lab 2 the intrinsic cardiac conduction system 1/24/20101mickey dufilho
DESCRIPTION
Figure Pacemaker and action potentials of autorhythmic cells of the heart Pacemaker potential This slow depolarization is due to both opening of Na + channels and closing of K + channels. Notice that the membrane potential is never a flat line. Depolarization The action potential begins when the pacemaker potential reaches threshold. Depolarization is due to Ca 2+ influx through Ca 2+ channels. Repolarization is due to Ca 2+ channels inactivating and K + channels opening. This allows K + efflux, which brings the membrane potential back to its most negative voltage. Action potential Threshold Pacemaker potential /24/20103Mickey DufilhoTRANSCRIPT
Lab 2
The Intrinsic Cardiac Conduction System
1/24/2010 1Mickey Dufilho
Figure 18.14 Cardiac intrinsic conduction system and action
potential succession during one heartbeat.
Milliseconds(b) Comparison of action potential shape at various locations
(a) Anatomy of the intrinsic conduction system showing the sequence of electrical excitation
Pacemakerpotential
Pacemaker potential
Plateau
Internodal pathway
Superior vena cavaRight atrium
Left atrium
Purkinjefibers
Inter-ventricularseptum
SA node
Atrial muscle
AV node
Ventricularmuscle
1 The sinoatrial(SA) node(pacemaker)generates impulses.
2 The impulsespause (0.1 s) at theatrioventricular(AV) node.
Theatrioventricular(AV) bundleconnects the atriato the ventricles.
4 The bundle branches conduct the impulses through theinterventricular septum.
3
The Purkinje fibersdepolarize the contractilecells of both ventricles.
5
1/24/2010 2Mickey Dufilho
Figure 18.13 Pacemaker and action potentials of autorhythmic
cells of the heart.
1 2 3 Pacemaker potentialThis slow depolarization is due to both opening of Na+
channels and closing of K+
channels. Notice that the membrane potential is never a flat line.
Depolarization The action potential begins when the pacemaker potential reaches threshold. Depolarization is due to Ca2+
influx through Ca2+ channels.
Repolarization is due to Ca2+ channels inactivating and K+ channels opening. This allows K+ efflux, which brings the membrane potential back to its most negative voltage.
Actionpotential
Threshold
Pacemakerpotential
1 1
2 2
3
1/24/2010 3Mickey Dufilho
1 Atrial depolarization, initiatedby the SA node, causes theP wave.
P
R
T
QS
SA node
AV node
2
3
With atrial depolarizationcomplete, the impulse is delayed at the AV node.
Ventricular depolarizationbegins at apex, causing theQRS complex. Atrial repolarization occurs.
P
R
T
QS
P
R
T
QS
4
5
6
Ventricular depolarizationis complete.
Ventricular repolarizationbegins at apex, causing theT wave.
Ventricular repolarizationis complete.
P
R
T
QS
P
R
T
QS
P
R
T
QS
Depolarization Repolarization
1/24/2010 4Mickey Dufilho
Sinoatrialnode
Atrioventricularnode
Atrialdepolarization
QRS complex
Ventriculardepolarization
Ventricularrepolarization
P-QInterval
S-TSegment
Q-TInterval
1/24/2010 5Mickey Dufilho
Figure 18.181/24/2010 6Mickey Dufilho
Figure 18Cardiac intrinsic conduction system and action potential succession during one heartbeat.
Milliseconds(b) Comparison of action potential shape at various locations
(a) Anatomy of the intrinsic conduction system showing the sequence of electrical excitation
Pacemakerpotential
Pacemaker potential
Plateau
Internodal pathway
Superior vena cavaRight atrium
Left atrium
Purkinjefibers
Inter-ventricularseptum
SA node
Atrial muscle
AV node
Ventricularmuscle
1 The sinoatrial(SA) node(pacemaker)generates impulses.
2 The impulsespause (0.1 s) at theatrioventricular(AV) node.
Theatrioventricular(AV) bundleconnects the atriato the ventricles.
4 The bundle branches conduct the impulses through theinterventricular septum.
3
The Purkinje fibersdepolarize the contractilecells of both ventricles.
5
1/24/2010 7Mickey Dufilho
Pacemaker
http://www.youtube.com/watch?v=8Mz36HnMsYY 1/24/2010 8Mickey Dufilho