The Heart (pages 82 - 83)

Question 1

The Heart consists of TWO Muscular Pumps.

Look at diagrams 1 and 2 on page 82, it shows the internal and external structure of the heart.

What do the right side of the heart pump?
what do the left side of the heart pump?

Answer 1

The right side pumps deoxygenated blood to the lungs
the left side pumps oxygenated blood to the reso of the body.

Question 2

List the External Structure of the Heart?

Answer 2

see diagram 1 on page 82

Pulmonary artery
left atruim
pulmonary veins
left vensticle
superior vena cava
aorta
right atrium
conary artery
right ventricle
inferior vena cava.

Question 3

List the Internal Structure of the Heart?

Answer 3

see diagram 2 on page 82

aorta
pulmonary veins
left atrium
semi-lunar valve
atrioventricular valve
cords (valve tendons)
left ventricle
right ventrile
atrioventricular valve
semi-lunar valve
inferior vena carva
superior vena cava

Question 4

What do the atrivoventricular valves link to?

Answer 4

they link the artria to the ventricles.

Question 5

The artriventricular valves link the atria to the ventricles, and the semi-lunar valves link what?

Answer 5

the semi-lunar valves link ventricles to the pulmonary artery and aorta.

They all stop blood flowing the wrong way.

Question 6

How do the heart valves prevent blood flowing the wrong way?

Answer 6

1) the valves only open one way - whether they’re open or closed depends on the relative pressure of the heart chambers.

2) If there’s higher pressure behind a valve, it’s forced open.

3) If pressure is higher in front of the valve, it’s forced shut.

see diagram 3 and 4 of valve open and valve closed, on page 82.

Question 7

You need to carry out a heart Dissection (practical skills).

What equipment will you need?

Answer 7

You will need a pig or cow’s heart,
a dissecting tray
scalpel
an apron
lab gloves

Question 8

When carrying out a Heart Dissection (practical skills), what do you need to look at on the heart?

Answer 8

External Examination:
1) Look at the outside of the heart and try to identify the four main vessels attached to it.
2) Feel inside the vessels to help you - remember arteries are thick and rubbery, whereas veins are much thinner.
3) Identify the right and left atria, the right and left ventricles and the coronary arteries.
4) draw a sketch of the outside of the heart with labels.

Internal Examination:
1) Cut along the lines shown on the diagram (diagram 5 page 82), to look inside each ventricle.
2) Measure and record the thickness of the ventricle walls ad note any differences between them.
3) Cut open the atria and look inside them too. Note whether the atria walls are thicker or thinner than the ventricle walls.
4) Find the atriventricular valves, folled by the semi-lunar valves.
5) Look at the structure of the valves.
6) Draw a sketch to show the valves and the inside of the ventricles and atria.

Question 9

Why is the LEFT ventricle wall thicker and more muscular than the right?

Answer 9

to push blood all the way round the body.

Question 10

Why do the ventricles have thicker walls than the atria?

Answer 10

becasue they have to push blood OUT of the heart.

Question 11

What is the Cardiac Cycle?

Answer 11

it is an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continously circulating round the body.

The volumes of the atria and ventricles change as they contract and relax, altering the pressure in each chamber. This causes the valves to open and close, which directs the blood flow through the heart.

Question 12

The cardiac cycle can be simplified into three stages, what are the three stages?

Answer 12

1) Ventricles relax, atria contract
2) Ventricles contract, atria relax
3) Ventricles relax, atria relax

Question 13

Explain the first stage of the cardiac cycle

Ventricles relax, atria contract?

Answer 13

The ventricles are relaxed. The atria contract, which decreases their volume and increases their pressure. This pushes the blood into the ventricles through the atrioventricular valves. There’s a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contracting atria.

see diagram 1 on page 83

Question 14

Explain the second stage of the cardiac cycle:

Ventricles contract, atria relax?

Answer 14

The atria relax. The ventricles contract (decreasing their volume), increasing their pressure.
The pressure becomes higher in the ventricles than the atria, which forces the atrioventricular valves to shut to prevent back-flow.
The high pressure in the ventriclues opens the semi-lunar valves - blood is forced out into the pulmonary artery and aorta.

see diagram 2 on page 83.

Question 15

Explain the third stage of the cardiac cycle:
Ventricles relax, atria relax.

Answer 15

The ventricles and the atria both relax. The higher pressure in the pulmonary artery and aorta causes the semi-lunar valves to close, preventing back-flow.
The atria fill with blood (increasing their pressure) due to their higher pressure inthe vena cava and pulmonary vein.
As the ventricles continue to relax, their pressure falls below the pressure in the atria. This causes the atrioventricular valves to open and blood flows passively (without being pushed by atrial contraction) into the ventricles from the atria. The atria contract, and the whole process begins again.

see diagram 3 on page 83

Question 16

In the exam, you could be asked to calculate cardiac output. what is this?

Answer 16

This is the volume of blood pumped by the heart per minute (measured in cm³ (mim-¹)

It’s calculated using the formula: cardiac output = heart rate x stroke volume.

(heart rate is the number of beats per minute (bpm) and stroke volume is the volume of blood pumped during each heartbeat in cm³

Question 17

Which chamber of the heart receives blood from the lungs?

Answer 17

The left atrium receives blood from the lungs. This blood is rich in oxgen. The left ventricle pumps the blood from the left atrium out to the body, supplying all organs with oxygen-rich blood.

Question 18

The graph on page 83 shows the pressure changes in the left side of the heart during one heartbeat.

a) at which labelled point (A-H_ on the grap does:

i) the semi-lunar valve open?
ii) the artriventricular valve close?

Answer 18

a) i) D (1 mark) - the semi-lunar valve will only open if the pressure in the ventricle is higher than the pressure in the aorta (or pulmonary artery, if you’re looking at the right side of the heart).

ii) C (1 mark) The atrioventricular valve will be forced closed when the pressure in the ventricle becomes higher than the pressure in the atrium.

Question 19

b) on the diagram on page 83, sketch the graph that you would expect for the right bentricle (2 marks).

Answer 19

b) The graph should increase and decrease at the same times as the graph for the left side (because both ventricles contract together) 1 mark. The pressure should be lower than for the left side of the heart at all times [1 mark].

e.g. (see diagram on page 271, Q1b)
the left ventricle of the heart has thicker, more muscular walls than the right ventricle because it needs to contract powerfully to pump blood all the way round the body. The right side only needs to get blood to the lungs, which are nearby - this is why the pressure will always be lower in the right ventricle than the left.

apparently an adult heart is the size of two fists!!
if you listen to a heartbeat you’ll hear a ‘lub-dub’ sound. The first ‘lub’ sound is caused by the atrioventricular valves closing (state 2). The second ‘dub’ sound is caused by the semi-lunar valves closing (stage 3)