DEPOLARIZATION - ANSMovement of ions (Na+, Ca+, K+) across cell membrane causing
inside of cell to become more positive, electrical conduction results in contraction. Na+ channels
open. Positive inside, negative outside.
REPOLARIZATION - ANSmovement of ions across cell membrane where inside of cell is
restored to its negative charge. Sodium channels close. Potassium channels open. Active
transport by sodium-potassium pump
WHAT OCCUR FIRST? ELECTRICAL CONDUCTION, OR MECHANICAL CONTRACTION? -
ANSELECTRICAL CONDUCTION
P WAVE - ANSATRIAL DEPOLARIZATION
QRS - ANSVENTRICAL DEPOLARIZATION
T WAVE - ANSventricular repolarization
REFRACTORY PERIOD - ANSthe period of resistance to stimulation, cardiac cells unable to
respond to stimulus
relative refractory period - ANScardiac cells have repolarized enough to respond to strong
stimulus
automaticity - ANSAbility of pacemaker cells to spontaneously initiate an electrical impulse, SA
node, AV junction, and Purkinje fibers
excitability - ANSability to respond to stimuli
conductivity - ANSAbility to receive an electrical stimulus and conduct that impulse to adjacent
cells - all cardiac cells possess this.
contraction - ANSCardiac cells shorten, causing muscular contraction in response to an
electrical stimulus
SA node - ANSSino-atrial node; the pace-maker of the heart; where the impulse conduction of
the heart usually starts; located in the top of the right atrium. 60-100 bpm
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