12.5 Non-specific Animal Defences Against Pathogens

Question 1

What are non-specific defences?

Answer 1

primary + secondary defences

fighting against GENERAL PATHOGENS.

not specific to a certain type of pathogen.

Question 2

What are 3 barriers to pathogens entering the body?

Answer 2

SKIN

MUCOUS MEMBRANES - trap + remove pathogens

LYSOZYMES - enzymes in tears + urine digesting pathogens

Question 3

What are the non-specific defences which prevent pathogens entering the body?

Answer 3

BLOOD CLOTTING

INFLAMMATORY RESPONSE

Question 4

How does blood clotting occur?

Answer 4

CASCADE of enzyme controlled reactions:

1. Damaged tissue triggers platelets to produce THROMBOPLASTIN
2. thromboplastin catalyses PROTHROMBIN ⟶ THROMBIN
3. thrombin catalyses soluble FIBRINOGEN ⟶ insoluble FIBRIN
4. fibrin forms mesh-like blood clot.

Question 5

What is the function of serotonin in blood clotting?

Answer 5

contracts SMOOTH MUSCLE

to reduce blood flow to area

Question 6

What occurs during the inflammatory response?

Answer 6

MAST CELLS in damaged tissue release…

▪  HISTAMINES 

    - vasodilation >> increases temperature >> inhibit pathogen reproduction.
    - blood vessels more leaky >> more tissue fluid formed to transport phagocytes to cells.

▪  CYTOKINES - attract phagocytes to area

Question 7

What are the non-specific defences which remove pathogens from the internal system?

Answer 7

FEVERS

PHAGOCYTOSIS

Question 8

What is the purpose of a fever?

Answer 8

HYPOTHALAMUS increases temperature:

▪  INHIBITS pathogen reproduction

▪  increases EFFICACY of specific immune system

Question 9

What is phagocytosis?

Answer 9

process by which phagocyte

recognises (due to antigens), engulfs + digests pathogen

in phagolysosome.

Question 10

What occurs during phagocytosis?

Answer 10

1. Phagocyte IDENTIFIES pathogen due to foreign ANTIGENS.
2. ENGULFS pathogen + encloses in PHAGOSOME.
3. lysosome + phagosome combine ⟶ phagolysosome. (hydrolytic enzymes digest pathogen)
4. Pathogen’s antigens + MHC ⟶ MHC-antigen complexes
5. MHC-antigen complex attaches to plasma membrane ⟶ APC, antigen presenting cell.

Question 11

What is an antigen presenting cell?

Answer 11

cell which DISPLAYS MHC-FOREIGN ANTIGEN COMPLEXES

on their surfaces.

Question 12

What is the purpose of an antigen presenting cell?

Answer 12

STIMULATES other immune cells

e.g produce antibodies/antitoxins/interleukins

Question 13

What do histamines do?

Answer 13

VASODILATION

make blood vessels more LEAKY

Question 14

What do cytokines do?

Answer 14

ATTRACT PHAGOCYTES to site of infection.

Question 15

What do opsonins do?

Answer 15

BIND to pathogen’s antigens

SIGNPOSTING it to phagocytes