Lab 2. The Intrinsic Cardiac Conduction System. 1/23/2016 MDufilho 1

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1 Lab 2 he Intrinsic Cardiac Conduction System 1/23/2016 MDufilho 1

2 Figure Intrinsic cardiac conduction system and action potential succession during one heartbeat. Superior vena cava ight atrium 1 he sinoatrial (SA) node (pacemaker) generates impulses. acemaker potential Internodal pathway 2 he impulses pause (0.1 s) at the atrioventricular (AV) node. 3 he atrioventricular (AV) bundle connects the atria to the ventricles. Left atrium Subendocardial conducting network (urkinje fibers) SA node Atrial muscle AV node 4 he bundle branches conduct the impulses through the interventricular septum. Interventricular septum acemaker potential lateau Ventricular muscle 5 he subendocardial conducting network depolarizes the contractile cells of both ventricles. Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Milliseconds Comparison of action potential shape at various locations 1/23/2016 MDufilho 2

3 Video Conducting System Of he Heart 1/23/2016 MDufilho 3

Membrane potential (mv) Figure 18.12 acemaker and action potentials of pacemaker cells in the heart.

4 Membrane potential (mv) Figure acemaker and action potentials of pacemaker cells in the heart Action potential 3 ime (ms) 2 hreshold 3 acemaker potential 1 1 acemaker potential his 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. 2 Depolarization he action potential begins when the pacemaker potential reaches threshold. Depolarization is due to Ca 2+ influx through Ca 2+ channels. 3 epolarization is due to Ca 2+ channels inactivating and K + channels opening. his allows K + efflux, which brings the membrane potential back to its most negative voltage. 1/23/2016 MDufilho 4

SA node Depolarization epolarization 1 Atrial depolarization, initiated by the SA node, causes the wave. AV node 4 Ventricular depolarization is complete.

5 SA node Depolarization epolarization 1 Atrial depolarization, initiated by the SA node, causes the wave. AV node 4 Ventricular depolarization is complete. 2 With atrial depolarization complete, the impulse is delayed at the AV node. 5 Ventricular repolarization begins at apex, causing the wave. 3 Ventricular depolarization begins at apex, causing the QS complex. Atrial repolarization occurs. 6 Ventricular repolarization is complete. 1/23/2016 MDufilho 5

6 Sinoatrial node QS complex Atrial depolarization Ventricular depolarization Ventricular repolarization Atrioventricular node -Q Interval S- Segment Q- Interval 1/23/2016 MDufilho 6

Figure 18.18 Normal and abnormal ECG tracings.

7 Figure Normal and abnormal ECG tracings. Infant undergoing an electrocardiogram (ECG) ECG Cardiac Arrest Normal sinus rhythm Normal ECG trace (sinus rhythm) Junctional rhythm he SA node is nonfunctional. As a result: waves are absent. he AV node paces the heart at beats per minute. Second-degree heart block he AV node fails to conduct some SA node impulses. As a result, there are more waves than QS waves. In this tracing, there are usually two waves for each QS wave. Ventricular fibrillation Electrical activity is disorganized. Action potentials occur randomly throughout the ventricles. esults in chaotic, grossly abnormal ECG deflections. Seen in acute heart attack and after an electrical shock. MDufilho

Figure 18.15 Intrinsic cardiac conduction system and action potential succession during one heartbeat. Superior vena cava ight atrium 1 he sinoatrial (SA) node (pacemaker) generates impulses.

8 Figure Intrinsic cardiac conduction system and action potential succession during one heartbeat. Superior vena cava ight atrium 1 he sinoatrial (SA) node (pacemaker) generates impulses. acemaker potential Internodal pathway 2 he impulses pause (0.1 s) at the atrioventricular (AV) node. 3 he atrioventricular (AV) bundle connects the atria to the ventricles. Left atrium Subendocardial conducting network (urkinje fibers) SA node Atrial muscle AV node 4 he bundle branches conduct the impulses through the interventricular septum. Interventricular septum acemaker potential lateau Ventricular muscle 5 he subendocardial conducting network depolarizes the contractile cells of both ventricles. Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Milliseconds Comparison of action potential shape at various locations 1/23/2016 MDufilho 8

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10 acemaker Inplantation acemaker 1/23/2016 MDufilho 10

11 Surgery for acemaker Getting a acemaker 1/23/2016 MDufilho 11

THE CARDIOVASCULAR SYSTEM. Heart 2

THE CARDIOVASCULAR SYSTEM. Heart 2 THE CARDIOVASCULAR SYSTEM Heart 2 PROPERTIES OF CARDIAC MUSCLE Cardiac muscle Striated Short Wide Branched Interconnected Skeletal muscle Striated Long Narrow Cylindrical PROPERTIES OF CARDIAC MUSCLE Intercalated