ch 12.4: excitation-contraction processes in cardiac muscle

cardiovascular system

cardiac muscle contractile cells

myocardial cells

where are myocardial cells located

myocardium

by what are myocardial cells bound together

intercalated discs

what do intercalated discs contain

gap junctions and desmosomes

conducting cells, autorhythmic cells, pacemaker cells

nodal cells

specialized to depolarize throughout the heart

nodal cells

what prolongs depolarization in myocardial cells

L-type Ca²⁺ channels

what is the initial depolarization on myocardial cells caused by

opening of voltage-gated Na⁺ channels

what causes repolarization in myocardial cells

closing of L-type Ca²⁺ channels and opening of K⁺ channels

what are the two causes of increased sarcoplasmic Ca²⁺

influx from L-type Ca²⁺ channels and release from SR

generates a pacemaker potential due to unique channel behavior, which in turn triggers depolarization

SA node

ecg part showing atrial depolarization

p wave

ecg part showing ventricular depolarization and atrial repolarization

qrs complex

ecg part showing ventricular repolarization

t wave