Unit 4 - Response to infection Flashcards
Communicable disease
when a disease is passed from one infected person to another
contagious
passed from human to human
vectors
passed to humans via animals such as mosquitoes
Bacteria Characteristics
- No nucleus. DNA floats freely
- slime layer around the outside
- cell membrane
- cell wall provides structural support & protection
- flagella for movement in some bacterias
· Unicellular and microscopic
· Shape determines their classification
Have plasma membrane, ribosomes, single circular strand of DNA (chromosome), and plasmids (small circular pieces of DNA)
Pathogen
disease causing organisms
transmission of pathogens through contact
- Physical contact
- Direct touching the infected person
- Indirect touch an object that an infected person has touched
Eg. Skin infections + STI’s
transmission of pathogens through bodily fluids
- Blood or other bodily fluids (infected person) transported to mucous membrane or bloodstream (uninfected person)
- Mucous membranes: nose, mouth, throat, genitals
- Enter through a needle or broken skin (pathogens enter)
Eg. HIV, Hepatitis B
transmission of pathogens through droplets
- Drops are emitted containing pathogens
- Breaking, talking, sneezing
Eg. Measles, mumps, cold, flu
transmission of pathogens through vectors
- Transfer of pathogens by other animals (mites, ticks, insects)
- Can be indirect àhouse flies contaminating food
Spread by a specific vector/vector born disease àmalaria & dengue by mosquitoes
non-specific defences
works on all pathogens
specific defences
directed at a particular pathogen
External Defence Mechanisms Against Pathogens
· Digestive tract: contains acids + enzymes that can destroy pathogens before they cause infection
· Urogenital tract: contains mucous membranes and other defence mechanisms that prevent pathogens from entering the body
· Respiratory system: includes nose, throat and lungs, lined with mucous membranes and cilia that trap and remove pathogens
· Ear: ear canal contains wax and other substances that prevent pathogens from entering body
Eye: eye is protected by tears, contain enzymes that can destroy pathogens
Non-Specific Defences Against Disease - skin, mucus, hairs, cilia
· Skin:
o acts as physical barrier
o prevents pathogens from entering body
o Bacteria occupies area and pathogens find it difficult to enter
o Sebum: oily secretion by oil glands in skin that contain substances that kill some pathogens
o Sweat: secreted onto skin and contains salts and fatty acids that prevent the growth of many micro-organisms
· Mucus:
o Mucous membranes line body cavities to open to the exterior
o Secrete mucus which traps particles and stops entry of micro-organisms
o Digestive, urinary and reproductive are all protected this way
· Hairs:
o Found in nasal cavity, ears and nose
o Hairs + layer of mucus trap 90% of particles when inhaled
· Cilia:
o Tiny-hair like projections from cells
o Are on the mucous membranes lining the nasal cavity, trachea and other air passages
Cilia moves mucus (containing particles) to throat where it is coughed up or swallowed
non-specific defences against disease - acids, lysozyme, cerumen, movement of fluid
· Acids:
o Kills many of the bacteria taken in with food or in mucus swallowed.
o Stomach juices
o Vaginas have acid secretion
o Urine
o Sweat
· Lysozyme:
o Enzyme that kills bacteria
o Found in saliva, sweat, secretions of nose, tissue fluid, and tears
· Cerumen:
o Called ear wax
o Protects outer ear against infection
o Acidic and contains lysozymes
· Movement of fluid
o Flushing action of body fluids helps keeps some area free of pathogens
o Urine - flowing through urethra, prevents bacterial growth, helps to stop bacteria reaching bladder and kidneys
o Also includes tears, sweat and saliva
Protective Defences/Reflexes
Automatic involuntary response to a stimulus
· Sneezing:
o Stimulus = irritation of walls of nasal cavity
· Coughing:
o Stimulus = irritation in the lower respiratory tract (bronchi + bronchioles)
· Vomiting:
o Stimuli = psychological
o Excessive stretching of stomach and bacterial toxins can all induce vomiting
· Diarrhoea:
Stimuli = irritation of the small and large intestines by bacteria, viruses or protozoans
Internal Non-Specific Defences: Phagocytosis
· This process by which certain immune cells engulf and destroy pathogens or other foreign substances in the body
· This process can be broken down into 6 stages
1. Phagocyte moves to the bacterium
2. Phagocyte changes shape to completely enclose bacterium
3. Lysosomes in phagocyte contains destructive enzymes
4. enzymes are released and destroy bacterium
Harmless particles are released from phagocyte
Neutrophils
first cells to arrive at the site of infection and are the most abundant immune cells involved with phagocytosis. Short-lived cells that can engulf and destroy bacteria, but are not as effective against larger pathogens
Macrophages
long-lived cells that can engulf and destroy a variety of pathogens, as well as dead cells and debris. They are also involved in presenting pieces of the pathogens to other immune cells, which helps to activate the adaptive immune response
Dendritic cells
specialised cells that can engulf and present pieces of the pathogens to other immune cells, which helps to activate the adaptive immune response
Natural killer cells
cells that can recognise and destroy infected cells or cells that are displaying abnormal behaviour
Purpose of Inflammatory Response
o Reduce the spread of any pathogens, to destroy them and to prevent the entry of additional pathogens
o Remove damaged tissue and cell debris
o Begin repair of the damaged tissue
Four signs: redness, swelling, heat, and pain
Inflammatory Response 7-steps:
- Mechanical damage / local chemical change activate mast cells which release histamine, heparin and other chemicals to the tissue fluid
- Histamine increase blood flow via vasodilation making capillary walls more permeable causing heat, redness & swelling
- Heparin prevents clotting and slow down spread of pathogen
- Complement proteins released by the mast cells attract phagocytes, like neutrophils which actively consume microorganisms
- Inflammation in the tissue stimulates the pain receptors.
