Non-specific animal defences against pathogens 12.5

Question 1

How is the skin an example of a non-specific defence against pathogens

Answer 1

The skin covers the body and prevents the entry of pathogens. It has a skin flora of healthy microorganisms that outcompete pathogens for space on the body surface. The skin also produces sebum, an oily substance that inhibits the growth of pathogens

Question 2

How do mucus act as a non-specific defence againt pathogens

Answer 2

traps microorganisms
contains lysozymes to help destroy bacterial and fungal cell walls
also contains phagocytes to help remove pathogens

Question 3

How do tears, urine and stomach acid also act as a non-specific defence

Answer 3

Lysozymes in tears and urine, and the acid in stomach acid help to prevent pathogens getting into our bodies.

Question 4

How do expulsive relfexes act as non-specific defences

Answer 4

Coughs and sneezes eject pathogen-laden mucus from the gas exchange system, while vomiting and diarrhoea expel the contents of the gut along with any infective pathogens.

Question 5

what are some substances that are secreted when a platelet comes into contact with wall of damaged blood vessels

Answer 5

• Thromoboplastin, an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot ( or thrombus)
• Serotonin, which makes the smooth muscle in the walls of the blood vessels contract, so they narrow and reduce the supply of blood to the area

Question 6

Explain what happens to the abrasion site after the clot has formed

Answer 6

• clot dries out(forms scab, barrier against pathogens)
  ^first stage of wound repair
• Epidermal cells below scab start growing, sealing wound
• damaged blood vessels regrow.
• Collagen fibres deposited to give new tissue strength.
• Once epidermis is normal thickness, scab comes off and wound is healed.

Question 7

what is an inflammatory response

Answer 7

localised response resulting in inflammation at the site of a wound or infection

Question 8

What is inflammation

Answer 8

• vasodilation
• Increased vascular permeability
• Recruitment of immune cells

Question 9

What do mast cells release and when are they activated

Answer 9

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

Question 10

What do histamines and cytokines do

Answer 10

• Cytokines attract white blood cells (phagocytes) to the site. They dispose of pathogens by phagocytosis.
• histamines cause vasodilation causing localised increase in temp to prevent pathogens reproducing, also increase permeability of vessels to produce more tissue fluid (contains whiteblood cells)

Question 11

How does a fever work
how is it an example of a non-specific immune response

Answer 11

• pathogen enters body, cytokines stimulate hypothalamus to increase body temperature
• ^pathogens reproduce best at or below 37°C (normal body temp).
• The specific immune system works faster at higher temperatures.
• Its the same for all pathogens ( non-specific)

Question 12

What are the 2 types of phagocytes that are involved in non-specific defences

Answer 12

Neutrophils and macrophages

Question 13

what are the stages of phagocytosis

Answer 13

1) Pathogens produce chemicals that attract phagocytes
2)Phagocytes recognise non-human proteins on the pathogen. This is a response not to a specific type of pathogen, but simply a cell or organism that is non-self
3)The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
4) The phagosome combines with a lysosome to from a phagolysosome
5)Enzymes from the lysosome digest and destroy the pathogen

Question 14

How long does it take a neutrophil to destroy a bacterium

Answer 14

It usually takes a human neutrophil under 10 minutes to engulf and destroy a bacterium

Question 15

What does a macrophage do once it has digested a pathogen

Answer 15

combines pathogen antigens with proteins in cytoplasm to form major histocompability complex, which then presents antigens on cell membrane which stimulates other immune cells

Question 16

What can identifying the number of different lymphocytes tell us

Answer 16

Identifying the numbers of different types of lymphocytes in a blood smear indicates if a non-specific or specific immune response is taking place

Question 17

What is produced when a phagocyte has engulfed a pathogen

Answer 17

cytokines are produced

Question 18

What is the function of cytokines

Answer 18

• cytokines act as cell-signalling molecules, informing other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation.
• Cytokines can also increase body temperature and stimulate the specific immune system

Question 19

What are opsonins and what are there function

Answer 19

• Opsonins are chemicals that bind to pathogens and ‘tag’ them so they can be more easily recognised by phagocytes.
• Phagocytes have receptors on their cell membranes that bind to common opsonins, and the phagocytes then engulfs the pathogen. There are a number of different opsonins, but antibodies such as immunoglobulin G and immunoglobulin M have the strongest effect.