3.1.2g) How heart action is initiated and coordinated

Question 1

Myogenic

Answer 1

Cardiac muscle can relax & contract without receiving signals from nerves
Patterns of contractions control the regular heartbeat

Question 2

Sino-atrial node (SAN)

Answer 2

In the wall of the right atrium
Acts as a pacemaker - sets the rhythm of the heartbeat by sending regular electrical waves over the atrial walls
Causes both atria to contract at the same time
The electrical waves are transferred to the AVN

Question 3

Atrio-ventricular node (AVN)

Answer 3

Responsible for passing the electrical waves onto the Bundle of HIS
Slight delay before AVN reacts - makes sure the ventricles contract after the atria have emptied

Question 4

Bundle of HIS

Answer 4

Group of muscle fibres responsible for conducting electrical waves to finer muscle fibres in the ventricle walls - purkinje fibres

Question 5

Purkinje fibres

Answer 5

Carries waves of electrical activity into the muscular of the ventricles - causing them to contract simultaneously (from bottom up)