Book notes: Chapter 13 - Electrical activity of the heart

From Iusmphysiology

Contents 1 Key Concepts 2 The ionic basis of cardiac electrical activity: the cardiac membrane potential 2.1 The cardiac membrane potential depends on transmembrane movements of sodium, potassium and calcium 2.2 The opening and closeing of cation channels cause the ventricular action potential 2.2.1 Depolarizing early in the action potential: selective opening of sodium channels 2.2.2 Late depolarization (plateau): selective opening of calcium channels and closing of potassium channels 2.2.3 Repolarization: selective opening of potassium channels 2.2.4 Resing membrane potential: open potassium channels 2.3 The opening of Na and Ca and the closing of K channels causes the pacemaker potential of the SA and AV nodes 2.3.1 The refractory period is caused by a delay in the reactivation of Na channels 2.3.2 Neurotransmitters and other ligands can influence membrane ion conductance 3 The initiation and propagation of cardiac electrical activity 3.1 Excitation starts in the SA node because SA cells reach threshold first 3.2 The action potential is propagated by local currents created during depolarization 3.3 Excitation usually spreads from the SA node to atrial muscle to the AV node to the purkinje system to ventricular muscle 3.3.1 Slow conduction through the AV node 3.3.2 Rapid conduction through the ventricles 4 The electrocardiogram 4.1 The ECG records the dipoles produced by the electrical activity of the heart 4.1.1 Measurement of the voltage associated with a dipole 4.1.2 Changes in dipole magnitude and direction 4.2 Portions of the ECG are associated with electrical activity in specific cardiac regions 4.2.1 The p wave and atrial depolarization 4.2.2 The PR interval and atrioventricular conduction 4.2.3 The QRS complex and ventricular depolarization 4.2.4 The ST segment and Phase 2 of the ventricular action potential 4.2.5 The T wave and ventricular repolarization 4.2.6 The QT interval 4.3 ECG leads give the voltages measured between different sites on the body 4.4 The ECG provides information about cardiac dipoles as vectors 4.5 The mean QRS electrical axis is determined from the limb leads 4.6 The ECG permits the detection and diagnosis of irregularities in heart rate and rhythm 4.7 The ECG provides three types of information about the ventricular myocardium 4.7.1 The pattern of ventricular excitation 4.7.2 Changes in the mass of electrically active ventricular myocardium 4.7.3 Abnormal dipoles resulting from ventricular myocardial injury

[edit] Key Concepts

[edit] The ionic basis of cardiac electrical activity: the cardiac membrane potential

[edit] The cardiac membrane potential depends on transmembrane movements of sodium, potassium and calcium

[edit] The opening and closeing of cation channels cause the ventricular action potential

[edit] Depolarizing early in the action potential: selective opening of sodium channels

[edit] Late depolarization (plateau): selective opening of calcium channels and closing of potassium channels

[edit] Repolarization: selective opening of potassium channels

[edit] Resing membrane potential: open potassium channels

[edit] The opening of Na and Ca and the closing of K channels causes the pacemaker potential of the SA and AV nodes

[edit] The refractory period is caused by a delay in the reactivation of Na channels

[edit] Neurotransmitters and other ligands can influence membrane ion conductance

[edit] The initiation and propagation of cardiac electrical activity

[edit] Excitation starts in the SA node because SA cells reach threshold first

[edit] The action potential is propagated by local currents created during depolarization

[edit] Excitation usually spreads from the SA node to atrial muscle to the AV node to the purkinje system to ventricular muscle

[edit] Slow conduction through the AV node

[edit] Rapid conduction through the ventricles

[edit] The electrocardiogram

[edit] The ECG records the dipoles produced by the electrical activity of the heart

[edit] Measurement of the voltage associated with a dipole

[edit] Changes in dipole magnitude and direction

[edit] Portions of the ECG are associated with electrical activity in specific cardiac regions

[edit] The p wave and atrial depolarization

[edit] The PR interval and atrioventricular conduction

[edit] The QRS complex and ventricular depolarization

[edit] The ST segment and Phase 2 of the ventricular action potential

[edit] The T wave and ventricular repolarization

[edit] The QT interval

[edit] ECG leads give the voltages measured between different sites on the body

[edit] The ECG provides information about cardiac dipoles as vectors

[edit] The mean QRS electrical axis is determined from the limb leads

[edit] The ECG permits the detection and diagnosis of irregularities in heart rate and rhythm

[edit] The ECG provides three types of information about the ventricular myocardium

[edit] The pattern of ventricular excitation

[edit] Changes in the mass of electrically active ventricular myocardium

[edit] Abnormal dipoles resulting from ventricular myocardial injury