Chapter 12 - Communicable Disease Flashcards
What is a pathogen
Disease causing microorganism
Different types of pathogens
Bacteria
Fungi
Virus
Protoctista
Vector definition
Living or non living factor that transmits a pathogen from one organism to another
Water, mosquito
How do viruses infect
They take over cell metabolism
Viral DNA gets into the host
Their genetic material is inserted into host DNA
Uses host cell to make more viruses
Viruses reproduce rapidly and evolve to adapt to their host
Bust out of cell to infect others
What are protoctistas
Eukaryotic organisms
Need a vector to transfer them to their hosts
2 ways bacteria can be classified
By their shape
By their cell walls (gram staining)
What are fungi
Eukaryotic organisms
Multicellular
Saprophytes - feed on dead + decaying matter , can be parasitic
How do protoctistas infect
Take over cells and break them open
Digest the cells contents and use it to reproduce
How do fungi infect
Digest living cells and destroy them
How do bacteria infect
Produce toxins that damage the host cells by:
- breaking cell membranes
- damage enzymes
- interfere with hosts cells genetic material - can’t divide
Diseases caused by bacterium
Bacterial meningitis
Tuberculosis
Ring rot
Diseases caused by protoctistas
Potato / tomato late blight
Malaria
Diseases cause by fungi
Athletes foot
Ringworm
Black sigatoka
Tuberculosis affects
Animals - human and cattle
Damages and destroys lung tissue
Suppresses the immune system
Diseases caused by viruses
Tobacco mosaic virus
HIV AIDS
influenza
Bacterial meningitis affects
Humans (kids)
Cause blood poisoning
Rash
Ring rot affect
Potatoes and tomatoes
Gram positive bacteria
Damages leaves, tuber and fruit
HIV affects
Humans
Targets t-helper cells in immune system
Destroys immune system
Transcripts RNA to single strand of DNA
interacts with genetic material
Influenza
Animals
Kills ciliated epithelial cells in gas exchange system
Airways open to infection
Tobacco mosaic virus
Plants
Damages leaves, flowers, fruit
Stunts growth
Black sigatoka
Banana plants
Attack’s and destroys leaves
Turn black
Ring worm
Cattle
Grey white crusty areas in skin
Itchy
Athletes foot
Humans
Grows on and digests warm moist skin
Causes cracking and scaling, itchy
Potato blight
Potatoes and tomatoes
Destroys leaves, tuber, fruits
Malaria
Humans animals
Female mosquitos
Plasmodium passed on to people
What is direct transmission
Pathogen is transferred directly from one individual to another
Example of direct transmission
- Direct contact
- Inoculation - through cuts, break in skin
- Ingestion
What is indirect transmission
Pathogen travels from one individual to another via an intermediate
Examples of indirect transmission
Air , water, food, another object
Fomites- inanimate objects (socks)
Vectors- mosquitos
Spores- in air and water
Soil contamination
How do living conditions affect disease transmission
Overcrowded conditions increase disease transmissions
TB - droplet infection (directly)
- remain in air (indirectly)
How does climate affect disease transmission
Increased rainfall and wind - promote spread
Damp warm conditions increase disease survival
Potato late blight - spores spread
Mosquitoes - warm - ideal for breeding
How social factors affect disease transmission
High when
Limited access to:
Healthcare
Education
Preventing communicable disease in plants
Plant crops with space in between Clear fields throughly when harvesting Rotate crops Control insect vectors Hygiene practices - sterilising
How do plants recognise an attack
Receptors in cell membranes respond to molecules from pathogens
Stimulates release of signalling molecules
These trigger cellular responses by switching on genes
Responses = producing defensive chemicals
What physical defences do plants have
-Waxy cuticle =
barrier, stop water collecting on leaf - reduce infection transferred
-Cell walls
-produce Polysaccharide called CALLOSE =
Deposited between cell wall and plasma membrane
- harder for pathogens to enter
- at plasmodesmata = limit spread of virus between cells
- blocks sieve plates in phloem
What chemical defences to plants have
Produce antimicrobial chemicals (antibiotics)
- kill invading pathogens, inhibit their growth - interfere with cell membranes
- saponins / phytoalexins
Secrete chemicals toxic to insects
- reduces plant viruses carried by insect vectors
- cyanide
How does skin prevent infection
blocks pathogens from entering body
produces antimicrobial chemicals - lower pH , inhibiting growth of pathogen
How does woUnd repair prevent infection
Skin can repair itself by reforming a barrier against pathogen entry
- surface is repaired by outer layer of skin cells dividing and migrating to the edges of wound
- tissue below contracts to bring edges closer together
- repaired using collagen fibres
How does expulsive reflexes prevent infection
Sneezing and coughing - expel foreign objects from the body (mucous membrane)
Vomiting and diarrhoea - expel contents of gut along with pathogens
How do fevers get rid of pathogens
Raise body temperature
Inhibits pathogen reproduction
Immune system works faster
How does Mucous membranes prevent infection
protect the body openings that are exposed to the environment
