Transport in Man

Question 1

Why is a transport system required for complex organisms?

Answer 1

• High metabolism requires more nutrients to enter and more metabolic waste to exit the body efficiently
• Direct exchange is not possible as most cells are not in direct contact with external environment
• Small surface area:volume ratio –> slow diffusion rate

Question 2

What is the advantage of having a

(a) closed circulatory system?
(b) double circulatory system?

Answer 2

(a) Blood is delivered at a higher pressure, allowing faster delivery of nutrients and removal of waste (than opened system)
(b) Blood enters lungs at a lower pressure to allow for more efficient gaseous exchange. Blood is pumped to the rest of the body at a higher pressure.

Question 3

What are the adaptions of red blood cell?

Answer 3

• Biconcave shape –> increased flow rate and increased surface area to volume ratio for diffusion of O2.
• Lack nucleus and organelles so more haemoglobin is packed
• Flexible and deformable membrane allows it to squeeze through capillaries more easily

Question 4

Describe phagocytes and lymphocytes.

Answer 4

Phagocytes:

• Granular cytoplasm
• Lobed nucleus
• Engulfs and ingests foreign particles, bacteria, dead cells, cell debris by phagocytosis

Lymphocytes:
-Large rounded nucleus, small amount of non-granular cytoplasm

T-cells:

• Directly destroy infected or cancerous cells
• Gives off signals for B-cells to produce antibodies

B-cells:

• produce antibodies that bind to antigen on the surface of bacteria and viruses, causing them to clump together to make it easier for phagocytes to engulf them
• Toxins produced by bacteria are also neutralised by antibodies

Question 5

What are adaptations of arteries?

Answer 5

• Muscular:
• regulate blood flow by vasodilation and vasoconstriction, changing the diameter of the lumen
• thick wall –> withstand high blood pressure

Elastic:

• stretches to withstand high blood pressure
• recoils to maintain high blood pressure between pump cycles

-narrow lumen: maintain high blood pressure

Question 6

What are adaptations of veins?

Answer 6

Thin wall: large/wide lumen –> large volume of blood can flow without resistance
Valves: prevent backflow of blood to ensure unidirectional blood flow back to heart

Question 7

What are adaptations of capillaries?

Answer 7

• Partially permeable, allowing only certain substances to pass through e.g. glucose, amino acids, urea
• Wall is one-cell, short diffusion distance, faster diffusion rate
• Highly branched network:
• large surface area:
  
  • large amount of materials exchanged
  • slow flow rate, more time to exchange materials

Question 8

Describe the cardiac conduction system

Answer 8

1. Sinoatrial node generates electrical impulse that spread across the atria causing them to contract
2. The impulse then travels to the atrioventricular node where there is a delay of 0.1s
   - prevents atrial and ventricular muscles from contracting at the same time to avoid inefficient filling and backflow of blood
   - Allows blood from atria to completely fill ventricles
3. Impulse continues through the bundle of his, bundle branches and purkinje fibres.
4. On receiving the stimulation, ventricles start to contract from the base of the heart upwards.
5. There is a short delay before SA node generates the next wave of action potential.