Electrical Properties of the Heart

Cardiac Action Potential

sinoatrial (SA) node

atrioventricular (AV) node

Resting Membrane Voltage

inward rectifying K⁺ current – i_K1

fast-response action potentials

genesis of the upstroke (phase 0)

activate/inactivate

effective refractory period

relative refractory period

genesis of early repolarization (phase 1)

transient outward current (i_to)

genesis of the plateau (phase 2)

genesis of final repolarization (phase 3)

restoration of ionic concentrations (phase 4)

Na⁺,K⁺-ATPase

slow-response action potentials

Conduction in Cardiac Fibers

Cardiac Excitability

fast response

slow response

Effects of Cycle Length

Natural Excitation and the ECG

automaticity

rhythmicity

sinoatrial node

ionic basis of automaticity

overdrive suppression

atrial conduction

atrioventricular conduction

bundle of His

ventricular conduction

bundle branches

Purkinje fibers

reentry

triggered activity

early afterdepolarizations (EADs)

delayed afterdepolarizations (DADs)

Electrocardiography (ECGs)

scalar electrocardiography

P – QRS – T

standard limb leads

resultant cardiac vector

I – II – III

Einthoven’s triangle

augmented limb leads

aV_R – aV_L – aV_F

chest (V) leads

V₁–V₂: anteroseptal

V₃–V₄: anteroapical

V₅–V₆: anterolateral

Arrhythmias

altered sinoatrial rhythm

bradycardia

tachycardia

atrioventricular conduction blocks

first-degree

second-degree

third-degree

premature depolarizations

coupled extrasystoles

ectopic tachycardias

paroxysmal tachycardias

fibrillation

Links

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