Unit 3 - Transport in Animals

Question 1

Name the type of blood vessel that controls blood flow to muscles and explain how these blood vessels change blood flow during exercise.

Answer 1

1. Arteriole;
2. (Circular/smooth) muscle relaxes;
3. Vasodilation increases blood flow

Question 2

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs.

Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.

Answer 2

1. Renal vein;
2. Vena cava to right atrium;
3. Right ventricle to pulmonary artery;

Question 3

Tissue fluid is formed from blood at the arteriole end of a capillary bed.

Explain how water from tissue fluid is returned to the circulatory system.

Answer 3

1. Large Plasma proteins remain in the blood;
2. Reduces water potential of blood;
3. Water moves (to blood) by osmosis;
4. Lymph returns to blood by lymph vessels;

Question 4

Explain how an arteriole can reduce the blood flow into capillaries.

Answer 4

1. Muscle contracts;
2. Constricts/narrows arteriole/lumen;

Question 5

The diagram below shows pressure and blood flow during the cardiac cycle in a dog.

Use information from the diagram above to calculate the heart rate of this dog.

Heart rate _______________ beats minute-1

Answer 5

167 (beats minute–1)

OR

164 (beats minute–1)

OR

171 (beats minute–1);

Question 6

Describe the advantage of the Bohr effect during intense exercise

Answer 6

1. Increases dissociation of oxygen;

Accept unloading/ release/reduced affinity for dissociation

2. For aerobic respiration at the tissues/muscles/cells

OR

Anaerobic respiration delayed at the tissues/muscles/cells

OR

Less lactate at the tissues/muscles/cells;

Question 7

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin.

Answer 7

1. Decreasing (blood) pH/increasing acidity;
2. Deceases haemoglobin’s affinity for O2;
3. Increases oxygen dissociation;

Question 8

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind. Explain why.

Answer 8

1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin;
2. Uncovers second / another binding site. Reject ref. to active site

Question 9

Explain the role of the heart in the formation of tissue fluid

Answer 9

1. Contraction of ventricle(s) produces high blood / hydrostatic pressure;
2. This forces water and small dissolved substances out of blood capillaries;
3. Do not accept contraction / pumping of the heart
4. Reject blood / plasma / tissue fluid forced out

Question 10

Explain four ways in which the structure of the aorta is related to its function

Answer 10

1. Elastic tissue to allow stretching /and recoiling smoothing out flow of blood and maintains pressure;
2. Elastic tissue stretches when ventricles contract and recoils when ventricle relaxes;
3. Smooth muscle for vasoconstriction;
4. Thick wall withstands pressure OR stop bursting;
5. Smooth endothelium reduces friction;
6. Aortic valve prevents backflow into heart.

Question 11

What is the function of the coronary arteries?

Answer 11

1. Carry oxygen / glucose; Accept: oxygenated blood
2. To heart muscle

Question 12

The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why.

Answer 12

1. Aorta is closer to the left ventricle where the pressure is higher
2. Aorta has elastic tissue;
3. Aorta can stretch at high pressure and recoil at low pressure, smoothing out blood flow

Q Reject: contracts / relaxes / pumps

Question 13

Describe how a heartbeat is initiated and coordinated

Answer 13

1. SAN sends wave of electrical activity / impulses (across atria) causing atrial contraction;

Accept excitation

2. Non-conducting tissue prevents impulses reaching the ventricles;
3. AVN delays impulse whilst blood leaves atria / ventricles fill;
4. AVN sends wave of electrical activity down Bundle of His;
5. Causing ventricles to contract from base up;

Question 14

Explain how oxygen is loaded, transported and unloaded in the blood.

Answer 14

1. At high p.O2 in the lungs,
2. Haemoglobin has a high affinity for oxygen
3. Oxygen associations forming oxyhaemoglobin;
4. At low p.O2; Haemoglobin has a lower affinity to oxygen;
5. Oxygen dissociates to respiring cells
6. Higher carbon dioxide concentration increases dissociation

Question 15

Describe and explain what is happening at A, B, C and D in the graph

Answer 15

A - Atrioventricular valves close – pressure inside the ventricle exceeds that of the atria

B - Semi-lunar valves open – pressure inside the ventricle exceeds that of the aorta

C - Semi-lunar valves close – pressure inside the aorta increases above that of the ventricle

D - Atrioventricular valves open – pressure inside the atria exceeds that of the ventricle

Question 16

Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.

Answer 16

1. permeable capillary wall
2. single endothelial cell thick reduces diffusion distance;
3. flattened endothelial cells, reduces diffusion distance;
4. fenestrations, allows large molecules through;
5. small diameter short diffusion distance;
6. narrow lumen, reduces flow rate giving more time for diffusion;
7. red blood cells in contact with wall gives short diffusion distance / more time for diffusion;

Question 17

Describe how tissue fluid is formed and reabsorbed

Answer 17

1. High hydrostatic pressure forces water and small molecules out of the capillary
2. Large plasma proteins remain in the blood lowering water potential
3. At the arterial end of the capillary, some water is reabsorbed by osmosis.
4. At he venus end, hydrostatic pressure is low
5. Lots of water moves back in by osmosis
6. Excess tissue fluid moves into the lymph vessel