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Module 6 - Human Physiology > 6.3 - Defence against Infectious Disease > Flashcards

6.3 - Defence against Infectious Disease Flashcards

1
Q

Provide 2 examples of the first line of defence.

A
  • the SKIN: protects external structures

- MUCOUS MEMBRANES: protects internal structures

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2
Q

Provide 3 ways in which mucous membranes assist in the defence against disease.

A
  • sticky, which traps pathogens
  • can contain lysozymes which can cause cell lysis
  • can be ciliated (hairy) which aids in the removal of pathogens
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3
Q

Define pathogen.

A

A disease causing organism.

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4
Q

Draw a flowchart to describe how clotting occurs after blood vessel damage.

A
  • the broken vessel releases CLOTTING FACTORS
  • these clotting factors cause PLATELETS to become STICKY, which forms a plug around the wound
  • these clotting factors also cause VASOCONSTRICTION, reducing blood flow through the damaged region
  • these clotting factors convert PROTHROMBIN into THROMBIN, the active form
  • thrombin converts FIBRINOGEN into FIBRIN
  • a network of fibrin forms a plug around the wound
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5
Q

What can lead to a clot forming in coronary vessels?

A

Cholesterol deposition, which can lead to blood vessel damage.

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6
Q

What are the consequences of clotting in coronary artery vessels?

A
  • reduces the diameter or lumen of the vessel
  • it becomes less elastic
  • can lead to blockage and blood cannot pass through
  • that part of the heart tissue dies!
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7
Q

What are platelets?

A

Tiny blood cells that help in clotting.

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8
Q

What is the second line of defence?

A

A NON-SPECIFIC process which involves phagocytosis, inflammation and fever.

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9
Q

Is the first line of defence specific?

A

NO.

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10
Q

Is the second line of defence specific?

A

NO!

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11
Q

What are the roles of phagocytes in the defence against infectious disease?

A
  • phagocytes circulate in the blood and move into body tissues due to the release of histamines
  • these cells engulf pathogens
  • pathogenic fragments form a vesicle within the cell, and it fuses to the lysosome
  • this allows the phagocyte to digest the pathogen
  • parts of the pathogen may be presented on the surface of the phagocyte.. VERY important for the third line of defence…….
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12
Q

What is the role of histamine?

A
  • when tissue becomes damaged after the first line of defence has been breached, histamine is released.
  • this is a chemical messenger which causes vasodilation
  • blood vessels dilate, allowing phagocytes to move into the infected area
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13
Q

What is a phagocyte?

A

A type of cell capable of engulfing pathogens or other cells.

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14
Q

Is phagocytosis a specific process?

A

NO.

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15
Q

Is the third line of defence a specific process?

A

Yes!

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16
Q

The first and second line of defence is innate, whereas the third line of defence is ____________?

A

ADAPTIVE.

17
Q

What is an antigen?

A

A substance that the body recognises as foreign.

18
Q

What is an antibody?

A

An immunological protein produced by B LYMPHOCYTES that is specific for a certain antigen.

19
Q

What is a lymphocyte?

A

A type of white blood cell which is involved in the third line of defence.

20
Q

What are the two types of lymphocytes?

A

B and T lymphocytes.

21
Q

Explain how the third line of defence works.

A
  • PHAGOCYTES (from the second line of defence) engulf pathogens and present the antigen on its surface
  • these antigen-presenting cells migrate to lymph nodes
  • here, HELPER T-CELLS are activated
  • these helper T cells activate specific B-CELLS
  • activated B cells divide and differentiate into PLASMA B-CELLS
  • these plasma B cells produce specific ANTIBODIES
  • antibodies target the specific antigen and help to destroy the pathogen
  • a portion of B and T cells will remain as memory cells to provide long lasting immunity against the specific antigen
22
Q

What is a lymph node?

A

Specialised small organs which form the lymphatic system, helps to filter substances travelling through the lymph and contains lymphocytes.

23
Q

What is an antibiotic?

A

A chemical which kills or inhibits the growth of bacteria.

24
Q

List two ways in which antibiotics work.

A
  • prevent bacterial cell wall formation (they cannot live without this)
  • target the 70S ribosome (cells need to make proteins or else they die!!)
25
Q

Why don’t antibiotics work on viruses?

A

Antibiotics work by targeting and blocking metabolic pathways. Viruses are not alive and do not possess metabolic pathways.

26
Q

How does antibiotic resistance arise?

A
  • within a population of bacteria, there is a proportion which possess antibiotic resistance genes
  • when an antibiotic is used, the non-resistant cells die whereas the ones with the resistance genes survive
  • these cells are able to pass on its genetic material and hence resistance to subsequent generations
  • since bacteria reproduce rapidly, this leads to a population of resistant bacteria and antibiotic resistance
27
Q

What is one example of antibiotic resistance?

A

MRSA

methicillin resistant staphylococcus aureus

28
Q

Outline Florey and Chain’s experiments to test penicillin on bacterial infections in mice.

A
  • eight mice were injected with a pathogenic bacteria
  • four mice were then injected with penicillin, an antibiotic
  • the other four mice (control group) were left untreated
  • the control group died, demonstrating the antibiotic potential of penicillin
29
Q

What is HIV and what does the virus target?

A

Human Immunodeficiency Virus - infects helper T-cells

30
Q

What can HIV lead to?

A

AIDS

31
Q

What are the effects of HIV?

A
  • the virus infects helper T-cells
  • following infection, the cells can remain inactive for years. During this period though, the infected cells can replicate.
  • eventually the virus becomes active again and spreads, infecting more cells
  • reduction in T cells leads to a decreased production in antibodies
  • ultimately the body becomes more immune to infections and disease
32
Q

How is HIV transmitted?

A
  • sexual contact
  • mother to child during pregnancy
  • through needles
  • blood transfusion

Module 6 - Human Physiology (6 decks)

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