibody complex
69
Describe how antibodies are able to defend against pathogens
-When an antigen-antibody complex is formed, the antibody acts as an opsonin so the complex can be engulfed and digested by phagocytes
-Pathogens are unable to invade hosts cells once they are part of the antigen-antibody complex as the antibodies block the receptors that the pathogens use to bind to host cells.
-Agglutinating pathogens, antibodies can bind to two pathogen at any one time therefore causing the pathogens carrying the antigen-antibody complexes to clump together. Therefore, preventing the spread of pathogens in the body and making it easier for the phagocyte to engulf a number of pathogens at the same time.
- Neutralise toxins, binding to toxins produced by pathogens so they become inactive and can no longer affect human cells.
70
What are T lymphocytes?
Originate as a precursor cell in bone marrow, however migrate to the thymus gland where they differentiate into several types of T lymphocytes.
They are involved in the specific immune response.
71
What are the main types of T lymphocytes?
T helper cells
T killer cells
T memory cells
T regulator cells
72
What is the role of T helper cells?
Release interleukin (type of cytokine) in a form of cell signalling which stimulates other T cells to differentiate as well as stimulating B cells to mature and develop.
73
What is the role of T killer cells?
Destroy the pathogen carrying the antigen.
They produce a chemical, perforin, which kills the pathogen by making holes in the cell membrane so it is freely permeable.
Receptors of the T killer cells which are complementary to the antigens of the pathogen can bind releasing cytotoxins that trigger apoptosis.
74
What is the role of T memory cells?
Part of the immunological memory, if they meet an antigen a second time, they divide rapidly forming clones of the T killer cells that destroy the pathogen.
75
What is the role of T regulator cells?
Suppresses the immune system by controlling T cells to stop them recognising own self antigens as foreign
76
What are the main types of B lymphocytes?
Plasma cells
B effector cells
B memory cells
77
What is the role of plasma cells?
Produce antibodies to a particular antigen and release them into circulation.
78
What is the role of B effector cells?
Inactive form of plasma cell which then divide to form plasma cell clones
79
What is the role of B memory cells?
Part of the immunological memory.
Remember a specific antigen enabling the body to respond quickly following a second encounter.
80
What is Cell mediated immunity?
T lymphocytes respond to altered cells- APC or cancer
81
Describe the process of Cell mediated immunity
Receptors on some of the T helper cells are complementary to the antigens of APC.
This activates the T helper cells and produces interleukins, stimulating more T cells to divide by mitosis.
The cloned T cells may:
-develop into T memory cells
-produce interleukins stimulating phagocytosis or the division of B cells
-develop into T killer cells
82
What is Humoral immunity?
B lymphocytes respond to antigens on antigen MHC complexes of APC and free pathogens
83
Describe the process of Humoral immunity
Colonal selection- B cells with complementary antibody will bind to the pathogen and engulf it
The B cells become B-APC and present the antigen- antibody complex on its cell surface membrane
T helper cells recognise the B-APC and bind to the antigen-antibody complex, releasing interleukins to signal colonal expansion where the B-APC differentiate and divide into plasma cells to produce many specific antibodies or B memory cells to prepare for a secondary response of the same pathogen
84
What is colonal selection?
Exposure to a specific antigen stimulates the division of the cell with the appropriate antibody.
85
What is the primary immune response?
The immune response that occurs when a pathogen enters the body for the first time, the antigens on its surface activate the immune system.
The response is slow as there are not enough B lymphocytes that make the antibody needed to bind to it, during this time the individual will show symptoms of the disease.
86
What cells are formed following the primary immune response?
Memory T lymphocytes - remember the specific antigen
Memory B lymphocytes - record the specific antibodies needed to bind to the antigen
87
What is the secondary immune response?
The immune response that occurs when the same pathogen enters the body again.
The response is much quicker as clonal selection happens faster.
The pathogen are killed off quickly often before symptoms of the disease can be caused.
88
What cell is activated during the secondary immune response?
Memory B lymphocytes divide into plasma cells which produce the right antibodies.
89
What type of pathogen causes Ring worm?
