assessment 3 Flashcards
define infectious disease
disease which can be transmitted from one organism to another, and are caused by pathogens
define pathogen
any organism capable pf causing disease
list the 5 types pathogens
bacteria fungi protozoans viruses prions
define bacteria
prokaryotic, unicellular organisms, which don’t have membrane bound organelles and are each made of one cell.
pathogenic bacteria can cause disease, usually by releasing toxins or damaging host issues.
example of a bacteria that causes disease
tuberculosis - caused by the bacterium mycobacterium tuberculosis, the bacteria enters the lungs when a person inhales infectious droplets
define fungi
eukaryotic, non-photosynthetic, hetertrophic organisms with a cell wall. Can be unicellular or multicellular
The damage caused by fungi mostly arises from the enzymes they produce.
example of fungi that causes disease
TINEA
Mode of transmission = direct contact, skin to skin contact, surfaces e.g. shower floor
The fungi lives in the outside the layer of the human skin, where they produce chemicals which break down keratin
define protozoans
unicellular microorganisms wiht internal membranes. Eukaryotic with a complex lifestyle.
example of a protozoan that causes disease
MALARIA
caused by plasmodium
- plasmodium floasts freely int he blood of an infected person, it feeds on haemoglobin in the RBC’s causing them to pop
define viruses
non-cellular entities (non-living), consisting og a single type of nucleic acid (RNA or DNA) encased in a protein coat.
how does viruses reproduce
The virus attaches to a host cell, which it then penetrates. It hijacks the hots enzymes and nutrients to make its own viral proteins and nucleic acid
- The viral materials assemble into new viruses which are released from the host cell and infects other cells
example of a virus that causes disease
COVID 19
define prions
protein that has been altered from its normal structure and can then alter other proteins to develop more prions, so that change spreads like a chain reaction
what tissues does prions normally affect
brain and neural tissue - leads to neurodegeneration
example of a prion that causes disease
SPONGIFORM ENCEPHALOPATHY (MAD COW DISEASE) IN CATTLE Progressive, degenerative and fatal disease affecting the central nervous system in cattle HUMAN FORM = CREUTZFELDT-JAKOB DISEASE symptoms incl. loss of intellect, changes in personality, loss of co-ordination
what are the 3 modes of transmission
- direct contact
- indirect contact
- vector
what is direct contact (mode of transmission)
physical contact between an infected organism and a susceptible organism allows the transfer of infected bodily fluids
types of direct contact include …
person to person
droplet spread
e.g. of diseases that come from person to person contact (direct)
STD’s, ring worm, needle injections
e.g. of diseases that come from droplet spread (direct contact)
tuberculosis, measles, small pox
what are types of indirect contact
airborne
contained object (fomites)
contaminated food and drinking water (vehicular)
explain fomites as a type of indirect contact + e.g.
when organisms can live on objects or a short period of time e.g. door knob, railing…
E.G. E. Coli
explain vehicular transmission + e.g.
transmission through contaminated food and water
E.G. E. Coli
what are vector borne
the transfer of the pathogen via another object such as an insect
vector transmission example
malaria
caused by plasmodium
plasmodium is a pathogen that floats in the blood of an infected persona and needs on haemoglobin causing RBC to pop
how did koch build on germ theory
koch isolated and gre the bacteria responsible for causing anthrax
what is kochs postulates?
list of criteria which must be met to prove that a particular organism causes a particular disease
list kochs postulates
- in every case
- must be able to be grown in pure culture
- same symptoms as the original host - (disease must be able to be reproduced)
- the disease must be able to be produced
what theory did pasteur have the idea of
microbial fermentation theory
what is pasteurisation
a technique to kill the germs he had discovered, by boiling the wine before cooling it
what is the goal of the barriers of infection
to prevent pathogens from entering your body
what are the three types of barriers of infection
physical, chemical, microbiological
define physical barriers (of infection)
barriers which physically block a pathogen from entering your body
examples of the physical barriers to infection
skin, mucus membranes, cilia, urine, saliva, eyelids
how does mucus membranes act as a physical barrier to infection
Mucus membranes line the openings of your body which arent covered in skin E.G. Respiratory, digestive, reproductive and urinary
- prevents membranes from drying out
- traps unwanted pathogens and substances until they can be removed from cilia
- contains lysozyme to help break down microbes
how does cilia act as a physical barrier to infection
cilia is small hair-like projections that extend from the epithelial cells and line the respiratory tract
how does saliva act as a physical barrier to infection
swallowing saliva washes microbes from the teeth and mouth
how does eyelids act as a physical barrier to infection
wipes pathogens away
define chemical barriers (barriers of infection)
chemical barriers make the body surfaces inhospitable to pathogens
how does lysozyme act as a chemical barrier to infection
lysozyme is an enzyme that breaks down the cell walls of bacteria, killing them and helping to fight infection
found in tears, saliva, mucus
how does acidic secretions act as a chemical barrier to infection
they contain degradative enzymes like lysozy,e
body secretions also chemically screen out pathogens by being very acidic (low pH)
acid secretions are produced in vagina, ear canal, stomach, skin
define microflora
microorganisms in our body which dont cause harm
what does microflora aid our body
- compete for space and nutrients. The body has space for pathogens to live and grow in food and to feed off. A pathogen doesn’t have a chance to establish itself in the body because it is already being used by microflora
- produce antimicrobial chemicals
antimicrobial chemicals which prevent the growth of other organisms. The acidity of the skin results from the activity of microflora, which break own the sebum your skin to form fatty acids.
what is the goal in the innate immune system
to stop foreign materials spreading around the body and causing more damage.
