6. Defence Against Infectious Disease Flashcards Preview

Biology: Y12 EOY > 6. Defence Against Infectious Disease > Flashcards

Flashcards in 6. Defence Against Infectious Disease Deck (20)
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1
Q

What is a pathogen?

A

an organism or virus that causes disease

2
Q

What are the body’s primary defence against pathogens? How do they work?

A
  • skin and mucous

- by forming a barrier preventing entry

3
Q

How does the skin act as a barrier preventing pathogens from entering the body?

A
  • outer layers of skin are tough and form a physical barrier
  • sebaceous glands in the skin secrete lactic acid and fatty acids, which make the surface of the skin acidic. this prevents the growth of most pathogenic bacteria
4
Q

How do mucous membranes act as a barrier preventing pathogens from entering the body? Where are they found? How

A
  • mucous membranes are soft areas of skin that are kept moist with mucus
  • Although they do not form a strong physical barrier, many bacteria are killed by lysosome, an enzyme in mucus
  • mucous membranes are found in the nose, trachea, vagina and urethra
  • in the trachea pathogens get caught in the sticky mucus; cilia then push the mucus and bacteria up and out of the trachea
5
Q

What other defences, apart from skin and mucus, does the body have?

A

white blood cells:

  • phagocytes
  • lymphocytes
6
Q

How do phagocytes ‘kill’ pathogens?

A
  • phagocytes ingest pathogens by endocytosis

- pathogens then killed and digested inside the cell by enzymes from lysosomes

7
Q

Where do phagocytes act?

A
  • in the blood
  • can also squeeze out through the walls of blood capillaries and move through tissues to sites of infection. They then ingest the pathogens causing the infection
8
Q

What do large numbers of phagocytes at an infection form?

A

A SUPER MEGA ULTRA PHAGOCYTE???

pus.

9
Q

What sort of immunity do phagocytes give us? Why?

A
  • non-specific immunity to diseases, because a phagocyte does not distinguish between pathogens - it ingests any pathogen if stimulated to do so
10
Q

Draw and label a phagocyte ingesting some pathogens.

A

-

11
Q

What happens when the skin is cut and blood escapes from the blood vessels?

A

a semi-solid blood clot is formed from liquid blood to seal up the cut and prevent entry of pathogens

12
Q

What ‘thing’ has a critical role in blood clotting? What are they?

A
  • platelets

- small cell fragments that circulate with red and white blood cells in blood plasma

13
Q

How does the clotting process begin? What happens as a result of this?

A
  • with the release of clotting factors either from damaged tissue cells (epithelial cells) or from platelets
  • a cascade of reactions in which the product of each reaction is the catalyst of the next reaction
14
Q

What does the cascading system help to ensure?

A
  • that clotting only happens when it is needed

- also makes it a very rapid process

15
Q

What happens in the last reaction in blood clotting? What is the result of this?

A
  • fibrinogen, a soluble plasma protein, is altered by the removal of sections of peptide that have many negative charges
  • this allows the remaining polypeptide to bind to others, forming long protein fibres called fibrin (insoluble).
  • fibrin forms a mesh of fibres across wounds.
  • blood cells are caught in the mesh and soon form a semi-solid clot. If exposed to air, the clot tries to form a protective svab, which remains until the wound has healed.
16
Q

Draw a diagram showing the reactions initiated by clotting factors.

A
  1. reactions initiated by clotting factors released by platelets or damaged tissue cells
  2. prothrombin activator (prothrombin (inactive) –> thrombin (active))
  3. fibrinogin (soluble) –> fibrin (insoluble)
17
Q

What could happen if deposits of plaque in coronary arteries rupture? What is this called?

A
  • blood clots form (coronary thrombosis), which may completely block the artery
  • consequences = an area of cardiac muscle receives no oxygen and so stops beating in a coordinated way
  • called: a heart attack
18
Q

What is fibrillation?

A

uncoordinated contraction of cardiac muscle

basically a heart attack

19
Q

Can the heart recover from fibrillation?

A
  • yes, sometimes it starts beating again

- but severe heart attacks can be fatal as contractions of the heart stop completely

20
Q

Sketch and label a diagram of a healthy artery. Sketch and label a diagram of a plaque lined artery. (p76)

A

-