Topic 6

Question 1

Describe the mechanism that control the heart beat

Answer 1

• the contraction of the heart tissue is myogenic
• within the wall of right atrium are specialized plexus of nerves called sinoatrial node
• SA node sends waves of impulse to atria and stimulus to the AV node
• sympathetic nerves speed up heart rate
• parasympathetic nerves slow down heart rate

Question 2

Arteries

Answer 2

• carry blood at high pressure (80-120 mm Hg)
• a narrower lumen surround by a thick wall made of two layers
• middle layer is made of muscle and elastin to maintain high pressure
• outer layer consists of collagen to prevent artery rupturing due to the high-pressure blood flow

Question 3

Veins

Answer 3

• carry blood at low pressure (<10 mm Hg)
• wide lumen
• thin walls that contains more collagen and less elastin than arteries
• contain valves

Question 4

Capillaries

Answer 4

• carry blood at relatively low pressure ( ca. 15 mm Hg)
• small diameter leads to exchange
• no muscle

Question 5

Describe a pathogen

Answer 5

• a disease-causing micro-organism, virus, or prion

Question 6

Explain why antibiotics are effective against bacteria and not viruses

Answer 6

• Antibiotics are substances that kill the growth of bacteria by targeting the metabolic pathways of prokaryotes.
• Specific prokaryotes features include 70S ribosomes, key enzymes and the bacterial cell wall.
• Eukaryotes does not have these features and therefore antibiotics can kill bacterial cells without harming any human cells and not viruses either.
• Viruses does not carry out metabolic reactions but infect a host cell instead and take over their machinery

Question 7

Skin

Answer 7

• protects external structures

- made of predominantly dead cells

Question 8

Mucuos

Answer 8

• protects internal structures

- thin region containing living surface cells that release fluids to wash away pathogens

Question 9

Distinguish between antigen and antibody

Answer 9

Antigen: a substance that is recognized as a foreign and that can evoke an immune response

Antibody: a protein produced by B cells and plasma cells, in response to an antigen

Question 10

Explain antibody production

Answer 10

1. Antigen binds to the antibody on the plasma membrane of a B cell.
2. Antigen is taken up by exocytosis and presented on the MHC protein.
3. Macrophage engulf the antigen by endocytosis (phagocytosis) and express it on the MHC protein on the plasma membrane.
4. T cell binds to the macrophage that presents the antigen on the MHC protein and T cell is now activated T helper cell.
5. Activated T helper cell binds to the B cell that expresses the antigen on MHC protein on the plasma membrane, and B cell becomes activated.
6. Activated B cell starts dividing rapidly and make clones of plasma cells and some memory cells. The memory cells survive in the bloodstream for years, while plasma cells are short-lived.
7. Each plasma cell packed with rER starts mass-producing antibody molecules