Unit 4.1.1 - 4.1.2 Defining Disease & Infectious Diseases Flashcards
1
Q
What is the WHO definition of health?
A
A state of complete physical, mental and social well being which is more than just the absence of disease.
2
Q
What percentage of British people claim to be completely healthy at any one time?
A
Less than 10%
3
Q
Health is difficult to measure, therefore non-health is easier to quantify, what is this usually referred to as?
A
Disease. Which can be minor, chronic or major or a combination of these. A disease is a diagnostic label which is given to a set of symptoms by a HP.
4
Q
What is dysphoria?
A
General feeling of dissatisfaction with ones life.
5
Q
What is a physical illness?
A
A physical illness affects the body, with symptoms which may be associated with a particular organ system or more generally throughout the body - they vary in severity from the trivial to those which regularly cause death.
6
Q
What is a mental illness?
A
A disorder of thought, mood or behaviour that causes distress or impaired functioning, also referred to as psychiatric disorders. Including anxiety disorders such as panic disorder, agoraphobia, OCD, or post traumatic stress disorder, affective (mood) disorders such as depression or bipolar: personality disorders and schizophrenia.
7
Q
What are the different causes of disease?
A
Infection, allergies, injuries, degenerative autoimmune and metabolic conditions, congenital problems, genetic disorders and degenerative disorders.
8
Q
What are infectious diseases?
A
Such as the common cold or measles are infectious (communicable) which means they can be passed from one person to another.
9
Q
What are non-communicable diseases?
A
Such as heart disease or depression, this means they affect one individual but cannot be passed on to another.
10
Q
What is an infectious disease caused by the invasion of?
A
A pathogen.
11
Q
What is a pathogen?
A
An organism which is capable not only of invading our bodies but also of causing the symptoms of disease. Most are micro-organisms - bacteria, viruses, fungi or protists but some are bigger lie threadworm or tapeworm.
12
Q
What do pathogens do in or on the body of the host?
A
Rapidly reproduce.
13
Q
How can an infectious disease cause the symptoms of disease?
A
The invading micro-organism often causes tissue damage when invading or produces a toxin and it is the effects of the toxin which causes the symptoms of disease.
14
Q
What is our body flora?
A
The microorganisms that colonise both the inside and outside of our bodies which do not cause disease but help us by aiding digestion, competing with pathogens, even producing chemicals which are toxic to pathogens.
15
Q
What are the 5 main groups of pathogens that cause disease?
A
Viruses, Bacteria, Fungi, protists and Metazoa (usually worms)
16
Q
What is the simple structure of a virus like?
A
Viruses are very small with a very simple structure.
17
Q
What do viruses contain?
A
A piece of genetic material, some enzymes needed for replication (internal viral proteins) and an ouster case of structural proteins called the capsid.
18
Q
What can the genetic material of a virus be?
A
It can be DNA or RNA. Either double or single stranded.
19
Q
What is the structure of the capsid?
A
The capsid is often very regular and geometric in shape, capsomeres are the repeating protein unit that make up the capsid. The capsid can also have viral proteins attached, often used in attachment to the host cell. There can also be an extra coat called the envelope (made from host cell membrane).
20
Q
Although viruses can last for years in air, what makes them total parasites?
A
They are incapable of replication unless they are inside a host cell.
21
Q
What are bacteriophages?
A
Viruses which infect bacteria, these are used by scientists to study the action of viruses.
22
Q
What happens when a viruses attaches to a host cell?
A
The viruses genetic material is injected into the host cell.
23
Q
In the lysogenic pathway, what happens once the viruses genetic material is injected into the hot cell?
A
The viral DNA is incorporated into the host cell DNA and the viral DNA is replicated without hard every time the bacterium divides. This pathway can then change to join the lytic pathway.
24
Q
In the lytic pathway, what happens once the viruses genetic material is injected into the host cell?
