Module 4.1.1 - Communicable diseases Flashcards
What is a disease?
Condition that impairs normal function if an organism
What is a pathogen?
Microorganism that causes disease
What is a communicable disease?
Disease spread from person to person
What are communicable diseases caused by?
Pathogen
What does tuberculosis affect and caused by?
Animals/human/cattle
- bacterium
What does bacterial meningitis affect and caused by?
Humans
- bacterium
What does ring rot affect and caused by?
Potatoes/tomatoes
- bacterium
What does AIDS/HIV affect and caused by?
Humans
- virus
What does tobacco mosaic virus affect and caused by?
Plants
- virus
What does influenza affect and caused by?
Animals/humans
- virus
What does black sigatoka affect and caused by?
Banana plants
- fungus
What does ringworm affect and caused by?
Cattle
- fungus
What does athlete’s foot affect and caused by?
Humans
- fungus
What does potato/tomato blight affect and caused by?
Potatoes/tomatoes
- Protoctista
What does malaria affect and caused by?
Animals/humans
- Protoctista
What is direct transmission of disease?
Transmitted directly from one organism to another
- can be transmitted through droplet infection, sexual intercourse and touching infected organism
What are examples of direct transmitted diseases?
- HIV transmitted between humans or from mother to unborn child via placenta
- athlete’s foot via touch
What is indirect transmission of disease?
Transmitted from one organism to another via an intermediate
- can be transmitted through air, water, food, vector
What are examples of indirect transmitted diseases?
- potato/tomato late blight, spores carried between plants, in air then water
- malaria spread between humans via mosquitos (vectors), carry it and spread it
What factors affect transmission of diseases?
Living conditions - overcrowded will have more chance of spread
Social factors - income/occupation/area?
Climate - wind/water/heat can affect the spread
What are the 6 animal defences?
- skin
- mucous membranes
- blood clotting
- inflammation
- wound repair
- expulsive reflexes
What do pathogens need to cause disease?
Need to enter an organism
What is the mucous membrane defence?
Protects body openings exposed to environment, some membranes secrete mucous
What is the animal skin defence?
Physical and chemical barrier, blocks pathogens from entering, produces chemicals that are antimicrobial, can lower pH which inhibits growth of pathogens
What is the animal blood clotting defence?
Mesh of protein fibers, plug wounds to prevent pathogen entry and blood loss, formed by chemical reactions in body that take place when platelets are exposed to damaged blood vessels
What is the animal inflammation defence?
Signs include swelling, pain, heat and redness, can be triggered by tissue damage, causes swelling and helps isolate any pathogens that may have entered damaged tissue, molecules cause vasodilation which increases flow to affected area, makes area hot and bring white blood cells to area to fight off any pathogens
What is the animal wound-repair defence?
Skin is able to repair itself in event of injury and reform barrier against pathogen entry, surface is repaired by outer layer of skin cells dividing and migrating to edges of wound, tissue below wound contracts to bring edge of wound closer together, repaired using collagen fibers - too many collagen fibers form a scar
What is the animal expulsive reflexes defence?
Includes coughing and sneezing, sneeze happens when mucous membranes in nostrils are irritated by dust/dirt, cough stems from irritation in respiratory tract, both an attempt to exert foreign objects/pathogens, happen automatically
What are the 3 plant defences?
- physical
- barrier
- chemical
What is a physical plant defence?
Most have waxy cuticle which protects against pathogen entry, also stops water collecting on leaf, reduces risk of infection by pathogens that’re transferred between plants in water, cell walls forms a barrier against pathogens that make it past waxy cuticle, plants produce polysaccharide called glucose, callose gets deposited between plant cell walls and plasma membranes during times of stress
What is a barrier plant defence?
Callose deposition may make it harder for pathogens to enter cell, at plasmodesmata may limit spread of viruses between cells
What is a chemical plant defence?
Plants produce antimicrobial chemical which kills pathogens or inhibits their growth, other chemicals secreted are toxic, reduces amount of insect feeding on plants, reduces risk of infection by plant viruses caused by insect vectors
What is the immune system?
Body’s reaction to foreign antigens
When does the immune system respond?
If pathogens gets past primary defense
What are antigens?
Molecules found on surface of cells
What activates the immune response?
Pathogens entering the body, antigens on cell surface are identified
What is a non-specific response?
Happens in same way for all microorganisms, whatever foreign antigens they have
What is a specific response?
Aimed at specific pathogens, involves white blood cells called T and B lymphocytes
What are the main stages of the immune system?
- phagocytosis
- T lymphocyte activation
- B lymphocyte activation and plasma cell production
- antibody production
What is the phagocytosis stage?
