Topic 4 - Response to Infection Flashcards
(129 cards)
1
Q
What is an infectious disease?
A
A disease caused by a pathogen that can be transferred from one organism to another, either directly or indirectly.
2
Q
What is a pathogen?
A
Is a disease-causing organism, such as a bacterium or virus, that can invade the body and disrupt normal bodily functions.
3
Q
What is bacteria?
A
Are unicellular, prokaryotic organisms without membrane-bound organelles.
4
Q
Where can bacteria be found?
A
- In the environment (soil, water, air)
- On human skin (armpits)
- In the alimentary canal (intestines – aiding digestion)
- In fermented food production (yoghurt, cheese).
5
Q
What is a key disease mechanism of bacteria?
A
Bacteria can cause disease by:
- Producing toxins that damage and destroy host cells.
- Inducing allergic responses or inflammatory immune responses.
- Directly invading tissues, leading to inflammation or damage.
6
Q
What is the structure of the slime layer in bacteria?
A
External layer that helps protect bacteria and aid in adhesion.
7
Q
What is the structure of the capsule in bacteria?
A
Thick protective carbohydrate layer aiding in immune evasion (protecting bacteria from phagocytosis).
8
Q
What is the structure of the cell wall in bacteria?
A
Provides structure and protects the cell; made of peptidoglycan.
9
Q
What is the structure of the cell membrane in bacteria?
A
Regulates entry/exit of substances into the cytoplasm.
10
Q
What is the structure of the cytoplasm in bacteria?
A
Gel-like fluid with ribosomes (site of chemical processes) but no membrane-bound organelles.
11
Q
What is the structure of DNA in bacteria?
A
Single circular chromosome and plasmids (no nucleus).
12
Q
What is the structure of flagella in bacteria?
A
Tail-like structures enabling mobility (not present in all bacteria).
13
Q
What is the structure of ribosomes in bacteria?
A
Sites of protein synthesis (not membrane bound).
14
Q
How is bacteria classified?
A
- By shape
- By gram staining
- By oxygen requirement
15
Q
What are the different shapes of bacteria?
A
- Cocci
- Bacilli
- Spirilla
- Vibrio
16
Q
What is the cocci shape? Provide an example.
A
Spherical (Staphylococcus).
17
Q
What is the bacilli shape? Provide an example.
A
Rod-shaped (Lactobacillus).
18
Q
What is the spirilla shape?
A
Spiral-shaped.
19
Q
What is the vibrio shape?
A
Comma-shaped.
20
Q
What is gram staining?
A
Is a differential staining technique used to classify bacteria into two groups:
- Gram-positive
- Gram-negative
based on their cell wall composition.
21
Q
In gram staining, what colours indicate positive and negative?
A
- Gram-positive = purple
- Gram-negative = pink
22
Q
How does bacteria cause infections?
A
- Enter the body via breaks in skin, mucous membranes, ingestion.
- Multiply rapidly
- Release toxins or trigger immune response
- Can cause tissue damage or illness depending on the type of bacteria.
23
Q
What is a virus?
A
Are non-living infectious agents much smaller than bacteria. Viruses cannot reproduce by themselves; they must invade a host cell to replicate.
24
Q
What are key disease mechanism of viruses?
A
- Attach to specific receptor sites on host cells
- Inject their genetic material into the cell
- Use the host cell’s machinery to replicate themselves (virus particles)
- Damage or destroy the host cell during the process as new viruses exit.
- This leads to symptoms specific to the type of tissue infected
25
What is nucleic acid in the structure of viruses?
DNA or RNA (never both) – genetic material.
26
What of the protein coat in the structure of viruses?
Also called capsid – protects the genetic material.
27
What is the lipid envelope in the structure of viruses?
Present in some viruses (e.g HIV, influenza) derived from host cell membrane
28
What is bacteriophage?
Is a type of virus that infects and destroys bacteria. They inject their DNA into the bacterial cell and replicate inside, often killing the host bacterium.