A
The viral DNA inactivates the host DNA and hijacks the cell biochemistry. The virus uses the cell to replicate its DNA, the cell creates new viruses from the viral DNA as well as synthesising and release the enzyme lysozyme.
25
What does the enzyme lysozyme do?
The lysozyme breaks down the cell, causing it to burst and release up to 1000 viruses that go on to infect other host cells.
26
Why are viral infections difficult to treat?
Because the virus reproduces inside living cells - to destroy the virus the cell must also be destroyed.
27
What do antiviral medicines, such as those used to treat HIV/AIDs do?
They aim to stop the virus infection new cells and prevent the virus from spreading.
28
What makes viruses very specific to particular tissues?
Viruses bind to particular cell markers on the surface of host cells - each type of cell has its own recognition markets and certain viruses only bind to specific markers - this is one way in which scientists may be able to prevent or cure viral diseases in the future.
29
What are the most numerous type of organism on the planet?
Bacteria.
30
What type of organism are bacteria?
Single celled prokaryotic organisms.
31
What is the size range of a bacterium?
No bigger than 10 micrometers and range in size. 80 million bacteria could be linked up across the diameter of a one pound coin.
32
What do bacteria contain in terms of genetic information?
The genetic material is not contained in a nucleus like in eukaryotic organisms. They have their own main singular circular strand of DNA - its genome and may also have one or more smaller circular DNA plasmids. The plasmids code for aspects of the bacterial phenotype such as the production of a particular toxin or resistance to a particular antibiotic.
33
How are viruses different from bacteria?
Bacteria live and replicate independently - they do not need to be inside the cell of another organism to reproduce.
34
Many types of bacteria are positively beneficial to humans and other life forms - they place a vital role in the environment as what?
Decomposers for example.
35
Many bacteria live in the guts of animals and help them to digest their food - who is this particularly important in?
Herbivores
36
In a healthy human being what weight of bacteria in their digestive system alone?
Around 2kg.
37
What are some bacterial diseases?
Tuberculosis, pneumonia, cholera, salmonella and capylobacter food poisoning and gonorrhoea.
38
All bacteria have a cell wall, what does this prevent and maintain?
The cell wall prevents the bacterial cells swelling and bursting and maintains the shape of the bacterium and gives support and protection to the contents of the cell.
39
The contents of bacterial cells means that they are usually hypertonic to the medium around them, what does this mean?
Water tends to move into the cells by osmosis.
40
What is within the bacterial cell wall?
The cell membrane.
41
What is the cell membrane the site of and why?
Bacteria have no mitochondria so the cell membrane is also the site of some of the respiratory enzymes, the structure and function is very similar to the membranes of eukaryotic cells other than this.
42
What do some bacteria have around their cell walls?
Capsules or slime layers.
43
What does the capsule do for the bacteria?
The capsule protects the bacteria from phagocytosis by the WBCs and also prevents its antigens from activating a response in the host immune system. In this way a capsule makes it easier for a bacterium to be pathogenic yet many capsulated bacteria do not cause disease.
44
What does it seem that capsules evolved originally to help bacteria do?
Survive very dry conditions.
45
Another structural feature seen in some bacteria are pili, threadlike proteins sticking out from the surface of the bacteria - what do these do?
They seem to be useful for attachment to a host cell, for binding to specific antigens and for sexual reproduction in bacteria - they can also make bacteria more vulnerable to viral infections as bacteriophages can use pili as an entry point to the cell - bacteria with pili include E/coli and Salmonella.
46
Some bacteria cannot move themselves actively they are dependent on air and water current or the actions of other organisms to get around - what do other species have to help them move towards stimuli?
Tail like flagella to move towards stimuli such as light and dissolved food and away from poor conditions or toxins.
47
How do the flagellum make the bacteria move?
The flagellum rotate rapidly to propel the bacterium - about 100 revolutions per second.
48
Bacterial cell walls surround the plasma membrane, what do they cell walls comprise of?
