3.4.4 - The Heart

Question 1

Name the chamber of the heart that produces the greatest pressure

Answer 1

Left ventricle

Question 2

State whether each of the following statements are true or false

a- The left and right ventricles contract together
b- Veins have pocket valves
c- Semilunar valves occur between the atria and ventricles
d- If a person’s cardiac output is 4.9dm3min-1 and their heart rate is 70 beats per minute, then their stroke volume is 0.7 DM3

Answer 2

a- T
b- T
c- F Semi lunar valves are in the aorta and pulmonary artery
d- F its 0.07 4.9/70

Question 3

In each case state what is being described

a- On contraction it forces blood into the ventricles
b- The relaxation phase of the heart
c-structures that prevent the flow of blood from the aorta into the left ventricle

Answer 3

a- muscular walls of Atria
b- diastole
c- Semilunar valves

Question 4

After a period of training, the heart rate is often decreased when at rest although the cardiac output is unchanged suggest a reason for this

Answer 4

Training builds up the muscles of the heart and so the stroke volume increases / more blood is pumped at each beat. This means that, if the cardiac output is the same, the heart rate/ number of beats per minute decreases

Question 5

Explain how their cardiac output could stay the same even when their resting heart
rate had decreased.

Answer 5

1. Cardiac output = stroke volume × heart rate
2. Accept CO = SV × HR
3. (So) stroke volume increases / increased size or volume of ventricles.
4. Neutral: more blood leaves heart
5. If the term stroke volume is not used, it must be defined

Question 6

The rise and fall in blood pressure in the aorta is greater than in the small
arteries.Suggest why. (3)

Answer 6

(Aorta)
1. (is) close / directly linked to the heart / ventricle / pressure is higher / is
very high;
2. (Aorta has) elastic tissue;
Accept elasticity
Ignore reference to muscle
3. (Aorta has) stretch / recoil.
Q Reject: contracts / relaxes / pumps
Accept: for mp 2 and mp 3, converse for small arteries if
qualified by little / less

Question 7

High blood pressure leads to an accumulation of tissue fluid. Explain how (3)

Answer 7

1. High blood pressure = high hydrostatic pressure;
2. Increases outward pressure from (arterial) end of capillary / reduces
   inward pressure at (venule) end of capillary;
3. (So) more tissue fluid formed / less tissue fluid is reabsorbed.
   Allow lymph system not able to drain tissues fast enough

Question 8

Explain the difference in the thickeness between the pulmonary artery and the pulmonary vein (1 m)

Answer 8

Pulmoary atery thicker as Arteries have a thick wall, whereas veins have thin walls. Arteries carry blood away from the heart and veins carry blood to the heart. … Pulmonary artery, though it carries deoxygenated blood, it has thick walls to support the high pressure with which blood is sent away from the heart.

Question 9

o explain how the pressure in the dog’s ventricle is

related to the thickness of the ventricle wall.

Answer 9

1. Thickness of wall increases because ventricle (wall) contracts;
   Must be idea that increase in thickness is linked to
   contraction
   Accept muscle for ventricle and systole for muscle
   contraction
2. Contraction causes the increase in pressure;
   Accept thickening of wall

Question 10

Some babies are born with a hole between the right and the left ventricles.
These babies are unable to get enough oxygen to their tissues.
Suggest why.

Answer 10

1. Blood flows from left ventricle to right
ventricle/ mixing of oxygenated and
deoxygenated blood;
2. Lower volume of (oxygenated) blood
leaves left ventricle/flows into aorta/C
OR
Lower pressure in blood leaving left
ventricle/flowing into aorta/C
OR
Less oxygen in blood leaving left
ventricle/aorta/C;

Question 11

Give 4 ways in which the structure of ariteries is differnt from veins (4)

Answer 11

thicker muscle
more elastic
no valves
narrower lumen

Question 12

The aorta has many elastic fibres. An arterole has many muslce fibres in its wall. Explain the importance of elastic fibres in the wall? (3)

Answer 12

• Stretches and Expands under high pressure when ventricle contracts
• Recoils under low pressure when ventricle relaxes
• smooths blood flow and maintains blood pressure reduces pressure surges

Question 13

An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow to capillaries (2)

Answer 13

Muscle contracts

Arteriole narrows (vasocontriction)

Question 14

A capillary has a thin wall. This leads to rapid exchange of substances between the blood and tissue fluid. Explain why (1)

Answer 14

Short diffusion pathway

Question 15

Describe and explain how the wall of an artery is adapted to withstand and maintain high hydrostatic pressure (5)

Answer 15

• To withstand pressure wall is thick (collagen)
• Thick elastic tissue
• To cause recoil
• Thick smooth muscle
• narrows constricts lumen

Question 16

Give 4 differences between the structure of a vein and the structure of a capillary (4)

Answer 16

• Veins are more than 1 layer capillaries have 1 layer
• Capillaries dont have smooth muscle or elastic fibres
• Veins have valves
• Veins have wider lumen

Question 17

The pressure fluctuates as the blood flows along the aorta.

Suggest why it is important that the pressure changes as blood flow from the aorta to the capillaries (2)

Answer 17

Capillary wall is thin reduce change of tissue fluid build up

high pressure would burst it

Question 18

Arteries and capillaries are blood vessel adapted for specific roles in the circulatory system.
Give 3 differences between the structure of an artery and a capillary (3)

Answer 18

Arteries have a wider lumen
Capillaries are 1 cell thick an has 1 layer arteries have more and are thicker
Arteries have elastic fibres and muscle fibres