29
What is the lyctic cycle?
1. Virus attaches to host cell
2. Injects its DNA/RNA
3. Host cell replicates viral components
4. New viruses assemble
5. Cell bursts (lysis) and releases viruses
6. Rapid destruction of host cell.
30
What is direct contact?
It is the physical transmission of pathogens from an infected person to another through skin or bodily fluids.
31
What are the types of direct contact?
1. Skin to Skin Contact (Impetigo)
2. Sexual Contact (HIV, Chlamydia, Syphilis)
3. Contact with Blood (Hepatitis B via needlestick)
32
What is indirect contact?
When pathogens are transferred via intermediates (non-living objects or living organisms) instead of direct touch.
33
What are examples of some intermediates that transmit disease?
- Contaminated objects (fomites): Door handles, towels
- Air (droplets/airborne): Sneezing (COVID-19)
- Food or water: Salmonella
- Vectors: Mosquitoes (malaria), fleas (plague)
34
Why are barriers to infection considered the first line of defence?
They are non-specific and aim to prevent pathogens from entering the body in the first place as they operate continuously at the body’s surfaces, and they work before any infection occurs, reducing the need for internal immune responses.
35
What are the 3 types of barriers to infection?
1. Physical
2. Chemical
3. Microbiological
36
What is skin in terms of a physical barrier?
- First and most effective physical barrier.
- Composed of multiple tightly packed layers.
- Keratin makes it strong and waterproof.
- Sebum and sweat prevent microbial growth.
37
What are mucous membranes in terms of a physical barrier?
- Line body cavities that open to the outside (respiratory, digestive, reproductive tracts).
- Secrete mucus to trap pathogens and particles.
38
What is cilia in terms of a physical barrier?
- Tiny hair-like structures that beat rhythmically to move mucus and trapped particles to the throat.
- Found in respiratory passages.
39
What are eyelids and blinking in terms of a physical barrier?
- Protect the eye from dust and pathogens.
- Blinking spreads tears and clears debris.
40
What is meant by urine flow in terms of a physical barrier?
- Flushes out microorganisms from the urinary tract.
41
What is meant by saliva flow in terms of a physical barrier?
- Washes microbes and food debris from the mouth.
42
What are hairs (nose and ears) in terms of a physical barrier?
- Trap dust and microbes; together with mucus can trap up to 90% of inhaled particles.
43
What are lysozymes in terms of a chemical barrier?
- Enzyme that kills bacteria by breaking down their cell walls.
- Found in tears, saliva, sweat, nasal secretions, and tissue fluid.
44
What is stomach acid in terms of a chemical barrier?
- Strong hydrochloric acid (HCl) kills bacteria ingested with food or trapped in mucus.
45
What are vaginal secretions in terms of a chemical barrier?
- Naturally acidic to inhibit bacterial growth.
46
What is sweat and sebum in terms of a chemical barrier?
- Sweat contains salt and fatty acids, creating a hostile environment for microbes.
- Sebum contains antibacterial compounds.
47
What is urine (acidity) in terms of a chemical barrier?
- Slightly acidic and flushes out bacteria.
48
What is normal flora (microbiota) in terms of a microbiological barrier?
- Non-pathogenic bacteria live on the skin, gut, mouth, and urogenital tract.
- Compete with pathogens for space and nutrients.
- Produce substances (e.g. fatty acids) that inhibit growth of harmful microbes.
49
What are the two ways microflora protect us from pathogens.
1. Competitive Exclusion – Microflora take up space and nutrients that potential pathogens would need to survive.
2. Chemical Inhibition – They produce substances such as fatty acids or bacteriocins that inhibit the growth of harmful microorganisms.
50
What are the 4 protective reflexes?
1. Sneezing
2. Coughing
3. Vomiting
4. Diarrhoea
51
What is the stimulus for sneezing?
Irritation in the nasal cavity (dust, microbes).