They comprise a layer mainly consisting of peptidoglycan.
49
What is peptidoglycan made up of?
Many parallel polysaccharide chains with short peptide cross linkages forming an enormous molecule with a net like structure.
50
What is Gram Staining?
A staining technique developed by Christian Gram in 1884. It involves a blue/purple stain (crystal violet) and a red stain called safranine. It is used to distinguish between gram positive and gram negative bacteria.
51
What are the walls of gram positive bacteria?
They have 2 basic layers, the plasma membrane and a thick layer of peptidoglycan - containing chemicals such as teichoic acid within its net like structure.
52
What is the result of gram staining on gram positive bacteria?
The crystal violet binds to the trichroic acid and resists subsequent decolourising with an ethanol/ethanone mixture - as a result it does not take up any red safranine dye which follows giving bacterial cells a positive blue purple colour under the light microscope e.g. MRSA.
53
What is the structure of the cell call of a Gram-negative bacteria?
They have three basic layers - the plasma membrane, a thinner layer of peptidoglycan with no teichoic acid and then an outer membrane like layer made up of lipopolysaccharides.
54
What is the result of gram staining on Gram-negative bacteria?
Little crystal violet binds to the cell wall and any which does is readily decolourised by ethanol/ethanone mixture and replaced with reddy, so they appear red under the light microscope. E.g. salmonella sap and helicobacter.
55
Grouping bacteria simply by Gram staining is of limited use in classifying the different types - what is another way bacteria can be identified?
By their shape.
56
What are the different shapes of bacteria?
Spherical (cocci), Bacilli (rod-shaped), Twisted (spirilla) or comma-shaped (vibrios)
57
Bacteria can also sometimes be grouped by their respiratory requirements, what is an obligate aerobe?
Obligate aerobes need oxygen for respiration.
58
What is a facultative anaerobe?
Use oxygen if it is available but can manage without it.
59
What is an obligate anaerobe?
Can only respire in the absence of oxygen.
60
When bacteria get into the body, where will they often grow? but what can happen?
In a localised area, unless they get nto the bloodstream when they can be carried all around the body.
61
How do bacteria most often make people unwell?
Because of the toxins they produce, either as a by product of their metabolism or in order to incapacitate the host or its immune system.
62
What two things can toxins be classified as?
Endotoxins and Exotoxins.
63
What are endotoxins?
These are lipopolysaccharieds, part of the outer layer of gram-negative bacteria.
64
What do endotoxins cause?
They are rarely fatal in themselves and tend to cause symptoms such as fever, vomiting and diarrhoea - such symptoms can still lead indirectly to death, for example by dehydration.
65
What are exotoxins?
Exotoxins are usually soluble proteins such are produced and released into the body by bacteria as they metabolise and reproduce.
66
What effects do exotoxins have?
There are many different types and they tend to have specific effects - some damage cell membranes causing cell breakdown or internal bleeding, some act as competitive inhibitors to neurotransmitters while other directly poison cells.
67
What do exotoxins cause?
They rarely cause fevers but they include some of the most dangerous and fatal bacterial diseases - for example clostridium botulinum produces botulinum toxin, one of the most toxic substances known to man - - estimated 1mg pure toxin could kill one million guinea pigs.
68
What are bacerial diseases cured by?
Using antibiotics and also vaccinations to prevent us getting serious bacterial diseases.
69
Most bacteria are not harmful to humans as they live on and digest dead plants and animals - what is this vitally important for?
To help recycle nutrients that would otherwise be locked up in organisms after they have died.
70
How can humans use these useful bacteria?
In the treatment of sewage or other wastes, as well as for making products like cheese and yogurt.
More recently bacteria have been used in biotechnology to produce useful chemicals and medicines. Human insulin is produced by genetically engineered bacteria and the enzymes found in biological washing powders are also produced by bacteria.
71
What are fungi?
They are eukaryotic organisms, frequently multicellular.
