The document discusses the roles of the sinoatrial node, atrioventricular node, and Purkyne tissue in controlling the cardiac cycle. The sinoatrial node initiates electrical impulses that cause atrial contraction. The impulses then travel to the atrioventricular node and down the Purkyne tissue in the ventricles to trigger ventricular contraction. This coordinated process allows for the synchronized pumping of blood through the heart.

1. Control of the Cardiac Cycle
L/O To be able to identify key features of an ECG
To know the roles of the sinoatrial node, the
atrioventricular node and the Purkyne tissue
30 September 2013

2. Myogenic Heart
• http://www.youtube.com/watch?v=MojGH5P
XSTU

3. Synchronised pumping

4. Defibrillation

5. TV Lies

6. TV Lies

7. Control of the Cardiac Cycle
• Sinoatrial node (SAN) aka pacemaker – top of
right atrium
• Atrioventricular node (AVN) – top of the inter-
ventricular septum
• Purkyne Tissue – runs down the inter-
ventricular septum

8. SAN, AVN and Purkyne Tissue

9. SA node sends impulses
across walls of atria to
cause atrial systole
Impulse reaches
Base of ventricles to
Cause ventricular
systole
Blood leaves the heart
Impulse reaches AV
node and travels down
Interventricular septum
Impulses travels down
Purkinje fibres
in the Bundle of His
Blood enters the heart

10. SAN, AVN and Purkyne Tissue

11. Electrocardiograms

12. Electrocardiograms
P = atrial
excitation
QRS = excitation
of ventricles
T = diastole

14. Heart Attacks
• Heart muscle respires fatty acids
• Respiration of fat can only happen
aerobically, so the heart needs oxygen
• A blood clot in the coronary artery starves
part of the heart muscle of oxygen and those
cells die

16. Heart murmurs
• http://www.youtube.com/watch?v=XvtBpnV_l
OE