B4 - Disease Flashcards
Transmission:
How can being in a hot climate make transmission more likely?
increased heat provides more kinetic energy for chemical reactions and reproduction
Transmission:
How can social factors such as poverty and developing countries make transmission more likely?
could result in poor sewage infrastructure, no fresh water/food, bad sanitation and overcrowded living. Medicines/vaccines might be less available.
Types of Direct transmission in Animals?
- Direct contact
- Inoculation
- Ingestion
Direct Transmission: how can direct contact be a form of transmission?
touching, kissing, contact with cuts in skin and sex
Types of Indirect transmission in Animals?
- Vectors
- Droplets
Direct Transmission: how can inoculation be a form of transmission?
touching, kissing, contact with cuts in skin and sex
Direct Transmission: how can ingestion be a form of transmission?
drinking and eating contaminated things
Indirect Transmission: how can a vector be a form of transmission?
animals that pass the pathogen to humans, e.g. mosquitoes’ malaria
Indirect Transmission: how can droplets be a form of transmission?
pathogens transmitted in droplets of water.
e.g. saliva and mucus expelled when sneezing
Indirect Transmission: how can fomites be a form of transmission?
dirty bedding, socks and cosmetics are examples of inanimate objects that can carry and transmit pathogens
What modes of direct transmission are there in plants?
direct contact - between diff plants.
e.g. ring rot and tobacco mosaic virus
what modes of indirect transmission are there in plants?
- contaminated soil
- vectors
Indirect transmission: how is contaminated soil a form of transmission?
pathogens and their spores can remain in soil and infect roots of plants
Indirect transmission: how are vectors a form of transmission?
wind, water, animals and humans can carry pathogens and spores from one plant to another
Plant responses: how do plants prevent entry of diseases?
they have barriers such as bark or waxy cuticles
Plant responses, what do plants have?
- barriers to prevent entry, e.g. bark/waxy cuticles
- antibacterial chemicals and proteins act as a defence against bacterial infections. Can repel insects (vectors) snd kill pathogens
- physical defences to prevent pathogens from spreading between cells, e.g. callose
Animal responses; what is the primary line of defence?
It is non-specific
Animal responses; how is the skin a primary line of defence?
- it is a physical barrier
- contains skin flora (healthy microorganisms), outcompete pathogens for space and resources on the skin
Animal responses; how are blood clots a primary line of defence?
- blood clots will form if the skin is cut to form a new barrier
Animal responses; how are mucous membranes a primary line of defence?
- line many body tracts
- mucus produced traps pathogens and the cilia sweep the mucus away from lung
Animal responses; how are lysozymes a primary line of defence?
- hydrolytic enzyme which digest pathogens
Animal responses; how are expulsive reflexes a primary line of defence?
- sneezing, coughing, vomiting
- mechanisms to force pathogens out of the body
Animal responses; how is inflammation a primary line of defence?
- occurs in localised areas where damage to cells is detected.
- it causes the area to become red, hot, sore, itchy and swollen
- when cells are damaged, it triggers mast cells to release histamines and cytokines
Animal responses; how are histamines a primary line of defence?
- cause blood vessels to dilate and therefore more blood is flowing to area
- the increased temp from blood can kill pathogens.
- make walls of blood vessels more permeable so more white blood cells can be delivered to the site of damage.
Animal responses; how are cytokines a primary line of defence?
- attract phagocytes, which can engulf and destroy pathogens
What is phagocytosis?
Phagocytes, travel in the blood and squeeze out of capillaries to engulf and digest pathogens. it is a non-specific response
What is the process of phagocytosis?
- damaged cells and pathogens release cell signalling chemicals (cytokines) that attract the phagocytes to the site of infection
- an opsonin protein can attach to pathogens to mark them and make it easier for neutrophils and macrophages to engulf them
- phagocytes have receptors which can attach onto chemicals on the surge of pathogens
- the phagocyte then engulfs the pathogen into a vesicle to create a phagosome
- within the phagocytes, there are lysosomes which contain hydrolytic lysozyme
- the lysosome fuses with the phagocytes to expose the pathogen to the lysozyme. The lysozyme hydrolyses the pathogen and any soluble useful molecules are absorbed into the cytoplasm of the phagocyte
- the phagocytes will present the antigen if the digested pathogen on their surface (antigen-presenting cells)
what’s the second line of defence?
It is specific and responds to antigens.
There are two types:
- B lymphocyte (B cells)
- T lymphocytes (T cells)
where are B cell and T cells created?
Both created in bone marrow stem cells, but B cells mature in bone marrow whereas T cells mature in thymus
what are T cells reponsible for?
cell mediated repsonse
how do T cells respond?
Receptors on T cells bind to antigens on antigen-presenting cells (APCs).
This will cause T cell to divide by mitosis (clonal expansion).
APCs are cells that present a non-self antigen on their surface.
What do these include?
- infected body cells presenting viral antigens on their surface
- a macrophage which has engulfed and destroyed a pathogen presenting the antigens on their surface
- cells of transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens
- cancer cells will have abnormal-shaped self-antigens
what is the cell mediated response?
- once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are positioned on the cell surface. this is now called an APC
- T helper cells have receptors on their surface which can attach to the antigens on APC
- once attached, interleukins are produced which activates the T helper cells to divide by mitosis to replicate and make large numbers of clones
- cloned T helper cells differentiate into diff cells
What are the different cells that T helper cells differentiate into?
- T helper cells and produce interleukins to activate B lymphocytes
- some produce interleukins to stimulate macrophages to perform more phagocytosis
- T memory cells for that shaped antigen
- T killer cells
- T regulator cells, which suppress the immune response to ensure the cell-mediated response only occurs when pathogens are detected.
What are T killer cells
can destroy abnormal or infected cells.
most common in viral infections because viruses infect body cells, body cells are sacrificed to prevent viral replication
How do T killer cells destroy cells?
release a protein, perforin, which embeds in the cell surface membrane and makes a pore so that any substances can enter or leave the cell and this causes death.
What is the humeral response?
T helper cells stimulate the B cells by producing interleukins.
This initiates the humeral response, which involves antibodies.
What is an antibody?
- globular, quaternary proteins that have binding sites complementary in shape to antigens.
- they are made up of 4 polypeptide chains, 2 heavy polypeptide chains and 2 light polypeptide chains.
- its binding site is the variable region, where the antibody binds to a complementary-shaped antigen
- the rest of the antibody is the constant region
- when antigen and antibody bind its known as an antigen-antibody complex
What 3 ways do antibodies work in?
- agglutination
- marking pahtogens
- anti-toxins
Antibodies; what is agglutination?
the climbing together of pathogens to make it easier for phagocytes to locate and engulf them