72
What are most of the many thousands of fungi?
Not human pathogens!
73
Fungi are heterotrophic, what does this mean?
They digest food extracellularly and then reabsorb it.
74
What are common types of fungi?
Mushrooms, toadstools and bread mould.
75
What do individual fungal cells have?
A nucleus, cell wall and mitochondria-like structures in their cytoplasm.
76
What are many fungi's body structure made up of?
Tangled threads forming a mycelium, but some, like the yeasts are unicellular!
77
What do fungi play a vital role in?
Decomposing dead material and recycling the nutrients to make them available for the growth of other plants.
78
Which fungi grows as individual cells and has been used in the production of beer, wine and bread?
brewers and bakers yeast.
79
What has the fungus Penicillium notatum provided us with?
Produced the antibiotic penicillin.
80
What are the fungi that often cause human disease, where do these infect?
Dermophytes, infecting the skin, hair, nails and causing diseases such as athlete's food, ringworm, oral and vaginal thrush
81
How do fungi cause infection and damage?
The fungal hyphae grow in the upper layers of the skin.
82
Where can some rare fungi cause fatal infections?
Brain, the valves of the heart and other organs
83
Which patients can the rarer fungal infections cause severe problems?
In immunocompromised patients such as people undergoing cancer treatment and people affected by AIDs.
84
What are Protists?
Single celled eukaryotic organisms
85
What are spore forming, flagellates, amoeboid and ciliates types of?
Protists.
86
Different type of protists share the same features, what are these?
Cell membranes, cytoplasm, vacuole and nucleus.
87
How are protists able to get food?
They are able to move and get food by engulfing smaller microbes or cells.
88
What are vectors?
Vectors transmit the protist from one host to another as many of these organisms have life cycles which involve a number of different hosts and environments.
89
What are the vectors mostly, but not always for protists?
Insects.
90
What are examples of diseases caused by protists?
Malaria, toxoplasmosis and giardia.
91
Who is infection by protists usually spread?
By structures called cysts which are cells that have secreted a protective later around them so that they can survive the journey from one host to the next
92
What are cysts?
Cells that have secreted a protective later around them so that they can survive the journey from one host to the next
93
Once inside the new host, what do these cysts do?
They develop into the active protists which grow, reproduce and cause symptoms of disease in the new host
94
What are common infections caused in humans by protits?
Amoebic dysentery, sleeping sickness and malaria.
95
What is the name for an organism which lives on or in another organism, gaining benefit from it and providing nothing in return?
A Parasite.
96
What makes a really successful parasite?
A parasite which does the minimum damage to its host whilst gaining maximum benefit itself.
97
What are metazoans?
Complex multi-cellular animals which develop organ systems of their own.
98
What is the type of metazoans which almost always act as humans pathogens?
Helminths (worms)
99
What are Helminths?
Disease causing worms which all act as internal parasites - people can be their only host or they may have complicated life cycles.
100
What diseases can helminths cause?
Helminth diseases range from relatively mild problems such as thread worm through to some of the most debilitating diseases of the developing world such as bilharzia and river blindness.
101
What factors are involved in whether a person catches an infectious disease?
Overall health, state of their immune system, diet, environmental factors and a pathogens virulence.
102
What does virulence mean?
Virulence is the power of a pathogen to cause severe disease - example being flu - the virus is constantly changing slightly producing different strains of flu, some are relatively mild but other strains are very virulent causing severe disease with a high proportion of deaths among those infected.
103
What is a communicable disease?
This means that the infection is capable of spreading from one person to another.
104
What will the likelihood of any particular infectious disease being passes from one person to another depend on the interaction between?
The pathogen, the host and the environment.
105
How does airborne/droplet infection transmission occur?
When we cough, sneeze, talk or breathe, millions of tiny droplets are expelled from our respiratory system. If infected these droplets can contain pathogens which someone else can breathe into their body or can land on an open wound e.g. influenza, tuberculosis, measles.