secretes mucus that traps pathogens
contains phagocytes
contains lysozymes that destroy bacterial + fungal cell walls
How does blood clotting prevent infection
blood clot is a mesh of protein fibres
take place when platelets are exposed to damaged blood vessels
plug wounds
prevent pathogen entry
stop blood loss
How does inflammation prevent infection
damaged tissue activates mast cells that release histamines and cytokines
histamines increases the permeability of the blood vessels - leak fluid into surroundings - cause swelling * isolate the pathogens that have entered the damaged tissue cause vasodiliation - increases the blood flow - makes the area hot
cytokines
- brings white blood cells to fight of pathogens
How is phagocytosis carried out
Neutrophils and macrophages
Phagocytes are attracted to chemicals produced by pathogen
Phagocytes recognise the pathogen as non self
Phagocytes engulf pathogen by surrounding it with cell surface membrane until it pinches off to form vesicles called / cytoplasm moves around pathogen = phagosome
Phagosome fuses with lysosome to form = phagolysosome
Enzymes from lysosome digest and destroy pathogens
What are the 2 types of white blood cells
Neutrophils - multi lobed nucleus
Macrophage
What is an antigen
Molecules found on the surface of cells that trigger immune response
How are antigen presenting cells formed
Macrophages
Macrophage digests everything but antigens
Combines the antigens from the pathogen surface membrane with glycoproteins in the cytoplasm called = Major Histocompatibility Complex = MHC
The MHC complex moves these antigens to the macrophages surface membrane to become = APC
What is an APC
A cell that presents foreign antigens complexed with MHCs on its own cell surface membrane
What does MHC stand for
Major Histocompatibilty complexes
What do the cytokines released by phagocytes do
Proteins that act as messenger molecules
Informing other phagocytes that the body is under attack
Stimulating other phagocytes to move to infected area
Why are opsonins useful chemicals in phagocytosis
Chemicals that bind to pathogens and tag them
So they’re more easily recognised by phagocytes
Allow phagocytes to get closer to pathogens
Examining blood smears
What will you see
Red blood cells
Platelets = fragments of cells involved in blood clotting
Neutrophils
Monocytes
Lymphocyte
Visible features of
Neutrophils
- Multi lobed nucleus
- Grainy cytoplasm
Visible features of
Lymphocytes
- smaller than neutrophil
- nucleus takes up most space
Visible features of
Monocytes
- Biggest white blood cell
- Kidney bean shaped nucleus
- No grainy cytoplasm
What is the structure of an antibody
Y shaped glycoprotein called immunoglobulin
Made of 2 identical long polypeptide chains = heavy chain
2 dental short polypeptide chains = light chain
Chains are held together by disulfide
Hinge region = allows flexibility when the antigen binds to the antibody
Binding site = variable site - gives specificity
Allows binding to receptors on immune system = constant region
How do antibodies prevent the pathogen binding to human cells
- pathogens can’t invade host cells when part of an antigen-antibody complex by blocking the cell surface receptors the pathogen needs to bind to the host
Outline action or opsonins
- antigen-antibody complex acts as an opsonise so complex is more easily recognised an engulfed by phagocytes
Outline actions of agglutinins
- anti bodies act as agglutinins - causing pathogens carrying antigen-antibody complexes to clump together - prevents from spreading - easier for phagocytes to engulf at same time
Outline actions of antitoxins
Antibodies called antitoxins
Bind to toxins produced by pathogens
Prevent toxins from affecting human cells
Toxins are neutralised
What is the function of antibodies
- acts as an opsonin
- are agglutinins
- can neutralise toxins
- prevent from binding to human cells
What is active immunity
Immunity you get when your own immune system makes its own antibodies after being stimulated by antigens
What are the 2 different types of active immunity
Natural
Artificial
What is a example of
Natural active immunity
You become immune after catching a disease
You produce your own antibodies
What is a example of
Artificial active immunity
When you become immune after being given a vaccination
A weakened or dead pathogen
What is passive immunity
Immunity you get from being given antibodies by a different organism
Example of
Natural passive immunity
A baby gaining antibodies from mothers breast milk, or placenta
Colostrum
Example of
Artificial passive immunity
Immune after being injected with someone else’s antibodies
If you have tetanus, you are injected with antibodies against the tetanus toxin, from blood donations
What are the differences between active and passive immunity
Active
- long term
- creates memory cells
- takes time for protection to develop
- requires exposure to antigen
Passive
- short term
- takes immediate effect
- doesn’t create memory cells
- does not need antigens
What is cell mediated immunity
T lymphocytes respond to cells of an organism that have been altered
How does cell mediation work
Non specific defence of phagocytosis = produces APC