- recognises antigens of pathogen
- cytoplasm of phagocyte moves around pathogen, engulfing it
- opsonin’s make it easier
- pathogen now contained in phagosome in cytoplasm of phagocyte
- lysosome fuses with phagosome, enzymes breakdown pathogen
- phagocyte presents pathogen’s antigens, sticks antigens on its surface to activate other immune system cells, acting as antigen presenting cells (APC)
What is a phagocyte?
- white blood cell that carries out phagocytosis
- found in blood and tissue
- carry out non specific immune response
What are neutrophils?
Type of phagocyte
- first white blood cell to respond to pathogen inside body
- move towards wound in response to signals from cytokinesis
- cytokines are released by cells at site of wound
What is T lymphocyte activation?
Another type of white blood cell
- receptors bind to antigens presented by APC’s
- each T cell has a different receptor on surface, receptor meets complimentary antigen and binds to it
- process activates T lymphocytes and called clonal selection
- activated T lymphocytes undergo clonal expansion
- different activated T lymphocytes carry out different functions
What functions do different T lymphocytes carry out?
T helper cells - release substances to activate B lymphocytes and T killer cells
T killer cells - attach and kill cells infected with virus
T regulatory cells - suppress immune system cells from mistakenly attacking host’s body cells
- some become memory cells
What is B lymphocyte activation and plasma cell production?
- type of white blood cell
- covered with antibodies
- each B lymphocyte has different shaped antibody on it membrane, so different ones bind to different shaped antigens
- when antibodies on surface of B lymphocytes meet complementary antigen, binds to it
- together with substances released from helper T cells, activates B lymphocytes
- another example of clonal selection
- activated B lymphocytes divides, by mitosis, into plasma cells and memory cells
What is antibody production?
- plasma cells are clones of B lymphocytes
- secrete lots of antibodies, specific to antigen, into blood
- antibodies bind to antigens on surface of pathogen to form lots of antigen-antibody complexes
- is signal for immune system to attach and destroy pathogen
What is cell signaling and immune response?
How cells communicate
- cell may release substance that binds to receptors on another cell, causes response of other cells
- important to immune response, helps activate different types of blood cells that are needed
What are blood smears?
- smear of blood on microscope slide
- stains added to differentiate cells
What are antibodies?
- blood protein produced in response to and counteracting specific antigen
- combine chemically with substances which body recognises as alien
What is the structure of antibodies?
- glycoprotein
- made up of 4 polypeptide chains (2 heavy, 2 light)
- each chain has variable region and a constant region
What is a variable region in an antibody?
- forms antigen-binding sites
- shape of them is complimentary to particular antigen
- differs between antibodies
What is a hinge region in an antibody?
Allows flexibility when binding
How do antibodies agglutinate pathogens?
- each antibody has 2 binding sites to bind at same time, become crumpled together
- phagocytes then bind to antibodies and phagocytose a lot of pathogens all at once
- antibodies behaving in this way are called agglutinins
What is the disulphide bridge in an antibody?
Type of bond that holds polypeptide chains of protein together
What is a constant region in an antibody?
- allows binding to receptors on immune system cells
- is same in all antibodies
What are the 3 roles of antibodies in clearing infections?
- agglutinating pathogens
- neutralising toxins
- preventing pathogens binding to human cells
How do antibodies neutralise toxins?
- toxins have different shapes
- antibodies called anti-toxins can bind to toxins produced by pathogens
- prevents toxins from affecting human cells, toxins are neutralised/inactivated
- toxin-antibody complexes are also phagocytosed
How do antibodies prevent pathogens binding to human cells?
- when antibodies bind to antigens on pathogens, may block cell-surface receptors that pathogens need to bind to host cell
- means pathogens cant attach to or infect host cells
What is the primary immune response?
- when pathogen enters body for first time, antigens on surface activates immune system
- slow as aren’t many B lymphocytes that can make antibody needed to bind to pathogen
- body will produce enough of right antibody to overcome infection
- infected person will show symptoms of disease
What happens in the primary response?
- after being exposed to antigen, T and b lymphocytes produce memory cells
- memory cells remain in body for a long time
- memory T lymphocytes remember specific antigen and will recognise 2nd time around
- memory B lymphocytes record specific antibodies needed to bind to antigen
- person is now immune as body can respond quickly to 2nd infection
What is the secondary immune response?
- if same pathogen enters body again, immune system will produce quicker and stronger immune response
- clonal selection happens faster
- memory B lymphocytes divide into plasma cells that produce the right antibody to antigen
- memory T lymphocytes are activated and divide into correct type of T lymphocytes to kill cell carrying antigen
- secondary response often gets rid of pathogen before symptoms start to show
How do you maintain immunity?
