[Maximum number: 2]

The sinoatrial node (SAN) and the atrioventricular node (AVN) have an important role in the control of the cardiac cycle. The timing of atrial and ventricular systole and diastole must be controlled so that blood passes through the heart efficiently.

(a)

Impulses sent out by the SAN pass to the AVN, where there is a short delay.

With reference to Fig. 1.1, explain why it is important for the control of the cardiac cycle that there is a short delay at the AVN after impulses have been sent out by the SAN.

[ 2 ]

[Maximum number: 5]

Fig. 2.1 shows a diagram of a section through a human heart.

Fig. 2.1

(a)

Cardiac muscle is described as myogenic as it naturally contracts and relaxes. With reference to the structures and tissues within the heart, describe how the cardiac cycle is initiated and coordinated.

[ 5 ]

[Maximum number: 4]

(a)

Describe the function of each of the following structures in the human heart:

[ 4 ]

(i)

sinoatrial node (SAN)

[ 2 ]

(ii)

atrioventricular node (AVN)

[ 2 ]

(a)

Explain the roles of the sinoatrial node (SAN), atrioventricular node (AVN) and the Purkyne tissue during one heart beat.

[ 5 ]

(a)

Describe the roles of the sinoatrial node (SAN) and the atrioventricular node (AVN) in the initiation and control of the cardiac cycle.

[ 4 ]

(b)

The Purkyne fibres pass down the septum and extend to the cardiac muscle at the base (apex) of the heart.

Explain why it is important that the Purkyne fibres extend to the base of the heart.

[ 2 ]

[Maximum number: 1]

Three areas involved in the control of heart action are listed.
1 atrioventricular node
2 Purkyne tissue
3 sinoatrial node

In which order are they involved?

$1 \rightarrow 2 \rightarrow 3$

$1 \rightarrow 3 \rightarrow 2$

$3 \rightarrow 1 \rightarrow 2$

$3 \rightarrow 2 \rightarrow 1$

The diagram shows the internal structure of the mammalian heart.
Which letter identifies the location of the atrioventricular node?

[Maximum number: 1]

The statements list some of the events in the cardiac cycle. They are not in the correct order.
Which statement describes the fifth of these events to occur in the cardiac cycle?
1 The impulse travels through Purkyne tissue.
2 A wave of excitation sweeps across the atria.
3 The atrioventricular node delays the impulse for a fraction of a second.
4 The sinoatrial node contracts.
5 The wave of excitation sweeps upwards from the base of the ventricles.
6 The ventricles contract.
7 The atria contract.

(a)

The sinoatrial node (SAN) and the atrioventricular node (AVN) are two regions of the heart. Explain the role of the SAN and the role of the AVN in the cardiac cycle.

[ 3 ]