Fungi (affects mammals, including humans)
90
Describe the role of the lymphatic system in the defence mechanism of the body
Lymph vessels contain lymph nodes consisting of lymphocytes that produce and release antibodies.
Lymph nodes can also intercept bacteria which are then engulfed by phagocytes found in the nodes.
Enlarged lymph nodes are signs that the body is fighting off infection.
91
What is an autoimmune disease?
The immune response of an organism against its own healthy cells
92
What is an autoantibody?
Antibody produced by the immune system that is directed to an individuals own protein
93
Give some examples of autoimmune diseases
Type 1 diabetes
Rheumatoid arthritis
Lupus
94
Describe how arthritis acts as an autoimmune disease
The body produces antibodies which attack tissues of the joints
95
What is natural active immunity?
Immunity that results from the response of the body to the invasion of a pathogen through normal life processes.
The body responds through the differentiation of naive B cells into memory B cells or plasma cells to produce its own antibodies during a primary or secondary response.
96
What is natural passive immunity?
The immunity given to an infant by the mother through the placenta or the colostrum.
This lasts until the immune system of the baby begins to make its own antibodies.
97
What is artificial passive immunity?
Immunity that results from the administration of antibodies from another animal against a dangerous pathogen.
For example, Tetanus
98
What is artificial active immunity?
Immunity which results from the exposure to a safe form of pathogen, often in form of a vaccination which is injected into the bloodstream.
99
State the different ways in which a pathogen can be made safe
The pathogen is made safe by:
-inactive form of pathogen
-weakened strains of pathogen
-toxins have been detoxified
-isolating antigens
-genetically engineered antigens
100
How can epidemics of a disease be prevented?
Mass vaccination of the population provides herd immunity protecting against the infectious disease.
101
What is herd immunity?
When a large percentage of the population has become immune to the infection as a result of vaccination or through natural active immunity therefore becoming protected against the infectious disease.
102
Give an example of two communicable diseases that cannot be prevented by vaccination
Malaria- the plasmodium Protoctista ‘hides’ inside the erythrocytes so is protected from the immune system
HIV suppresses the immune system
103
Describe how a vaccine is used to provide artificial active immunity
Firstly, the pathogen is altered for safe use
Then small amounts of the safe antigen is injected into the blood
Primary immune responses is triggered- body produced antibodies and memory cells
If the vaccinated individual comes into contact with the live pathogen, a secondary immune response is triggered and the pathogen is destroyed before symptoms are suffered.
104
State some natural sources of medicines
Penicillin drug- extracted from mould and acts as an antibiotic
Aspirin drug - extracted from willow bark and acts as a pain killer
Digoxin drug- extracted from fox gloves to treat heart problems
105
Describe the importance of maintaining biodiversity for medicinal purposes
Ensure that plants, animals and microorganisms do not become extinct which once researched could produce a life saving drug.
106
What is meant by a personalised medicine?
A combination of drugs that work with an individuals combination of genetics and disease.
This allows disease to be treated more specifically.
107
What is Pharmacogenetics?
Where drugs are specialised to suit a specific individual and their condition by analysing their genes.
108
What is synthetic biology?
Re engineering biological systems for new purposes in medicine.
109
What is selective toxicity?
Antibiotics affect the metabolism of bacteria without affecting the metabolism of human cells.
110
What is meant by antibiotic resistant bacteria?
Bacteria that have developed a mutation to become resistant to antibiotics.
Therefore, the bacteria are able to survive and reproduce giving rise to the population of antibiotics resistant bacteria.
111
What is the problem of antibiotic resistant bacteria?
The bacteria are evolving faster than the development of antibiotics
112
State two examples of antibiotic resistance bacteria
MRSA
C. Difficile
113
State how antibiotic resistant bacteria can be reduced
-antibiotics only prescribed when needed
-patients must finish the entire course of antibiotics
-introduce infection control in hospitals
114
Outline the processes that lead to the production of antibodies against an unfamiliar bacterium.
The B cells carry the antibody to one antigen
The activated B cells divide by mitosis
The B cell differentiates into plasma cells and secretes antibodies complementary to the antigen.
