Ch 12

Question 1

Non-specific animal defences against disease?

Answer 1

Skin prevents entry of pathogens & produces sebum; oily substance that inhibits growth of pathogens.

Body tracts lined with Mucous Membranes; secrete sticky mucous to Trap Microorganisms - mucous contains Phagocytes and Lysozymes to Destroy them. Expulsive Reflexes Eject pathogen-laden Mucous.

Lysozymes in tears and acidic pH of stomach kills pathogens upon entering body.

Question 2

Outline why Blood clotting and Wound repair essential?

Answer 2

If skin is breached pathogens can enter body, so Blood clots Rapidly to Seal.
If Platelets come in contact with Collagen in Skin or damaged Vessel wall, they Adhere and Secrete substances such as:
Thromboplastin & Serotonin

Question 3

What substances are secreted when platelets come in contact with collagen of skin or broken vessel wall?

Answer 3

Thromboplastin - Enzyme Triggers cascade of Reactions that results in Blood Clot Formation.
Serotonin - causes Smooth Muscle in walls of blood vessels to Contract so they Narrow to Reduce Blood Supply to area; Reducing Blood Loss.

Question 4

Blood clot formation:

Answer 4

Platelets come into contact with broken skin/vessel wall = secrete Thromboplastin & Serotonin.
Clot dries, forming tough scab to keep pathogens out. (1st stage wound repair)
Epidermal cells (bellow scab) grow to seal wound Permanently.
Damaged blood vessels regrow.
Collagen fibres are deposited to give the new tissues strength.
Once the new epidermis is thick and strong enough, scab comes off = wound healed.

Question 5

Inflammatory response: what is it?

Answer 5

The inflammatory response = localised response to pathogens, resulting in inflammation at site of wound.
Inflammation is characterised by: pain, heat, redness, swelling of tissue.

Question 6

What are Mast cells?

Answer 6

Mast cells = type of white blood cell.

Mast cells are activated in damaged tissue and release chemicals called histamines and cytokines.

Question 7

What are Histamines?

Answer 7

Histamines make the blood vessels dilate (widen), causing localised heat and redness.
Heat/Raised Temperature helps prevent pathogens reproducing.
(Released by mast cells)

Question 8

What are cytokines?

Answer 8

Cytokines act as cell-signalling molecules, attracting white blood cells, specifically phagocytes, to the site of infection to destroy the pathogens by phagocytosis.

Question 9

Non-Specific Animal Defences; Destroying Pathogens

Answer 9

Fevers; raised body temperature above normal, 38°C+. = inhibits pathogen reproduction.
Cytokines stimulate hypothalamus to increase body temperature

Question 10

What is Phagocytosis?

Stages of phagocytosis?

Answer 10

Neutrophils and Macrophages = Phagocytes.
1) pathogen produces chemicals that attract phagocytes.
2) pathogen is recognised as non-self due to its foreign antigens.
3) phagocyte engulfs pathogen.
4) pathogen is enclosed in a vacuole called a Phagosome.
5) Phagosome vacuole combines with a Lysosome, forming a Phagolysosome.
6) pathogen is broken down by enzymes from lysosome.
MACROPHAGE presents the Pathogen’s antigens are displayed on the phagocyte = Antigen Presenting Cell. This attracts and stimulates other immune cells.

Question 11

What are Opsonins?

Answer 11

Opsonins = chemicals the bind to pathogens and “tag” them for easy recognition by phagocytes.
Phagocytes have Opsonin receptors on their cell surface membranes so bind and engulf the pathogen (start of phagocytosis).
There are many opsonins; e.g. IgG Immunoglobulin G, and IgM Immunoglobulin M

Question 12

Types of T Lymphocytes

Answer 12

T helper cells
T killer cells
T memory cells
T regulator cells

Question 13

Main types of B Lymphocytes

Answer 13

Plasma cells
B effector cells
B memory cells

Question 14

T Helper Cells

Answer 14

T helper cells have CD4 receptors on their cell-surface membranes which bind to the surface antigens of APC’s.
T helper cells produce interleukins (type of cytokine - cell signalling molecule).
These interleukins stimulate the activity of B cells; increasing antibody production, stimulates production of other T cells, and attracts and stimulates macrophages to ingest pathogens with antigen-antibody complexes.

Question 15

T Killer Cells

Answer 15

T Killer cells destroy the pathogen carrying the antigen.
T Killer cells produce perforin; a chemical which kills the pathogen by making holes in its cell membrane making it freely permeable.