- memory B and T lymphocytes only have limited lifespan
- someone immune to particular pathogen wont always stay immune
- once all have died, person may become susceptible to attack to pathogen again
- immunity can be maintained by being continuously exposed to pathogen so can continue to make more B and T lymphocytes
What are the 2 types of immunity?
- passive
- active
What is active immunity?
Your immune system makes its own antibodies after being stimulated by an antigen
- can be natural or artificial
What is natural and artificial active immunity?
natural - become immune after catching a disease
artificial - become immune after being given a vaccination containing a harmless dose of antigen
What is passive immunity?
Get from being given antibodies made by different organism (immune system doesn’t produce its own)
- can be natural or artificial
What is natural and artificial passive immunity?
natural - baby becomes immune to antibodies it receives from its mother, through placenta and in breast milk
artificial - become immune after being injected with antibodies from someone else
What is autoimmune disease?
- sometimes an organisms immune system isn’t able to recognize self-antigens
- immune system treats the self-antigens as foreign and launches response against the organisms own tissues
- disease resulting from this abnormal immune response is known as autoimmune disease
What are vaccinations?
- contains substances that causes your body to produce memory cells against a particular pathogen, without pathogen causing disease
- means you become immune without getting any symptoms
- substances in vaccines may be antigens, which could be free or attached to a dead or weakened pathogen
- substances can also be other molecules, such as mRNA designed to code for antigens found on a pathogen
- when mRNA enters body cells, provides instructions needed for cells to produce these antigens, triggers memory cells to be made
What are examples of autoimmune diseases?
Lupus - immune system attacking cells in connective tissues, damages tissue and causes painful inflammation can affect skin, joints and organs
Rheumatoid arthritis - immune system attacking cells in joints, causes pain and inflammation
What are disadvantages of vaccinations orally?
- could be broken down by enzymes in stomach of molecules of vaccine may be too large to be absorbed into blood
- sometimes booster vaccines are given later on to make sure more memory cells are produced
How can vaccines be taken?
- orally
- injected
What is herd immunity?
Epidemics (mass outbreak of disease) can be prevented if large % of pop is vaccinated
- even if people who haven’t been vaccinated are unlikely to get disease, because there’s no one to catch is from
What are antibiotics?
- chemicals that kill or inhibit growth of bacteria
- used by humans as drugs to treat bacterial infection
- useful as can usually target bacterial cells without damaging human body cells
What is the Influenza vaccine?
- changes every year
- antigens in surface of virus change regularly forming new strains of virus
- strains are immunologically distinct
What was the first antibiotic to be discovered?
Penicillin
What are routine vaccines?
MMR - protects against measles, mumps and rubella, usually given to children as injection around 1 year old and before starting school, contains attenuated measles, mumps and rubella viruses
Meningitis C - protects against bacteria that can cause meningitis C, first given as injection to babies at 3 months old, boosters given to 1 year old and teenagers
What risks to antibiotics have?
- can cause side effects
- severe allergic reactions in some people
- biggest is antibiotic resistance
What is Penicillin?
- 1st antibiotic discovered
- became widespread mid 20th century due to successful treatment of soldiers in WW2
- death rate from infectious bacterial disease has fallen dramatically
What is antibiotic resistance?
- genetic variation in pop of bacteria
- genetic mutations make some bacteria naturally resistant to an antibiotic
- for bacterium, antibiotic resistance is a big advantage
What has happened due to the increase in use of antibiotics?
- Increased antibiotic resistance, becoming more common
- less able to treat some life threatening bacterial infections
What are examples of antibiotic resistant bacteria?
MRSA - causes serious wound infections, resistant to several antibiotics
Clostridium difficile - infects digestive system, usually causing problems in people who have already been treated with antibiotics, harmless bacteria are killed by the antibiotics which C.Difficile is resistant to, allows it to flourish + produce a toxin which causes severe diarrhea, fever + cramps
How can antibiotic resistance be prevented?
- developing and modifying existing/new antibiotics
- doctors encouraged to reduce use of antibiotics, not prescribe for minor infections or to prevent them
- patients advised to take all prescribed antibiotics to make sure infection is fully cleared/ all bacteria killed
What are many medical drugs manufactured from?
Natural compounds found in plants, animals or microorganisms
- need to be protected by maintaining biodiversity
What is the future of medicine?
- your genes determine how your body responds to certain drugs
-different people respond to same drugs in different ways, certain drugs more effective than others - personalized medicines are tailored to an individuals DNA
- doctors can use your genetic info to predict how you’ll respond to different drugs and prescribe most effective
What is synthetic biology?
Using tech to design and make things like artificial proteins, cells and microorganisms
