mod 4.1 snaprevise Flashcards
when does disease occur
when pathogens enter the body and cause damage
what are primary defences
non specific defences that prevent pathogens entering the body (its always the same response)
examples of primary defences
skin, mucus and membranes, expulsive reflexes
state stuff about the primary defence: skin
made up of cells called keratinocytes
keratinisation- cells die by the time they reach the surface- they act as barriers.
a large number of harmless microbes called skin flora also live on the skin- prevents pathogenic microbes from colonising on the skin by competing with them for nutrients
state stuff about the primary defence: blood clotting and wound repair
- when the skin is damaged, the blood is open for pathogens to enter.
- this is prevented by a blood clot forming in the wound
- when this blood clot dries, it forms a temporary seal called a scab which allows for skin to repair.
- to cause blood clotting, platelets and damaged tissues release clotting factors which activate an enzyme cascade
- to repair skin under the scab, fibrous collagen is deposited and new cells form stem cells in the epidermis
- these new cells are supplied with oxygen and nutrients by the growth of new blood vessels.
state stuff about the primary defence: mucous and membranes
exchange surfaces occur where o2 and nutrients enter the blood are thinner and more exposed to pathogens. e.g lungs and digestive systems
- to protect these surfaces in the airway there are goblet cells which secrete mucus.
- the mucus forms thick mucous membranes which line the passages and trap any pathogens
- the epithelium also contains ciliated cells which have tiny hair like structures called cilia.
- the cilia waft in a coordinated fashion to move mucus with the pathogen trapped in it at the top of the trachea .
- the mucus is then swallowed and enters the stomach where the pathogen is killed by the low PH of stomach acid.
state stuff about the primary defence: expulsive refluxes
-some pathogens can release toxins
-areas that are at risk of infection are very sensitive to pathogens and their toxins.
-when these sensitive areas are irritated, they respond with an expulsive reflex.
- examples: coughing, vomiting, sneezing
it causes air or fluid to be suddenly forced out of the body which carries the pathogen out with it.
what are the non-specific chemical defences
saliva and tears
what do tears and salvia contain and what does it do
their secretions contain an enzyme called lysozyme.
lysozyme kills bacteria by breaking down the cell wall- prevents it from causing disease
state stuff about the innate (non-specific) immune response: inflammation
inflammation is the swelling and redness of a tissue caused by infection.
- inflammation helps destroy invading pathogens.
- first the pathogen is detected in the tissue by mast cells, this causes mast cells to release the cell signalling chemical called histamine
-histamine causes vasodilation which makes the capillary wall in the tissue more permeable to white blood cells
-this allows more white blood cells to get to the site of infection.
vasodilation causes more tissue fluid to be produces and this causes swelling known as oedema, this excess tissue fluid is then drained into the lymphatic system where other immune cells are stored.
these immune cells then attack the pathogens present in the tissue fluid
what are interferons
non- specific defence against viruses, protozoa and some bacteria. infected cells produce interferon which diffuses to surrounding cells where it prevents microbes from multiplying.
inhibits microbial protein synthesis.
whats phagocytosis
when cells engulf and digest pathogens to stop them causing damage
what are the most common examples of phagocytes
macrophages and neutrophils
how are macrophages and monocytes related
a monocyte is a macrophage which hasn’t become a macrophage yet
where are monocytes and neutrophils made
in the bone marrow
monocytes are present in the blood, when do they become macrophages
when they enter the tissue
what do neutrophils do when a pathogen infects a tissue
they arrive and engulf them
state how long macrophages and neutrophils live for and their relationship
neutrophils dies quickly after a few days
monocytes are long lived
- when neutrophils die, the macrophages then arrive at the infected tissue
state the mechanisms of phagocytosis
- phagocyte recognises a foreign marker on the pathogens outer membrane called the antigen.
- small non specific protein molecules attach to the antigen
- the phagocyte can then bind to the opsonin attached to the pathogen antigen
- the pathogen is then engulfed and enclosed in a large vacuole called a phagosome.
- the phagosome fuses with lysosomes which are vesicles containing digestive enzymes called lysozomes
- lysozomes are released and they break down the pathogens structure
- ONLY MACROPHAGES- they save the pathogen antigen
- they are antigen presenting cells, put the pathogen antigen on a special protein complex- moved to the surface membrane so can be recognised
specialisations of a phagocyte
- well developed cytoskeleton to help them change shape to engulf the pathogen and move lysosomes around
- many mitochondria to release energy for cell movement
- lots of ribosomes to synthesise the lysosome enzymes
- lobed nucleus to squeeze between narrow gaps between cells in the tissues
opsonin’s are involved in the ____ ____ ____
innate immune response
whats a neutrophil and what does it have
- a white blood cell- has a pm containing receptors for opsonin’s
- well developed cytoskeleton for phagocytosis
- many mitochondria for respiration
- many ribosomes to make enzymes
what are opsonins
non- specific antibodies, they bind to antigens (they’re markers )
what is the name for white blood cells
leukocytes
what do white blood cells make up
the immune system
4 examples of white blood cells
macrophage, neutrophil, T lymphocytes, B lymphocytes
what do leukocytes do
recognise foreign material and provide immunity against it
what is immunity
the ability of organisms to resist infection by protecting against disease causing microorganisms or their toxins that invade their body
leukocytes ( white blood cells) can be divided into two types, what are the non specific types and what are the specific types
non specific leukocytes:
macrophages, neutrophils
specific leukocytes:
T+B lymphocytes
state basic things about non- specific immunity
made up of macrophages and neutrophils.
