6.3 Disease Defences

Question 1

What are the 2 types of surface barriers in the body?

Answer 1

Skin
Mucous membranes

Question 2

Which glands secrete biochemical defences on the skin?

Answer 2

Sebaceous glands

Question 3

What does skin secrete to lower the pH?

Answer 3

Lactic acid and fatty acids

Question 4

What do mucous membranes secrete as a biochemical defence?

Answer 4

Lysozyme to destroy cell walls and cause cell lysis

Question 5

What is haemostasis?

Answer 5

Clotting - the mechanism by which broken blood vessels are repaired when damaged

Question 6

What are the key components of a blood clot?

Answer 6

Platelets and fibrin stands

Question 7

What occurs in primary haemostasis?

Answer 7

Platelets undergo a structural change when activated to form a sticky plug at damaged regions

Question 8

What occurs in secondary haemostasis?

Answer 8

Fibrin strands form an insoluble mesh of fibres that trap blood cells at the sight of damage

Question 9

What is a coagulation cascade?

Answer 9

The process by which a blood clot forms

Question 10

What is the extrinsic pathway in the coagulation casscade?

Answer 10

Factors released by damaged cells

Question 11

What is the intrinsic pathway in the coagulation casscade?

Answer 11

Factors released by the platelets

Question 12

What are the main events of the coagulation cascade?

Answer 12

Clotting factors cause platelets to become sticky and adhere to the damaged surface
The factors cause localised vasoconstriction and conversion of prothrombin->thrombin
Thrombin catalyses soluble fibrinogen->fibrin (insoluble)
Fibrin forms a mech around the platelet plug and traps blood cells for a temporary clot

Question 13

How are clots broken down?

Answer 13

Plasmin dissolves the clot when damage is repaired

Question 14

What does thrombin do?

Answer 14

Catalyse Fibrinogen (soluble) -> fibrin (insoluble)

Question 15

What do clotting factors do to prothrombin?

Answer 15

Convert it to thrombin

Question 16

If there is a rupture of an atherosclerotic plaque in the coronary arteries what happens?

Answer 16

There will be clotting triggering a thrombus which will block blood flow to cardiac tissue

Question 17

Is the innate immune system specific or non specific?

Answer 17

Non specific

Question 18

What are the principle components of the innate immune system?

Answer 18

Phagocytic white blood cells
(Inflammation
Fever
Antimicrobial chemicals)

Question 19

What are the two key components of the innate immune system?

Answer 19

Non specific
Non adaptive

Question 20

Describe phagocytosis

Answer 20

Process by which solid material is ingested by the cell (endocytosis)

Question 21

Describe phagocytosis

Answer 21

Leukocytes circulate in the blood and move into body tissue in response to infection
Damaged tissue releases chemicals which draw white blood cells to infection site
Pathogens are engulfed when cellular extensions surround the pathogens and fuse to form internal vesicles
The vesicle uses to a lysosome which digests the pathogen

Question 22

What is the name of the cellular extensions that engulf pathogens into phagocytes?

Answer 22

Pseudopodia

Question 23

What name is given to a pathogen fused to a lysosome?

Answer 23

Phagolysosome

Question 24

What may a phagocyte do after digesting a pathogen?

Answer 24

Present the antigen on the surface to stimulate the third line of defence

Question 25

What are the first, second and third lines of defence?

Answer 25

1 - barriers
2 - innate immune system
3 - adaptive immune system

Question 26

What coordinates the adaptive immune system?

Answer 26

lymphocytes

Question 27

What are the 2 types of lymphocytes?

Answer 27

B lymphocytes
Helper T lymphocytes

Question 28

What do B lymphocytes do?

Answer 28

Antibody producing cells that recognise and target specific pathogenic fragments (antigens)

Question 29

What do helper T cells do?

Answer 29

Release cytokines to activate specific B lymphocytes

Question 30

What are cytokines?

Answer 30

Chemicals which activate specific B lymphocytes

Question 31

Describe the activation of the adaptive immune system

Answer 31

Antigens presented by phagocytic leukocytes migrate to the lymph nodes and activate specific helper T lymphocytes
These release cytokines to activate specific B lymphocytes capable of producing antibodies specific to the antigen
Activated B cells will divide and differentiate into short lived plasma cells that produce high amount of specific antibody
A small proportion of activated B cells and helper T cells will develop into memory cells to provide long-lasting immunity

Question 32

What are antibodies composed of?

Answer 32

4 polypeptide chains held together by disulphide bonds in a Y shape

Question 33

Where do antigens bind on antibodies?

Answer 33

On the ends of the arms of the Y

Question 34

What do antibodies do?

Answer 34

Label pathogens for the rest of the immune system

Question 35

What may antibiotics target?

Answer 35

Prokaryote specific cells features
Cell wall synthesis/DNA synthesis/Cell membranes/70s Ribosomes/Metabolic enzymes

Question 36

What are narrow spectrum antibiotics?

Answer 36

Effective against a small range of bacteria

Question 37

What are wide spectrum antibiotics?

Answer 37

Effective against a large range of bacteria

Question 38

When was penecillin discovered and by who?

Answer 38

Fleming in 1928

Question 39

What does HIV stand for?

Answer 39

Human Immunodeficient Virus

Question 40

What does HIV do?

Answer 40

It is a retrovirus that infects helper T cells - disabling the adaptive immune system

Question 41

How does HIV immunity occur?

Answer 41

It occurs in people who lack the CD4+ receptor on T cells

Question 42

How is HIV transmitted?

Answer 42

Exchange of bodily fluids (blood, sexual excretions, breast milk etc…)