Cardiac Conduction System

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Cardiac Conduction System
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Cardiac Conduction System

• Intrinsic Conduction System
• Autonomic
• Cell types
• Specialized cells
• Contractile cells

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Intrinsic Conduction System

• Sinoatrial (SA) node
• Pacemaker
• Location
• Cells
• Function

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Intrinsic Conduction System

• Atrioventricular (AV) Node
• Location
• Myocytes
• Function

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Intrinsic Conduction System

• AV Bundle (Bundle of His)
• Right and Left Bundle Branches
• Function
• Purkinje Fibers
• Cell shape
• Location
• Left ventricle
• Function
• Atria
• Electrical excitation
• Connective tissue

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Intrinsic Conduction System
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Electrocardiography

• Amplifies the signals of the cardiac conduction
  system, and produces and electrocardiogram
• Shows three principal deflection waves
• P wave
• Indicates depolarization of the atria immediately
  before atrial contraction
• QRS wave
• Indicated ventricular depolarization.
• Atrial repolarization happens simultaneously
• QRS wave represents simultaneous activation of
  left and right ventricles
• T wave
• Indicates ventricular repolarization, immediately
  before diastole

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ECG
Normal Sinus Rhythm
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ECG

• How do the contractions of the heart and the
  waves of an ECG correlate?
• McGraw-Hill - Essential Study Partner

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ECG

• What an ECG does and doesnt show
• Record of voltage and time
• Records electrical events occurring in large
  amounts of muscle tissue
• We can only infer that muscle contraction follows
  excitement of the muscle
• We can only infer nodal tissue activity
• Changes in time intervals can indicate
  abnormalities
• Myocardial infarcts
• Problems with conducting system

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ECG

• Normal vs abnormal
• P-Q interval
• 0.16 - 0.18 seconds
• Longer interval may indicate AV heart
  block/damaged AV node
• QRS interval
• 0.08 seconds
• Prolonged interval may indicate right or left
  branch block
• One ventricle contracting later than the other.
• Q-T interval
• 0.31 0.41 seconds with a heart rate of 70
  beats/minute
• As the rate increases, the interval becomes
  shorter
• As the rate decreases the interval becomes longer

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Heart Rate

• Abnormalities
• Tachycardia
• Heart rate over 100 beats/minute
• Bradycardia
• Heart rate under 60 beats/minute
• In athletes, indicates increased efficiency of
  cardiac function increased stroke volume
• Fibrillation
• Prolonged tachycardia
• Uncoordinated heart contractions

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