The Immune System

Question 1

function of the immune system

Answer 1

to protect the body against infection by preventing pathogens from entering the body and destroying pathogens

Question 2

first line of defence

Answer 2

physical, chemical, microbial barriers which aim to prevent entry of pathogens

non-specific

Question 3

physical barriers

Answer 3

trap/prevent entry to internal organs

skin - epidermis, keratin, dead cells, hairs

hair e.g. nose, eyelashes

ear wax

mucous membranes - traps

Question 4

chemical barriers

Answer 4

natural secretions -> trap/destroy

tears/saliva = enzymes which break down bacteria

stomach acid -> HCl -> destroy

sweat -> salts -> hostile environment for bacteria

sebum -> contains bactericidal +fungicidal properties -> decreased bacteria on skin

Question 5

microbial barrier

Answer 5

natural flora

bacteria = non-pathogenic, restricts space for growth of pathogenic bacteria by outcompeting for space/resources

Question 6

innate/non-specific immunity

Answer 6

1. inflammation
2. phagocytosis

response = same for all pathogens

level of response = same regardless of threat

no memory

immediate response

Question 7

process of inflammation

Answer 7

non-specific response triggered when 1st line is broken ->
damaged cells release chemical signals e.g. histamine ->
vasodilation/increased permeability of blood capillaries causing increased blood to area as well as increased leakage of WBC and plasma to surrounding tissue ->
more phagocytes to injury/swelling -> pain/heat/redness

Question 8

process of phagocytosis

Answer 8

phagocyte recognizes bacteria as non-self ->
phagocyte engulfs pathogen ->
phagosome formed -> phagolysosome formed ->
enzymes w/in lysosome breakdown pathogen ->
unwanted debris removed from cell

Question 9

pathogen

Answer 9

disease causing agent

Question 10

antigen

Answer 10

specific surface marker on pathogens that can be detected by WBC

Question 11

antibody

Answer 11

protein produced in response to counteract a specific pathogen

Question 12

adaptive/specific immunity

Answer 12

1. cell mediated response (T lymphocytes)
2. humoral response (B lymphocytes)

response = specific for each pathogens

level of response = increases over infections

memory

delayed response

Question 13

lymphocytes

Answer 13

general term for a range of specialised white blood cells that respond to specific antigens

Question 14

B lymphocytes, B plasma, B memory cells

Answer 14

WBC produced in the bone marrow, travel to the spleen and lymph nodes

Plasma cells = B lymphocytes that secrete specific antibodies

Memory cells = give long term memory of specific antigen, long lived

Question 15

Cytotoxic T cells, Helper T cells

Answer 15

cytotoxic - T cells that contain lethal chemicals that destroy foreign, infected and altered cells

helper - T cells that help or activate the other cells of the immune system by releasing cytokines

Question 16

dendritic cells

Answer 16

cells with membranous extensions, attract antigens and present to T helper cells

Question 17

macrophage

Answer 17

phagocytic cell -> engulf and destroy pathogen (2nd line) -> antigen presenting cell (3rd line)

Question 18

how do antibodies work

Answer 18

1. bind with antigen -> deactivate
2. form lattice (agglutinates) -> signal for phagocytosis
3. signal release of cytotoxins
4. immobilize pathogens

Question 19

active immunity

Answer 19

antibodies produced within individual

natural -> response to infection

induced -> vaccinations

Question 20

passive immunity

Answer 20

antibodies produced in one individual, introduced into another

natural -> maternal antibodies through placenta

induced -> plasma donation (injected with antibodies)