CVS2 - My name is Intercalated disc (aka: gap junction), Im...

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My name is Intercalated disc (aka: gap junction), I’m very sweet as I let ions travel from one cell to another very very quickly
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Cardiac Muscle Contraction Heart muscle: Is stimulated by nerves and is self-excitable (automaticity)
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Cardiac Muscle Contraction Heart muscle: Contracts as a unit (functional syncytium)
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Cardiac Muscle Contraction Heart muscle: Has a long (250 ms) absolute refractory period
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Cardiac Muscle Contraction Heart muscle: Has a long (250 ms) absolute refractory period
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Cardiac Muscle Contraction Heart muscle: Has a long (250 ms) absolute refractory period P Q R S T
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Cardiac Muscle Contraction Cardiac muscle contraction is similar to skeletal muscle contraction
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Heart Physiology: Intrinsic Conduction System Autorhythmic cells: Initiate action potentials -60 mV -40 mV T pacemaker potential action potential (~150 msec) 0 mV - 1 2 3 4
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Heart Physiology: Intrinsic Conduction System Autorhythmic cells: Have unstable resting potentials called pacemaker potentials -60 mV -40 mV T pacemaker potential action potential (~150 msec) 0 mV - 1 2 3 4
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Heart Physiology: Intrinsic Conduction System Autorhythmic cells: Use calcium influx (rather than sodium) for rising phase of the action potential
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Action potentials in pacemaker (autorhythm ic) cells -60 mV -40 mV T pacemaker potential action potential (~150 msec) 0 mV - Pacemaker cells in sinoatrial (SA) node drive heart rate Membrane potential of autorhythmic cells is never stable; starts ~ -60 mV and drifts upward at -60 mV, a monovalent cation channel, I f , is open at this potential, Na + influx depolarizes the cell toward threshold at threshold. Ca 2+ channels open, I f channels close and Ca 2+ influx dominates; further depolarizing the cell at peak of AP, Ca 2+ channels close and slow K channels have opened. K + efflux hyperpolarizes the cell at ~ -60 mV again, I f channels open, starting the depolarizing pacemaker potential again Rate of action potentials in the pacemaker cells is modulated by sympathetic and parasympathetic input sympathetic activity epinephrine norepinephrine Increase flow of ions through I f and Ca 2+ channels Speeds up pacemaker potential (heart rate) normal sympathetic faster depolarization more depolarized
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Heart Physiology: Sequence of Excitation Sinoatrial (SA) node generates impulses about 75 times/minute
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Heart Physiology: Sequence of Excitation Atrioventricular (AV) node delays the impulse approximately 0.1 second
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Heart Physiology: Sequence of Excitation Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)
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AV bundle splits into two pathways in the interventricular septum (bundle branches) Bundle branches carry the impulse toward the apex of the heart
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CVS2 - My name is Intercalated disc (aka: gap junction), Im...

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