produce a response regardless of what the pathogen looks like (phagocytosis)
-provide short term protection.
state basic things about specific immunity
made up of T and B lymphocytes- they come from stem cells in the bone marrow and T mature in Thymus and B mature in bone marrow. lymphocytes have a large nucleus and specialised specific receptors on their pm- provide specific and long term infection.
- specific immune cells produce an adaptive response- this means they adapt their response appropriate for the destruction of a specific pathogen.
- lymphocytes can recognise specific antigens and only produce responses to certain infections- only respond to specific pathogens
what are b lymphocytes responsible for doing
for producing antibodies which are protein molecules to that are specific to an antigen
what can the antibodies form b lymphocytes then do
bind to their specific antigen and neutralise it
what are antibodies present in and what can they bind to
present in the plasma and can bind to specific antigens free in bodily fluids or antigens on cells
what type of immunity are b lymphocytes involved in
involved in humoral immunity- the antibodies are present in body fluids known as humour.
what type of immunity are T lymphocytes involved in
involved in cell mediated immunity.
- t cells have specific receptors on their pm for specific antigens- t cells can only bind to antigens presented on body cells, could be an infected cell ( host cell)e.g
describe the cellular response of lymphocytes
the lymphocyte with the correct receptor has to be found and activated when a specific pathogen invades the body.
- the receptor on the lymphocyte is complimentary to the shape of the antigen
- this contact and activation is called clonal selection.
- this contact is direct ( contact occurs when the lymphocyte comes across the pathogenic cells in the lymph nodes) or indirect (contact occurs when the lymphocyte comes across an antigen presenting cell which phagocytosed the pathogen)
- other immune like cells like macrophages secrete a type of cell signalling molecule called interleukins.
- these interleukins can bind specifically to the selected lymphocyte and cause it to divide by mitosis and produce a lot of clones (clonal selection), slow process
- b make antibodies
- t bind to antigens or antigen presenting cells
what is cell mediated immunity
the recognition of antigens by T cells and the response
what does cell mediated immunity not include
doesn’t include antibodies
A T cell can only detect an antigen if its presented to them via…
via another cell- this is usually a host cell, these are known as antigen presenting cells( examples= infected body cell, transplanted cells, cancer cells.) a T cell cannot recognise an antigen if its free
for there to be a response in cell mediated immunity…
the correct T cell must bind to the specific antigen
what happens after in cell mediated immunity when the correct T cell binds to the specific antigen
the T cell divides by mitosis ( clonal expansion) then starts to specialise into T killer, T helper, T regulatory or T memory
what do t killer cells do
destroy our own body cells infected with the pathogen.
most effective against viruses, makes hole in Pm
what do t helper cells do
release cell signalling molecules called cytokines to help stimulate other immune cells.
- can stimulate phagocytosis and b cells to produce antibodies
what do t memory cells do
remain in the blood for years and provide long term protection- immunological memory
what do t regulatory cells do
inhibit the immune response when the pathogen has been destroyed- slow down immune system so healthy body cells are not damaged
what does humoral immunity refer to
the action of immune molecules which are found in bodily fluids (antibodies are found floating in the bodily fluids)
what does humoral immunity include
includes secreted antibodies (immunoglobins) which are soluble in bodily fluids
humours=_____
fluids
state what happens in the humoral response
to trigger a humoral response, a free antigen/pathogen has to bind to a complimentary receptor on a B cell.
- the pathogen is then endocytosed by the B lymphocyte and the antigen is presented on the Pm.
- T helper cells then bind to the presented antigen and stimulate B cell to divide by mitosis ( cytokines)
- clonal expansion occurs- all clones produce antibody specific to target antigen- they are now plasma cells which can secrete antibodies- antibodies now float in the humour rather than stuck to Pm.
- after clonal expansion, a B lymphocyte can differentiate into a plasma cell or B memory cell
what are the two cells B cells can differentiate into
into a plasma cell or B memory cell
role of plasma cell
specialised to secrete large numbers of antibodies into blood plasma
short lived
role of B memory cell
provide long term protection
-memory b cells do not produce antibodies during og infection however if memory B cell encounters the same antigen in future, they rapidly divide into plasma (clear infection quickly- produce the same antibodies) cells and B memory cells
when the pathogen infects for the first time, how quick is the immune response
slow
whats the primary immune response
the initial response caused by the 1st infection
in the primary response, what occurs
antibodies specific to the pathogens are produced:
- new pathogen enters
- lymphocytes have to detect this and produce response
- to produce antibodies, B cells have to undergo clonal selection and expansion.