- Phagocytes eventually die, forming pus
- New cells are produces by miosis for tissue repair
Fever
- Elevation in blood temperature
- Caused by the hypo, resetting to a higher level than usual in response to pyrogens (interleukin-1, released by WBC during inflammatory response)
Increase heat production = vasoconstriction & sweating occurs
Lymphatic System
Network of lymph capillaries joined by a larger lymph vessel
Lymphatic System Function
o Collect fluid escaping from blood capillaries back to the circulatory system
o Large particles get trapped in the meshwork of the fibres, which then gets engulfed by the microphages,
o When infections occur, formation of lymphocytes increase and lymph nodes become swollen and sore
Immunity
esistance to infection by invading micro-organisms, and the presence of memory cells allows the body to respond quickly enough to deal with any invasion by pathogenic micro-organisms before symptoms of disease occur
- Ability to respond is either natural (no human interaction) or artificial (giving people antibody)
Immune Response
· Immune response: homeostatic mechanism, helps deal with the invasion of micro-organisms or foreign substances and restore internal environment to its normal condition
· Main cells involved are B-cells and T-cells (WBC called lymphocytes)
Similarities of B-T Cells
Produced in bone marrow
Involved in adaptive immune response (can recognise and respond to specific pathogens)
Have receptors on their surfaces (allow them to recognise antigens)
B-cells
Maturation: in bone marrow
Purpose: produce antibodies
Production: produce antibodies (proteins that bind to antigens and mark pathogens for destruction)
Recognition: can recognise and bind to antigens that are freely circulating the body’s fluids e.g., blood & lymph
Types: One type
Memory cells: produce memory cells to quickly respond to future infections by the same pathogen providing long-term immunity
T-cells
maturation: in thymus gland
purpose: directly attack infected cells
production: DONT produce antibodies (but directly attack and destroy infected cells)
recognition: can only recognise antigens displayed on surface of cells
types: multiple types eg. helper, cytotoxic
Memory cells: produce memory cells and becomes activated more rapidly when exposed to same pathogen
Passive:
o refers to when a person receives antibodies produced by someone else, meaning that the individual’s body plays no part in the production of antibodies
o short-lived, only lasts until antibodies are broken down and excreted
o naturally -> mother pass antibodies across placenta to developing foetus
artificial -> person is injected with antibodies to combat a particular infection
active
o results when the body is exposed to a foreign antigen and manufactures antibodies in response to that antigen
o last longer (due to memory cells)
o naturally -> getting a disease and recovering
artificially-> etting vaccinated against a disease
Self-antigen
produced in a person’s body do not cause an immune response
Non-self-antigen
any molecule that is not normally present in the body’s own tissues, and that can trigger an immune response
recognition:
when a non-self-antigen is recognised by the immune system, it triggers an immune response that involves the activation and proliferation of immune cells (B-cells and T-cells), that can specifically recognise and target that antigen
this immune response is essential for protecting the body against harmful invaders, helps to eliminate the pathogen or abnormal cells that bear the non-self-antigen
Anti-Body Mediated Response/Immunity (Humoral)
