4.4 Heart And Circulation

Question 1

Compare artery, vein and capillaries

Answer 1

Artery have:
Thick walls(one cell thick)
Long elastic walls
Narrow lumen - high pressure blood away from heart
Contains a valve - backflow

Veins
Long elastic walls
Low pressure towards heart

Capillaries
Thin layer for fast gas exchange
One cell thick
Fast gas exchange
Branched
Low pressure

Question 2

Name the structures of the heart

Answer 2

Vena cava, aorta, pulmonary vein , vena cava, pulmonary artery , atrioventricular valves(bicuspid/tricuspid), semi lunar valves, septum, cardiac muscle, arteries.

Question 3

Advantage of double circulatory system

Answer 3

-Concentration gradient is maintained as oxygen and -deoxygenated blood do not mix
Blood pressure to the blood pressure to the body tissues is higher
- blood pressure to the lungs is lower avoiding damage to the capillaries in the lungs increasing gas exchange
- organisms can develop larger bodies

Question 4

What is blood made off?

Answer 4

Plasma
Red blood cells
White blood cells
Platelets

Question 5

Explain the hearts ability to initiate contraction(myogenic)

Answer 5

Impulse starts at SA node(informal node) and a wave of excitement is spreading through the atria causes both atria to contract the cardiac impulses reach the AV node(atrioventricular node) delaying the impulse to allow atria to finish contraction spreading to the bundle of his splitting into 2 branches - purkinje fibres causing both ventricles to contract. The ventricles then relax and the cycle repeats.

Question 6

Why is blood clotting useful

Answer 6

To prevent blood loss
Forms a barrier to prevent entry of pathogens causing diseases
Repairs tissues and cells
Platelets attach to exposed collagen fibres releasing a protein that triggers the conversion of in active proteins into active enzymes(thrombin) catalysing the synthesis of fibrin forming a network of fibres forming a blood clot.

Question 7

What does disassociation curves illustrate

Answer 7

Changes in haemoglobin saturation as partial pressure changes. High partial pressure means haemoglobin has high affinity for oxygen and is highly saturated vice versa. At low partial pressures oxygen disassociates causing oxygen to be released to respiring tissues. Disassociating curve has a sigmoid shape because saturation affects affinity.

Question 8

Explain the Bohr effect

Answer 8

High levels of carbon dioxide causes the affinity for oxygen to decrease causing more oxygen to be released for respiring tissues shifting to the right meaning small animals have a high affinity active organism have a lower affinity so oxygen is released more for respiration.

Question 9

Haemoglobin vs myoglobin

Answer 9

Haemoglobin
Has a quaternary structure
4 haem groups
Myoglobin
Single polypeptide
1 haem group

Myoglobin has higher affinity and is easily saturated because of its structure