- then has to differentiate into plasma or B memory
- plasma produces lots of antibodies
- takes a long time and symptoms usually occur
whats the secondary immune response
a more rapid and vigorous response caused by a second or subsequent infection by the same pathogens.
in the secondary response, what occurs
when same pathogen present, there are already memory cells which recognise it
- memory B cells rapidly differentiate into plasma cells (makes antibodies).
- memory T cells also activated and differentiates into T killer or T helper
why is the scondary response quicker
because clonal selection and clonal expansion are skipped
during lymphocyte development, lymphocytes specific to self- antigens are normally destroyed but…
sometimes they are not causing harm to our own antigens
what is an autoimmune disease
when your immune system mistakenly attacks ur own body
3 examples of autoimmune diseases
arthritis, lupus, myasthenia gravis
an autoimmune disease: arthiritis
antibodies attack membranes around the joint= inflammation
an autoimmune disease: lupus
antibodies attack proteins in nucleus of cells= swelling and pain
an autoimmune disease: myasthenia gravis
attack receptor (essential for reflexes) at neuromuscular joints which causes muscle weakness
definition of immunity
the ability of organisms to resist infection by protecting against disease casing microorganisms or the toxins they produce
2 infections which the immune system is ineffective against…
smallpox
measles
whats vaccinaition
a way of stimulating an immune response so immunity is achieved
- its given as a precaution
- not used to treat people who already have the disease
- mostly protect against infectious diseases
- protect against the non self and specific to a single organism
how does vaccination make the immune system effective
before encounter…
-vaccination makes the immune system more effective by stimulating it to produce specific antibodies and memory cells
later on in life…
when the actual pathogen invades there is a rapid response simmilar to secondary immune response
how does vaccination work, what does it involve
involves deliberately exposing the immune system to the antigen (rendered harmless) of a specific pathogen
- delivered orally or via injection
- immune system produces a response to specific antigen
- b cell stimulated with receptor
- memory cells produced (specific)
- when the actual pathogen invades the vaccinated host, the memory cells differentiate into plasma cells
- infection=rapidly overcome dur to production of antibodies
what are the 4 types of vaccine
- live vaccine
- attenuated vaccine
- dead pathogen
- pathogen fragments
state stuff about live vaccines
contain whole living microorganisms with simmilar antigens to the pathogen.
- the antibodies produced will be effective against the actual pathogen
- live microorganism used is less destructive
state stuff about attenuated vaccines
contain a weak version of the actual pathogen so it cant produce disease but can still multiply
state stuff about dead pathogen vaccines
contain the dead pathogen so the antigen is intact but the pathogen cant cause harm
state stuff about pathogen fragment vaccines
contain only specific antigens that stimulate the immune system
what does a vaccine do to an individual
makes an individual immune to a disease by stimulating their immune system to produce memory cells
if a vaccination is done on a large scale, what does this mean
it can protect populations from disease
what do vaccination programmes involve
vaccinating almost all the population- leads to herd immunity
whats herd immunity
herd immunity occurs when the vaccination of a significant proportion provides protection for individuals who have not developed immunity
when there is no herd immunity, what dos this lead to
people who are not immunised are not protected
what type of people does herd immunity protect
protects non-immunised people because its highly unlikely they will come into contact with an infected person
who is it not possible to immunise
babies
whats ring vaccination
protects against the spread of new diseases as when a new disease is reported everyone in immediate vicinity of the case is vaccinated
why can immunity be lost after being vaccinated
some pathogens can mutate their antigens so memory cells produced by vaccination cannot produce them anymore, this can cause the disease so spread again causing an epidemic
whats an epidemic
the rapid spread of disease through a high proportion of the population
to prevent epidemics, what do vaccines have to do
have to be changed- new modified vaccines specific for mutated antigens are made each year
give an example of a pathogen that as caused an epidemic
the influenza virus that causes the flu
what is immunity
the ability of an organism to resist infection
what are the two types of immunity
active and passive
when does active immunity occur
active immunity occurs when specific antibodies are produced by individuals own immune system
what’s an example of active immunity
- when a person is infected with a pathogen and their immune system produces specific antibodies and memory cells
- when a person is vaccinated and their immune system produces antibodies and memory cells
when does passive immunity occur
passive immunity occurs when specific antibodies are introduced to the individual from an outside source- no direct contact with the specific pathogen is needed to achieve passive immunity
whats an example of passive immunity
when antibodies from the mother are transferred to the baby through breast milk
what are the other two types of immunity
natural and artificial
how is natural immunity achieved
through normal life processes
what’s an example of natural active immunity
immunity through a regular infection
what type of immunity is breastfeeding
natural passive
whats artificial immunity
its induced by medical intervention and the individual does not suffer from any symptoms of disease
an example of artificial active immunity
vaccination
an example of artificial passive immunity
injection of antibodies made by another individual (antibodies from an outside source)
what type of immunity is long term and which is short term
long term=active
short term=passive
explain how vaccines can still work even when not all the population is vaccinated
herd immunity- where enough ( 90%) of a population is immunised to prevent effective pathogen transmission. ring vaccination can also reduce pathogen spread. this is because in both cases the pathogen may not find a new host before being eradicated by an infected persons immune system