characteristics of innate system
- non-specific
- responds rapidly
- doesn’t adapt hence innate
what are the components of the innate immune system
phagocytosis
natural killer cells
inflammation
the complement system
define phagocytosis
the process by which phagocytes engulf and destroy foreign or unwanted material
e.g. pathogens
what are phagocytes
WBC or leukocytes. WBCs are designed to protect the body against invaders
what are the phagocytes e.g.s
neutrophils
macrophages
mast cells
what are the steps in phagocytosis
- the phagocyte engulfs the foreign material, forming a phagosome
- a lysosome fuses with the phagosome, forming a phagolysosome
- within the phagolysosome the enzymes break down the foreign material into smaller pieces
- the small waste fragments are expelled from the phagocyte by exocytosis. this residual vesicle fuses with the plasma membrane and the contents are released.
what are neutrophils involved in
PHAGOCYTOSIS
- quickly enter tissues and phagocytose pathogens in acute infection
ANTIMICROBIAL COMPOUNDS
- release hydrogen peroxide which disrupts bacterial and fungal cell membranes killing
RELEASE CYTOKINES
which attract other immune cells and promote inflammation
what are macrophages involved in
PHAGOCYTOSIS
they live longer than other phagocytes so they help fight chronic infections
ANTIGEN PRESENTATION
Present some antigenic fragments on their surface. It then meets up with T lymphocytes and activated them
RELEASE CYTOKINES
what are dendritic cells involved in
phagocytosis
antigen presentation
what are natural killer cells
they constantly patrol the body, and are important in the defence virus-infected and cancerous cells
what do natural killer cells do
- they release cytotoxic chemicals (chemicals which can kill cells directly)
- they only release cytotoxic chemicals when they’re in close proximity to the target cells
e.g. of natural killer cells
perforin - punches holes in the cell membrane of the target cell, killing it
what is inflammation
the accumulation of fluid, plasma proteins and white blood cells that occurs when tissue is damaged or infected
symptoms of inflammation
redness, heat, swelling, pain, loss of function in the affected area
steps in the inflammatory response
the pathogen successfully makes it through the first line of defence or the body tissues get damaged.
injured cells release chemokines (chemokine have many functions incl. attracting neutrophils
what are the goals of inflammation
confine the pathogen to one area
destroy the pathogen
remove the pathogen, its products and any damaged tissue
what is the complement system
a set of more than 30 different proteins which float around in the blood
when is the complement system activated
when the pathogen breaks through the barriers to infection
what are results of the complement system
- punching holes in the cell membrane or wall of the pathogen
- promoting inflammation
- opsonisation, where these proteins flag the antigen for removal
what are the two types of immunity involved in the adaptive immune system
antibody-mediated
cell-mediated
what are B lymphocytes
a type of WBC which is produced int he bone marrow
explain the lifecycle of B lymphocytes
- they are produced and mature in the bone marrow
- once matured they are released in to the blood
- they accumulate in the lymphoid tissues
- when a b lymphocyte comes into contact with a specific antigen it becomes activated
- once triggered by an antigen, it begins to proliferate to form millions of clones
list the two types of B lymphocytes
plasma cells
memory B lymphocytes
what is the function of plasma cells
- produces antibodies that either: make the pathogen unable to cause damage or makes it easier for other components of the immune system to destroy it.
- proteins which bind to specific antigens
list 4 antibody strategies
neutralisation
precipitation
agglutination
activating complement system
what is the antibody strategy of neutralisation
deactivating a pathogen or toxin by blocking its active site
what is the antibody strategy of precipitation
antibodies bind to soluble anitgens causing them to form insoluble clumps
what is the antibody strategy of agglutination
antibodies bind to antigens on the surface of cells to form clumps of cells
what is the antibody strategy of activating complement system
to help disarm pathogens, enhancing phagocytosis, inflammation and pathogen removal by cell lysis
what is the function of memory B lymphocytes
- provides immunological memory
- acts as a long term defence against antigens
how does memory b lymphocytes work
- If the animal is exposed to the same antigen again, memory cells recognise it can divide to produce antibody-producing plasma cells
benefits of memory b lymphocytes
faster
stronger
longer lasting
as the body has already met the antigen before
what cell is involved in cell-mediated immunity
t lymphocytes
what cell is involved in antibody mediated immunity
b lymphocytes
what are t lymphocytes
a type of WBC which is produced in the bone marrow
explain the life cycle of T lymphocytes
- produced in bone marrow
- they are released into the blood and mature in the thymus gland
- once they mature, theyre released into the blood again where they circulate in an inactive state
- if a T lymphocyte comes into contact with its specific antigen, the receptors on its surface allows it to bind it and the cell becomes activated.
list the types of T lymphocytes
cytotoxic (killer T cells)
helper
supressor
memory
what is the function of T lymphocytes
kill foreign, infected and abnormal cells
they also sometimes kill the body’s own cells
cytotoxic T lymphocytes secrete or inject toxic chemicals into the target cells
function of helper T lymphocytes
- Help promote the activities of other immune responses
- Secrete cytokines which:
1. Increase the activity of phagocytes
2. Help promote inflammation
3. Stimulate the production of cytotoxic T lymphocytes
4. Stimulate B lymphocytes to differentiate to form plasma cells and memory B lymphocytes
function of supressor T lymphocytes
- Turn off the immune response after the antigen has been successfully contained, destroyed or removed
function of memory T lymphocytes
- Provide the body with long term defence against antigens
what is an antigen
any molecule that the body recognises as foreign and that triggers an immune response
what is immunity
the ability to recognise foreign substances, and destroy them
