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13 Cards in this Set
- Front
- Back
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Time from atria to ventricles
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200ms
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Pacemaking ability of Purkinje Fibers
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Slow
Usually overridden by SA node |
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Cardiac action potential
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Na channels open
Membrane depolarizes Ca channels open Ca causes internal Ca to be released |
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Ca channels (role, function)
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Voltage-gated channel is activated by depolarization
Very slow deactivation Maintains depolarization (maintains Na channels inactivation) |
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Differences between SA node and ventricle (reasons)
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SA node has slower upstroke (not as many Na channels)
SA node doesn't have plateau phase (not as many Na channels) Quicker re-depolarization (funny channels) |
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Electrical syncitium
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All of the atrial cells of connected via gap junctions
No gap junctions between atrial and ventricular cells |
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Cardiac T Tubules
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Bring in extracellular Ca
Stimulates release of intracellular Ca |
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Cardiac muscle inactivation
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T tubule channels are inactivated by Ca
Sarcoplasmic membrane takes up Ca |
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Negative chronotropy
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Slowing down of heart by parasympathetic innervation (via ACh)
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Parasympathetic mechanism of heart rate
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Opens an inward rectifying K channel
Counteracts depolarizing effects of the pacemaker channels |
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Sympathetic effect on heart rate (mechanism)
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Releases catecholamines
Activate pacemaker cells, inward rectifying K channels and Ca channels Increases conductance and the increased pacemaker increases heart rate |
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Inotropic
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Strength of contraction
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Catecholamines inotropic effect
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Causes a larger and faster internal Ca concentration, which causes stronger contractions
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