Week 5: Pharmacology of Cardiac Disease (Chapter 14)
Cardiac System
Sinoatrial node (SAN): Main pacemaker (100 bpm) of the heart by spontaneous electrical
activity (called pacemaker potential/current or “funny current”). Action potential of SAN
cells is relatively small, with slowly rising depolarisation due to Ca 2+ influx.
o
Atrial and ventricular myocyte action potentials: fast initial rise with prolonged period of
depolarisation (plateau phase due to Ca2+ influx).
o
o Ventricular AP: no “funny current” – no spontaneous rhythmicity, the Ca 2+ plateau is
refractory – enables synchronicity and limits random excitations.
Atrioventricular node (AVN): Responsible for delay between atrial and ventricular systole
(0.1s). Also acts as a filter of random excitations (ectopy) from the atrium to the ventricles.
Therefore, ventricular HR is not as high as atrial HR.
,
ECG:
o
Cardiac System
Sinoatrial node (SAN): Main pacemaker (100 bpm) of the heart by spontaneous electrical
activity (called pacemaker potential/current or “funny current”). Action potential of SAN
cells is relatively small, with slowly rising depolarisation due to Ca 2+ influx.
o
Atrial and ventricular myocyte action potentials: fast initial rise with prolonged period of
depolarisation (plateau phase due to Ca2+ influx).
o
o Ventricular AP: no “funny current” – no spontaneous rhythmicity, the Ca 2+ plateau is
refractory – enables synchronicity and limits random excitations.
Atrioventricular node (AVN): Responsible for delay between atrial and ventricular systole
(0.1s). Also acts as a filter of random excitations (ectopy) from the atrium to the ventricles.
Therefore, ventricular HR is not as high as atrial HR.
,
ECG:
o