52
What is the mechanism for sneezing?
Rapid expulsion of air through nose and mouth
53
How does sneezing prevent infection?
Removes mucus, microbes, and irritants from respiratory tract.
54
What is the stimulus for coughing?
Irritation in the lower respiratory tract (bronchi)
55
What is the mechanism for coughing
Forceful ejection of air from lungs.
56
How does coughing prevent infection?
Clears mucus and pathogens from airways.
57
What is the stimulus for vomiting?
- Psychological triggers
- Bacterial toxins
- Stomach stretching
58
What is the mechanism for vomiting?
Contraction of diaphragm and abdominal muscles.
59
How does vomiting prevent infection?
Expels contents of the stomach, removing ingested pathogens or toxins.
60
What is the stimulus for diarrhoea?
Irritation in intestines by bacteria, viruses, or protozoa.
61
What is the mechanism of diarrhoea?
Increased peristalsis moves material rapidly.
62
How does diarrhoea prevent infection?
Prevents absorption of pathogens and quickly eliminates them.
63
What are the 3 types of barriers?
1) Physical
2) Chemical
3) Microbiological
64
What are types of physical barriers?
- Skin
- Mucous Membranes
- Cilia
- Eyelids and Blinking
- Urine Flow
- Saliva Flow
- Hairs (Nose and Ears)
65
How does skin prevent infection?
- First and most effective barrier.
- Made of keratin which makes it strong and waterproof.
- Sebum (oily substance) kill bacteria.
- Sweat is slightly acidic and can kill bacteria.
66
How does the mucous membrane prevent infection?
- Lines body cavities (digestive, respiratory and reproductive tracts).
- Secrete mucus to trap pathogens and particles.
67
How does cilia prevent infection?
Long hair like structures that beat rhythimically to move mucus and trapped particles.
68
How do eyelids and blinking prevent infection?
- Protect the eye from dust and pathogens.
- Blinking spread tears and clears debris.
69
How does urine flow prevent infection?
Flushes out microorganisms from the urinary tract.
70
How does saliva flow prevent infection?
Washes microbes and food from mouth.
71
How do hairs from the nose and ears prevent infection?
Trap majority of dust and particles preventing entry into body.
72
What are the different types of chemical barriers?
- Lysozyme
- Stomach Acid
- Vaginal Secretions
- Sweat and Sebum
- Urine (Acidity_
73
How do lysozymes prevent infection?
- Is an enzyme that kills bacteria by breaking down the cell wall.
- Found in tears, saliva, sweat and tissue fluid.
74
How does stomach acid prevent infection?
Strong hydrochloric acid (HCL) kills bacteria ingested with food or trapped in mucus.
75
How do vaginal secretions prevent infection?
Naturally acidic to inhibit bacterial growth.
76
How does sweat and sebum prevent infection?
- Sweat contains salt and fatty acids creating a hostile environment for microbes.
- Sebum contains antibacterial compounds.
77
How does urine acidity prevent infection?
It is slightly acidic and flushes out bacteria.
78
What is an example of a microbiological barrier?
Normal flora (Microbiota)
79
How does normal flora prevent infection?
- Non-pathogenic bacteria live on the skin, gut, mouth and genital tract.
- Take up space and nutrients that pathogens would need to survive.
- Produces substances (fatty acids) that inhibit growth of harmful microbes.
80
What are the 4 protectice reflexes?
1) Sneezing
2) Coughing
3) Vomiting
4) Diarrhea
81
How does sneezing prevent infection?
- Stimulus: Irritation in the nasal cavity.
- Mechanism: Rapid expulsion of air through nose and mouth.
- Removes mucus, microbes and irritants from respiratory tract.
82
How does coughing prevent infection?
- Stimulus: Irritation in lower respiratory tract (bronchi)
- Mechanism: Forceful ejection of air from lungs.
- Clears mucus and pathogens from airways.
83
How does vomiting prevent infection?
- Stimulus: Psychological triggers or stomach stretching.