106
How does direct contact transmission occur?
Direct physical contact with an infected individual - many sexually transmitted diseases are spread this way e.g impetigo, gonorrhoea and syphilis.
107
How does ingestion of contaminated food or water transmission occur?
Ingestion of contaminated food or water transfers pathogens directly into the digestive system. e.g diarrhoea, cholera, salmonella, hepatitis A.
108
How does inoculation/break in the skin transmission occur?
A pathogen can get directly into the bloodstream through a break in the skin, a needle or an animal bite. e.g. Hepatitis B, AIDS, rabies, tetanus.
109
How does inanimate objects infection transmission occur?
Inanimate objects such as towels, bedding and toys can carry pathogens from one person to another. eg. Staphylococcus infection.
110
How does vector transmission occur?
A living creature which transmits infection from one host to another. Many vectors are insects or other arthropods such as the Anopheles mosquito which carries malaria. e.g. malaria, dengue, yellow fever, bilharzia.
111
What factors regarding a pathogen affect the likelihood of a disease spreading?
- virulence
- infectiousness
- ability of the pathogen to adapt to different environmental conditions and the
- way it responds to antibacterial drugs and the immune response.
- the way the host behaves.
112
Which factors increase risk of infection?
- Travel to countries whre particular diseases are endemic.
- Irresponsible sexual behaviour
- Doctors and nurses
- Crowded living conditions, poor hygiene, poor nutrition, underlying diseases
113
What can greatly reduce the risk of infection by a pathogen?
Vaccination or if someone has been infected by it before.
114
What is known as pathogenicity?
The success of a pathogen - its ability to survive as well as possible and therefore in human terms its ability to cause disease.
115
Survival outside or between hosts is also important as many micro-organisms are killed by drying, UV light and extreme heat or cold - what is a common way bacteria overcome this?
They form very hardy spores which can withstand extreme conditions for many years.
116
Pathogens are vulnerable at the point when they pass form one host to another because if they do not find another host they may die? what are some specialised methods of spreading?
- Being enclosed in droplets which are passed out the body in coughs and sneezes.
Delicate bacteria like gonorrhoea which cannot survive outside the host so are passed on directly through moist mucous membranes during sex.
117
Attachment to the host can be a problem, how do some large pathogens and micro organisms overcome this?
Large pathogens like helminths often have very specialised body body, hooks, jaws or suckers which keep them attached to their host.
- E.coli overcome flushing action of urine by attaching to the epithelium of the UT using specialised fimbria.
118
Some micro-organisms can defend themselves against the immunological response launched by their host and these have a particular advantage and are likely to be very successful pathogens, what are some examples of this?
Bacterial capsules can act as a defence against the antibodies produced by some of their hosts, others like mycobacterium tuberculosis colonise the hosts phagocytes to help in their own life cycle and some have specialised biochemistry to help overcome any host reaction.
119
Most immune system respond to infection by recognising the antigens on the surface of a pathogen as foreign and producing antibodies against it, therefore what is an efficient way of avoiding the hosts immune system?
For a pathogen to constantly change the surface antigens, as people have reduced or even no immunity to these new strains.
E.g. Trypanosomes which cause sleeping sickness change surface antigens every few days. Or Flu.
120
Some micro-organisms have a very high pathogenicity because they actually suppress the activity of the host's immune system - what does this mean for the pathogen and host?
The pathogen are free to reproduce and invade host cells but the host will be open to other infections as well - a suppressed immune system cannot fight any invading pathogen. E.g African trypanosomiasis and HIV/AIDs are immunosupressant pathogens where the patient is often attacked by other microbes due to the ineffectiveness of the suppressed immune system.
121
What can many micro-organisms produce which affects the pathogenicity?
Toxins - these are frequently responsible for the symptoms of disease although usually produced as a necessary part of the microbes metabolism and the fact they are toxic to humans is incidental.