Question 16

T Memory Cells

Answer 16

T Memory Cells are part of the immunological memory and live for a long time.
Upon meeting an antigen a second time, T Memory cells divide rapidly to form a huge number of clones of T Killer cells to destroy the pathogen quickly.

Question 17

T Regulator Cells

Answer 17

T Regulator Cells suppress the immune system, acting to control and regulate it.
T Regulator Cells stop the immune response once a pathogen has been eliminated, and make sure the body recognises self antigens and does not set up an autoimmune response. Interleukins are important in this control.

Question 18

Plasma Cells

Answer 18

Type of B Lymphocyte
Plasma cells produce antibodies to a particular antigen and release them.
An active plasma cell only lives a few days but produces 2000 antibodies per second.

Question 19

B effector cells

Answer 19

Type of B Lymphocyte

B Effector cells divide to form the plasma cell clones

Question 20

B Memory Cells

Answer 20

Type of B lymphocyte
B Memory cells live a long time, providing immunological memory.
B Memory cells are programmed to remember a specific antigen and enable the body to make a rapid response when a pathogen carrying that antigen is encountered again.

Question 21

Cell-Mediated Immunity

Answer 21

IMMUNE RESPONSE THAT DOESN’T INVOLVE ANTIBODIES
In Cell-Mediated Immunity, T Lymphocytes respond to cells of the organism that have been changed is some way, e.g. by virus infection. The cell-mediated response is important against viruses and early cancers.

Question 22

Cel-Mediated Immunity; process

Answer 22

1) in the non-specific defence system, macrophages engulf and digest pathogens in phagocytosis. Macrophages process the antigens from surface of pathogen, forming APC’s.
2) Receptors on some of the T Helper cells fit the antigens. These T Helper cells become activated and produce interleukins, stimulating more T Cells to divide rapidly by mitosis - form clones of identical activated T Helper cells that all carry the right antigen to bind to a particular pathogen.
3) the cloned T cells may:
•Develop into T memory cells, which give rapid response if this pathogen invade again.
•Produce interleukins, that stimulate phagocytosis.
•Produce interleukins, that stimulate B Cells to divide.
•Stimulate development of a clone of T Killer cells that are specific to the presented antigen, and then destroy infected cells.

Question 23

What is humoral immunity?

Answer 23

B Lymphocytes respond to antigens on pathogens by binding of their complimentary antibodies.
B memory cells are made so that if body encounters same pathogen again, antibodies can be quickly produced to wipe it out before symptoms occur.

Question 24

Stages of the Humoral Immunity response/process:

Answer 24

1) Activated T Helper Cells bind to the B Cell APC ; Clonal Selection (point at which the B cell with the correct antibody for the antigen is selected)
2) interleukins produced by the activated T Helper cells activate the B cells
3) the activated B cells divide by mitosis to give clones of plasma and B memory cells - This is Clonal Expansion.
4) Cloned Plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to the antigens and disable them, or act as opsonins or agglutinins = Primary Immune Response.
5) Some cloned B cells develop in B Memory cells. If the body is infected by same pathogen again, yeh memory cells dive rapidly to for plasma cell clones - these produce the right antibody and destroy the pathogens rapidly before it causes symptoms of the disease = Secondary Immune Response

Question 25

Define Autoimmune disease

Answer 25

Immune system stops recognising ‘self’ cells and starts to attack healthy body tissue.
•immunosuppressant drugs that stop the immune system working can be used as a treatment, however leaves the individual at high risk of communicable diseases.

Question 26

Natural Active Immunity

Answer 26

Body encounters pathogen activating immune system, and antibodies are formed to destroy the pathogen.
T & B memory cells are produced so the body can immediately recognise and destroy the pathogen before becoming it casues symptoms if encountered again.

Question 27

Natural Passive Immunity

Answer 27

colostrum and breast-milk is very high in antibodies and the infant’s gut allows these to pass into the bloodstream, giving the baby antibody protection against disease.

Question 28

Artificial Active Immunity

Answer 28

Immune system is stimulated to make antibodies to a vaccine/safe form of antigen which is injected into the bloodstream (vaccination).
The primary immune response is triggered by the foreign antiges and actively produces antibodies.

Question 29

Artificial Passive Immunity

Answer 29

Antibodies are injected to prevent development of disease. Does NOT provide long-term immunity.
Gives tempoary immunity