- Mechanism: Contraction of diaphragm and abdominal muscles.
- Expels contents from stomach removing ingested pathogens.
84
How does diarrhea prevent infection?
- Stimulus: Irritation in the intestines by bacteria or viruses.
- Mechanism: Increased peristalsis.
- Prevents absorption of pathogens and quickly eliminates them.
85
What is the innate immune response?
It is the body's first line and non-specific line of defence against all pathogens.
86
What is phagocytosis?
Is the process by which phagocytes (specialised white blood cells) engulf, digest and destroy foreign particles.
87
What is the role of phagocytes?
Phagocytes such as neutrophils, macrophages and dendritic cells are essential in identifying and removing pathogens through phagocytosis. They are also known as Antigen Presenting Cells (APCs) in the adaptive immune response by presenting antigens to T and B cells.
88
What are the 4 steps of phagocytosis?
1) Phagocyte detects and moves towards pathogen using chemical signals.
2) Phagocyte engulfs pathogen into a vesicla (phagosome)
3) Lysosomes fuse with the phagosome and release enzymes to digest to pathogen.
4) Harmless debris is expelled from the phagocyte.
89
What is inflammation?
Is a localised non-specific response to tissue damage or infection.
90
What are the 5 symptoms of inflammation?
1) Redness
2) Heat
3) Swealling
4) Pain
5) Loss of Function
91
What are the steps of inflammation?
1) Tissue damage acitvates mast cells which release histamine and heparin.
2) Histamine allows vasodilation which increased blood flow and permeability.
3) Heparin prevents clotting which allows blood to continues to flow to the damaged tissue.
4) However, a clot still forms to localise infection.
5) Cytokines attract phagocytes (especially neutrophils)
6) Phagocytes engulf microbes which die then a pus forms.
7) Repair begins and cells go through mitosis and replace damaged cells.
92
How does a fever occur?
1) Pyrogens act on the hypothalamus which sets a higher 'normal' body temperature due to infection.
2) The person feels cold due to thermoreceptors causing vasoconstriction and shivering.
3) The body temperature then rises to meed increased body temperature.
4) The fever then breaks and normal body temperature is re-established.
5) The person now feels hot and skin is red throug vasodilation and person begins sweating due to high temperature.
93
What are benefits of fevers?
- Slows growth of some pathogens.
- Speeds up healing throug enzyme action.
94
What are dangers of fevers?
- High fever may cause death.
- Can cause convulsions and brain damage.
95
What are specific defences (adaptive immunity)?
They are targeted immune responses against particular pathogens.
96
What is an immune response?
Is the body's reaction to the detection of a non-self antigen.
97
Where are B cells produced and mature?
Produced and mature in the bone marrow.
98
Where are T cells produced and mature?
They are produced in the bone marrow and mature in the thymus.
99
What is antibody-mediated immunity (humoural response)?
- Provides resistance before microorganism enters cell.
- Produces antigen specific antibodies to fight extracellular pathogens.
100
What is cell-mediated immunity?
- Provides resistance once foreign particles enter the cell.
- Does not produce antigen specific antibodies to fight intracellular pathogens.
101
What are the steps of antibody-mediated immunity?
1) Antigen enters the body and is detected by APCs.
2) APC presents the antigen to a specific B-cell.
3) T-helper cells bind and release cytokines.
4) Cytokines activate B-cell.
5) The B-cell enlarges and undergoes mitosis to form clones.
6) Clones then differentiate into:
- Plasma cells: Secrete antibodies into blood/lymph which binds to the antigen-antibody complex.
- Memory B-Cells: Stay in tissue which are able to recognise the original antigen and reproduce much faster.
102
What is a primary response?
The initial immune response to a pathogen:
- Slow and weak
- Takes time for B-cells to differentiate and produce antibodies.
103
What is a secondary response?
Occurs after re-exposure to the same antigen:
- Faster and stronger due to memory cells.
