4.1.1 Diseases - responses bit Flashcards
what causes communicable diseases?
pathogens
Types of pathogen
bacteria
viruses
fungi
protocista
Tuberculosis (TB)
bacteria
affects human and cattle (typically)
Meningitis
Bacteria
affects humans
Ring rot
bacteria
potatoes, tomatoes
HIV / AIDS
virus
humans
Influenza
virus
animals (including humans)
Tobacco Mosaic Virus
virus
plants
Black sigatoka
fungus
banana plants
Ring worm
fungus
cattle
Athlete’s foot
fungus
humans
Potato / tomato blight
protocitist
potatoes / tomatoes
Malaria
protoctist
animals (including humans)
Direct transmission
when a disease is transmitted directly from one organism to another
How can direct transmission happen:
- direct contact
- inoculation
- ingestion
direct transmission - direct contact
contact with bodily fluids
- blood, semen, vaginal or infected individuals
skin to skin contact
microorganisms from faeces transmitted on hands
direct transmission - inoculation
through a break in the skin
from an animal bite
through a puncture wound sharing needles
Indirect transmission
when a disease is transmitted from one organism to another via an intermediate
How can indirect transmission happen:
- fomites
- droplet infection
- vectors
Indirect transmission - fomites
through inanimate objects
bed, clothes, cosmetics
indirect transmission - droplet infection
tiny drops of saliva and mucus transfer pathogens during talking, coughing and sneezing
indirect transmission - vectors
transfer pathogens from one organism to other
animals and water
factors affecting transmission
- living conditions
- crowding
- social factors
factors affecting transmission - living conditions
overcrowded living conditions increase the transmission of diseases
eg. TB spread via droplet infection, increased risk of infection and spread if lots of people in an area
factors affecting transmission - climate
potato and tomato blight especially common during wet summers
- because the spores need water to spread
malaria most common in tropical countries (humid and hot)
- ideal conditions for mosquitoes (malaria vectors) to breed
factors affecting transmission - social factors
eg. risk of HIV high in places where there’s limited access to
1. good healthcare
- people less likely to be diagnosed and treated for HIV
- most effective anti-HIV drugs are less likely to be available
- virus more likely to be passed onto other
- good health education
- to inform people about how HIV is transmitted and how it can be avoided
eg. safe sex practices - condoms
Animals defense against disease:
skin mucous membrane blood clotting inflammmation wound repair expulsive reflexes
Animals defense against disease - skin
acts as a physical barrier, blocking pathogens from entering the body
acts as a chemical barrier, produces chemicals that are antimicrobial and can lower pH, inhibiting growth of pathogens
Animals defense against disease - mucous membranes
protect body openings that are exposed to the environment (mouth, nostrils, ears)
some membranes secrete mucus - a sticky substance that traps pathogens and contains antimicrobial enzymes
Animals defense against disease - blood clotting
a mesh of protein fibres
plug wounds to prevent pathogen entry and blood loss
formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels
Animals defense against disease - inflammation
swelling, pain, heat and redness
triggered by tissue damage - the damaged tissue releases molecules which increase the permeability of the blood vessels, so they start to leak fluid into the surrounding area
this causes swelling and helps to isolate any pathogens that may have entered the damaged tissue
these molecules also cause vasodilation which increases blood flow to the affected area
- this makes the area hot and brings white blood cells to fight off pathogens that may be present
Animals defense against disease - wound repair
skin is able to repair itself and reform barrier against pathogen entry
the surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound
the tissue below the wound then contracts to bring the edges of the wound closer together
its is repaired using collagen fibres - too many collagen fibres = scar
Animals defense against disease - expulsive reflexes
coughing and sneezing
sneeze - when mucous membrane in the nostrils are irritated by dirt or dust
cough - irritation is respiratory tract
an attempt to expel foreign objects, pathogen, from the body
AUTOMATIC
Plants defenses against disease:
physical
chemical
Plants defenses against disease - physical
- waxy cuticle - barrier to pathogen entry - stops water collecting on leaf which could reduce infection by pathogens that are transferred between plants in water
- cell walls - barrier to pathogens that make it past waxy cuticle
- callose - a polysaccharide that is deposited between plant cell walls and plasma membranes during times of stress (pathogen invasion) - makes it harder for pathogens to enter cells - callose deposition at the plasmodesmata may limit spread of virus between cells
Plants defenses against disease - chemical
- produce antimicrobial chemicals (including antibiotics) which kill pathogens or inhibit their growth
- saponins —> destroy cell membranes of fungi and other pathogens
- phytoalexins —> inhibit growth of fungi and other pathogens - secrete chemicals that are toxic to insects - reduces the amount of insect-feeding on plants and therefore reduces the risk of infection by plant viruses carried by insect vectors
what triggers an immune response
foreign antigens
what are antigens
molecules on the surface of cells
its how body identifies cell as foreign
what is the non-specific immune response?
phagocytes engulf pathogens - PHAGOCYTOSIS
- a phagocyte recognise the antigens on a pathogen
- the cytoplasm of the phagocyte moves around the pathogen, engulfing it.
