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Lab Exercise 31 - Conduction System of the Heart

functional syncytium

entire myocardium acts as single unit do to cardiac muscles being connected by gap junctions

intrinsic conduction system/nodal system

consists of specialized non-contractile myocardial tissue, ensures heart contracts (depolarizes) orderly, beats as coordinated unit

Sinoatrial Node (SA Node)

pacemaker of the heart, signals contraction of atria

Atrioventricular Node (AV Node)

signals contraction of ventricles

purkinje fibers (conduction myofibers)

spread signal up into ventricles = contraction

electrocardiogram (ECG)

graphic recording of electrical changes during cardiac cycle; records time & voltage only

p wave

atrial depolarization, 1st small bump on graph

QRS complex

ventricalular depolarization, spiked area on graph (atrial repolarization)

t wave

ventricular repolarization, 2nd slightly bigger bump after the qrs complex


heart rate over 100 bpm


heart rate below 60 bpm, athletes is ok, can train to increase stroke volume w/ lower heart rate


rapid, uncoordinated contractions out of rhythm (prolonged tachycardia can progress to this)

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