- Antibody levels rise rapidly and last longer.
104
How do antibodies work to protect the body?
1) Neutralisation: Bind to toxins/enzymes to block function.
2) Prevent Virus Entry: Bind to viral surfaces.
3) Opsonisation: Coat pathogens to enhance phagocytosis.
4) Agglutination: Clump pathogens together.
5) Precipitation: Make soluble antigens insoluble phagocytosis.
105
What are the steps of cell-mediated immunity?
1) An APC (macrophage or dendritic cell) engulfs the pathogen.
2) The pathogen is broken down as lysosymes fuse with the vesicle called a phagosome and antigen fragments are displayed on the surface.
3) A specific T-cell encounters the presented antigen and becomes sensitised.
4) This cell enlarges and divides to form clones through mitosis.
5) The clones differentiate into different T-cells.
- Killer T Cells
- Helper T-Cells
- Suppressor Cells
- Memory T-Cells
106
What are killer t-cells?
Seek out and destroy infected or abnormal body cells by releasing perforin.
107
What are helper t-cells?
Release cytokines which:
- Attract macrophages and more lymphocytes.
- Cause lymphocytes to become more sensitised.
- Stimulate phagocytosis.
- Enhance killer t-cell activity.
108
What are suppressor t-cells?
Regulate and slow the immune response once the threat is eliminated.
109
What are memory T-cells?
Remain in tissues to rapidly respond to future infections.
110
What is active immunity?
When the body produces its own antibodies in response to exposure to an antigen.
111
What is natural active immunity?
Body makes own B-cells and T-cells and antibodies after infection.
112
What is artificial active immunity?
Antigens introduces through vaccination and produces memory cells.
113
What is passive immunity?
When a person receives antibodies produces by another organism.
114
What is natural passive immunity?
Antibodies from mother to baby through breast feeding.
115
What is artificial passive immunity?
Antibodies injected through a serum to provide immediate short-term protection (tetanus injection).
116
What is a vaccination?
The aritifical introduction of antigens into the body to stimulate a immune response such as the production of antibodies and memory cells without causing a disease.
117
What is immunisation?
The process of developing immunity either naturally (infection) or artificially (vaccination)
118
What are the 4 types of vaccines?
1) Live attenuated
2) Inactivated
3) Toxoid
4) Sub-unit
119
What are live attenuated vaccines?
Contains weakened versions of pathogens that still stimulate immunity.
120
What are inactivated attenuated vaccines?
Contains killed pathogens that cannot replicate but still trigger immunity.
121
What are toxoid vaccines?
Contains inactivated toxins produced by bacteria.
122
What are sub-unit vaccines?
Contains fragments of pathogen, such as protein antigens.
123
Why don't vaccinations start until a child is 2 months old?
- A newborn baby has maternal antibodies passed via the placenta and breast milk.
- These antibodies neutralise vaccine antigens before the baby's immune system can respond.
- The baby's immune system needs time to mature.
124
What is the role of booster vaccines?
- Stimulate a stronger secondary immune response.
- They help produce more memory cells and maintain a high-level of antibodies for long-lasting immunity.
- Boosters are given after initial antibodies decline so needs to be given at a specific time.
125
What are health issues considered with vaccination?
- Safety of vaccines (side effects and allergies).
- Ensuring vulnerable groups (elderly, infants) are protected.
126
What is herd immunity?
Is achieved when a large portion of the population is immune reducing the spread of disease and protecting those who cannot be vaccinated.
127
What are social issues considered with vaccination?
- Misinformation, fear or lack of trust in science.
- Religious or personal beliefs influencing vaccine refusal.
128
What are cultural issues considered with vaccination?
- Language barriers or cultural beliefs affecting acceptance.
- Need for culturally sensitive education and outreach.
129
What are economic issues considered with vaccination?
- Cost of vaccines and distributions.
- Funding for vaccination programs, especially in low-income areas.
- Equity in access (rural vs urban).