- made easier by opsonins —> molecules in the blood that attach to forgein antigens to aid phagocytosis - the pathogen is now contained in a phagosome (a vesicle) in the cytoplasm of the phagocytes
- a lysosome (organelle that conatins digestive enzymes) fuses with the phagosome
- the enzymes break down the pathogen - the phagocytes then presents the pathogens antigens
- it sticks the antigens on its surface to active other immune system cells
- acts as an antigen-presenting cell
what are opsonins
a molecule in the blood that attach to foreign antigens to aid phagocytosis
work in different ways
- some hide the negative charges on the membrane of the pathogen, making it easier for the negitevly charged pharged phagocytes to get closer to the pathogen
what is a phagocyte
a type of white blood cell that carries out phagocytosis
found in blood and tissues and carry out the non-specific immune response
what are neutrophils
a type of phagocyte
the first white blood cells to respond to a pathogen inside the body
move towards a wound in response to signals from cytokines
the cytokines are released by cells at the site of the wound
specific immune response - 3 main stages
- phagocytes activates T lymphocytes
- T lymphocytes active B lymphocytes, which divide into plasma cells
- plasma cells make more antibodies to a specific antigen
specific immune response - phagocytes activates T lymphocytes
- a T lymphocyte is another type of white blood cell
- their surface is covered with receptors
- the receptors bind to antigens presented by antigen-presenting cells
- each T lymphocyte has a different receptor on its surface
- when the receptor on the surface of a T lymphocyte meets a complementary antigen, it binds to it
- –> so each T lymphocyte will bind to a different antigen - this activates the T lymphocyte —> CLONAL SELECTION
- the T lymphocyte then undergoes CLONAL EXPANSION - it divides to produce clones of itself
- different types of T lymphocytes carry out different functions
different types of T lymphocytes
- T helper cells - these release substances to activate B lymphocytes and T killer cells
- T killer cells - these attach to and kill cells that are infected with a virus
- T regulatory cells - these suppress the immune response from other white blood cells
- this helps stop immune system cells form mistakenly attacking the hosts’s body cells
specific immune response - T lymphocytes activate B lymphocytes
- B lymphocytes are covered with protiens called antibodies
- antibodies bind to antigens to form an antigen-antibody complex
- each B lymphocyte has a different shaped antibody on its surface
- when then antibody on the surface of a B lymphocyte meets a complementary shaped antigen, it binds to it
- so each B lymphocyte will bind to a different antigen - this, together with substances released from T helper cells, activates the B lymphocyte
- –> CLONAL SELECTION - the activated B lymphocyte divides, by mitosis, into plasma cells and memory cells
- —> CLONAL EXPANSION
specific immune response - plasma cells make more antibodies to a specific antigen
- plasma cells are clones of the B lymphocytes
- they secrete loads of the antibody, specific to the antigen, into the blood
- these antibodies will bind to the antigens on the cell surface of the pathogen to form lots of antigen-antibody complex
structure of antibodies
Variable regions - form the antigen binding sites (differ between antibodies)
- the shape of the variable region is complementary to a particular antigen
Hinge region - allows flexibility when the antibody binds to the antigen
Constant region - allow binding to the receptor on immune system cells
- is the same in all antibodies
Disulfide bridges - the bond that hold the polypeptide chains of the protein together
cell signalling
how cells communicate
a cell may release a substance that binds to the receptors on another cell - causes a response
why is cell signalling important in the immune response
helps to activate all the different types of white blood cells that are needed
cell signalling - interleukins
a type of cytokine
binds to receptors on B lympocytes
this activates the B lymphocytes
eg. T helper cells signal to B lymphocytes that there’s a pathogen in the body
How do antibodies help clear infection:
- agglutinating pathogens
- neutralising toxins
- preventing the pathogen binding to the human cells
How do antibodies help clear infection - agglutinating pathogens
each antibody has two binding sites
so an antibody can bind to two pathogens at the same time
the pathogens become clumped together
phagocytes then bind to the antibodies and engluf lots of pathogens all at once
How do antibodies help clear infection - neutralising toxins
toxins have different shapes
antibodies called anti-toxins bind to the toxins produced by pathogens
this prevents toxins from affecting human cells, so toxins are neutralised
the toxin-antibody complexes are also phagocytosed
How do antibodies help clear infection - preventing the pathogens binding to human cells
when antibodies bind to the antigens on the pathogens, they may block the cell surface receptors that the pathogens need to bind to the host cells
so the pathogens cant attach to or infect the host cells
primary response
slow
- when a pathogens enter the body for the first time the antigens on its surface activates the immune system
- arent many B lymphocytes that can make make the needed antibody
- eventually body will produce enough of the right antibody to overcome the infection
- –> meanwhile the infected person will show symptoms of the disease - after being exposed to an antigen —> T and B memory cells
- the person is now immune - immune system has the ability to respond quickly to a second infection
T and B memory cells
remain in the body for a long time
remember the specific antigen and will recognise it a second time round
memory B record the specific antibodies needed to bind the antigen
Secondary response
if the same pathogen enters the body again, the immune system will produce a stronger, quicker immune response
clonal selection happens faster
- –> memory B activated and divide into plasma cells that produce the right antibody to the antigen
- –> memory T activated and divide into the correct type of T lymphocyte to kill the cell carrying the antigen
gets rid of symptoms before you begin to show any symptoms
blood smears - what do you see
red blood cells - dont have a nucleus
platelets - fragments of cells
white blood cells:
Lymphocyte - smaller than neutrophil, nucleus takes up most of the cell, little cytoplasm + not grainy
Neutrophil - nucleus looks like three interconnected blobs (multi-lobed), cytoplasm grainy
Monocyte - biggest wbc, type of phagocyte, kidney bean shaped nucleus, cytoplasm not grainy