- Refers to the production and release of antibodies
- Occurs before pathogen enters cell
1. Antigen-presenting cells recognise, engulf and digest pathogens, displaying the antigen on their surface.
2. Antigen-presenting cell reach the lymphoid tissue and present the antigen to lymphocytes (B-cells & T-cells)
3. Helper T-cells are stimulated by antigen-resenting cells = clone themselves and release cytokines
4. B-cells are stimulated / activated, enlarge and divide to produce clones (undergo rapid cell division)
a. Some cells are now called plasma cells
b. Some cells are ‘memory B-cells’
5. Plasma cells secrete AB that reach site of invasion and combine with AG
6. AB combines to form AB-AG complex
Action of AB
· Agglutination/clumping together of pathogen
· Make more easily consumed by phagocytosis/enhance phagocytosis
· Neutralisation of toxins
· Coat bacteria = easily consumed by phagocytes
· Dissolve bacteria
· Make membranes more permeable
· Make soluble substances insoluble
Cell Mediated Immunity
Refers to the production and release of three different kinds of cells
Occurs inside cell (intracellular) through phagocytosis
1. Antigen-presenting cells recognise, engulf and digest pathogens, displaying the antigen on the surface.
2. AG reaches the lymphoid tissue and is presented to a specific T-cell (different AG have a specific T-cell) by a macrophage or B-cell
3. T-cell is sensitised and divides into clones through mitosis
4. Most cells of the clone are memory cells
5. Rest of the cells further develop into T-cells with specialised function:
a. Killer T-cells: destroy the invading AG by attaching to the AG and secreting substance that bill it
b. Helper T-cells: secrete substances that further sensitive T-cells, attract macrophages to point of infection and increase phagocytic activity
c. Suppressor T-cells: secrete substances that inhibit the action of the T-cells once infection has been dealt with
immunisation
programming the immune system so that the body can respond rapidly to infecting micro-organisms
Vaccination
the introduction of antigens to a person so that they acquire immunity without suffering from the illness
Vaccine
an antigen preparation used in artificial immunisation
live attenuated vaccines:
○ reduced virulence (reduced ability to produce disease symptoms)
○ therefore, immunised person does not contract disease but manufactures antibodies against the antigen
Eg. Polio, tuberculosis
inactivated vaccines:
○ contain dead micro-organisms
○ produce an immunity that is shorter lasting than immunisation
Eg. Cholera, typhoid, whooping cough
toxoid vaccines:
○ toxins produce by that bacteria can be inactivated, so when they are injected, they do not make the person ill
○ toxoids: inactivated toxins
Eg. Diphtheria, tetanus
sub-unit vaccine:
○ instead of using a whole dead or attenuated micro-organism, a fragment of the organism can be used to provoke the immune response
Eg. Human papilloma virus, hepatitis B
Antibiotics
drugs that are used to fight infections of micro-organisms, particularly bacteria
* Cannot be used to treat viral infections
* Each antibiotic is effective for only certain types of bacterial infection
* First antibiotic identified was penicillin (works by preventing the synthesis of the walls of the bacterial cells, inhibiting the reproduction of bacteria
* Two types of antibiotics:
Two types of antibiotics:
○ Bactericidal àkill bacteria by changing structure of cell wall or cell membrane, or by distributing the action of essential enzymes
Bacteriostatic àstop bacteria reproducing, usually by disrupting protein synthesis
Broad-spectrum antibiotics
an antibiotic that affects many types of bacteria
Narrow-spectrum antibiotics
an antibiotic that affects only a particular type of bacteria
Multiple drug resistance
resistance of some strains of bacteria to most of the available antibiotics
Total drug resistance
resistance of some strains of bacteria to all antibiotics
Antiviral drugs
drugs used specifically for treating viral infections
Antibiotics
Definition: drugs that are used to fight micro-organisms, particularly bacteria
Target: Target and kill bacteria
Spectrum of activity: Narrow or broad spectrum
Mechanism of Action: Disrupting the bacteria cell wall, protein synthesis or DNA replication
Resistance: Resistance is a significant problem due to overuse or misuse
Treatment duration: Short, last 7-14 days
Examples: Penicillin, amoxicillin
Antivirals
Definition: used specifically for treating viral infections
Target: & inhibit replication of viruses
Spectrum: more specific
Mechanism: Targeting viral enzymes, inhibiting viral entry into host cells, or blocking viral nucleic acid replication
Resistance: Resistance can occur but less common and less severe
Treatment of Duration: Resistance can occur but less common and less severe
Examples: Amantadine
Similarities of Antivirals and Antibiotics
Drugs used to treat infectious diseases caused by micro-organisms
Have potential side effects (Eg. Nausea, diarrhea, allergic reactions
Require prescription from healthcare provided, only be used as directed
Can interact with other medications
Factors affecting vaccinations
- Health issues:
○ Allergic reactions - Social factors:
○ Ethical concerns with testing on animals -> some people don’t believe animals should be used to test for vaccines, against animal cruelty
○ Ethical concerns with use of human tissue to produce vaccines
○ Concerns about promoting sexual activity in teens - Cultural factors:
○ Religious beliefs-> religious beliefs stop parents immunising children - Economic factors:
Cost of vaccine