The CD4 receptors on the T helper lymphocytes meets a complementary antigen on an APC and binds to it - This activated the T-helper cells in a process called CLONAL SELECTION
Then undergoes CLONAL EXPANSION the T helper cells release interleukins and divide by mitosis and differentiate into different types of T cells that carry out different functions
What 4 things can cloned T cells do
Develop into T memory cells
Develop into T killer cells
They can release interleukins to increase phagocytosis
They can release interleukins to stimulate the division of B lymphocytes Increases antibody production
Name the 4 different types of T lymphocytes
T killer
T memory
T helper
T regulatory
What donT helper cells do
Their CD4 receptors bind to antigens on APC
Release interleukins
Which stimulate B cells
Produce different T cells
Stimulates macrophages to INGEST pathogens with antigen - antibody complex
What do T killer cells do
Destroy the pathogen carrying antigens
By producing a chemical called = perforin
That kills the pathogen
By making holes in cell surface membrane
Freely permeable
What do T memory cells do
Part of immunological memory
Remembrer the specific antigens
So when met again
Will divide rapidly to produce specific T killer cells
To destroy pathogen
What do T regulator cells do
Suppress the immune system
From other white blood cells
Once pathogen has been eliminated
To prevent autoimmune response
Interleukins important
What is humoral immunity
Produces antibodies to respond to foreign antigens
How does humoral immunity occur
B lymphocytes are covered with antibodies
These antibodies join with the complementary antigens on the pathogen
The B cell engulfs and processes the antigen to become a B cell APC
T helper cells bind to the B APC = CLONAL SÉLECTION
(B cell with correct antigen is selected for cloning)
T cells produce interleukins that activate B Cells to divide by mitosis = CLONAL EXPANSION
Why do B cells differentiate into
Plasma cells
B Effector cells
B Memory cells
What do plasma cells do
Primary immune response
Produce antibodies to a particular antigen
Release them into circulation
Disable antigens
Act act opsonins, agglutinins, antitoxins
What do effector cells do
Divide to form plasma cell clones
What do B memory cells do
Secondary immune response
Provide immunological memory
Programmed to remember antigen
Enables body to respond quickly when pathogen reenters
Why is the primary response slow
Antigens on pathogen active immune system
Not enough B lymphocytes to produce right antibody
Eventually will produce enough antibody - show symptoms
After exposure to antigen T + B make memory cells
Why is the secondary response faster
Immune system produces stronger, faster response
B Memory divide into plasma cells = make antibodies
T Memory divide into T cells to destroy pathogen
Before symptoms show
What is an auto immune disease
Response when the immune system acts against its won cells and destroys healthy tissue
Recognises “self cells” as foreign
Rheumatoid arthritis
Joints
Feet, wrists
Cure = anti inflammatory , immunosuppressant, steroids
Lupus
Affects skin and joints
Can attack organs
Cure = immunosuppressant, anti inflammatory, steroids
What are the principles of vaccination
1) pathogen is made safe so no risk of infection
- dead, inactivated, altered, attenuated
2) small amounts of safe antigen injected into blood
3) primary immune response triggered
4) memory cells made
5) come into contact again - secondary response is quicker and stronger
What is herd immunity
When most people in a community are vaccinated the disease become rare
Even people without the vaccines are unlikely to get it
Reduces the risk of an epidemic
What are routine vaccines
MMR =
- measles , mumps , rubella
- children
Meningitis C vaccine =
- protects against bacteria that causes Meningitis C
- 3 months, 1 year, teenager
Reasons for changes in vaccines and vaccination programmes
Influenza
Antigens on influenza surface change regularly
Forming new strains of virus
Memory cells from virus against 1 strain will not impact new strains
New vaccines are made every year that are most effective against the recent circulating viruses
Why do possible sources of medicine need to be protected
Uses natural compounds
Plants, animals, microorganisms
Penicillin = fungus
Cancer drugs = soil bacteria
Alzheimer’s = daffodils
What are personalised medicines
Tailored to an individuals genes
Doctor can predict how you will respond to medicine, and prescribe you the most effective using your genetic material
What is synthetic biology
Uses technology to design artificial proteins, cells, microorganisms
Cancer
- destroy cancer cells while leaving body healthy
Benefits of using antibiotics
Kill or inhibit growth of bacteria
Doesn’t damage human cells = isolated
Disadvantages of antibiotics
Can cause severe allergic reactions
Can form antibiotic resistance
- mutations occur so they become naturally resistant, spread the advantageous gene
Prevent by not giving to small infections
Making sure the course of medicine is ended so all bacteria is killed off
MRSA
Causes serious wound infection
Resistant to meticillin
Clostridium difficile
Harmless bacteria in digestive system killed, expect Cdifficile
Produces cramps, fevers, diarrhoea
