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17 Cards in this Set
- Front
- Back
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What is conduction velocity?
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The rate at which an excitation impulse is able to spread throughout the cardiac tissue.
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What does conduction velocity depend on?
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The magnitude of the inward current due to the influx of ions during phase 0 of the cardiac action potential.
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Where is conduction velocity fastest?
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Purkinje system.
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Where is conduction velocity the slowest?
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AV node
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What does the difference in conduction time between the AV node and the Purkinje system allow the heart to do?
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It allows for ventricular filling.
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What can happen if conduction velocity through the AV node is increased?
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Ventricular filling can become compromised.
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What is a dromotropic effect?
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Anything that produces a change in conduction velocity, especially in the AV node.
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What type of dromotropic effect does the sympathetic nervous system produce?
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Positive dromotropic effect.
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How does the sympathetic nervous system produce its dromotropic effect?
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Increases conduction velocity through the AV node and decreases the PR interval by increasing the inward Ca+ current.
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What is the receptor and neurotransmitter for the sympathetic effect?
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Beta-1 receptor, norepinephrine (NE) is the neurotransmitter.
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What type of dromotropic effect does the parasympathetic nervous system produce?
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Negative dromotropic effect
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How does the parasympathetic system produce its dromotropic effect?
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Decreases conduction velocity through the AV node and increases the PR interval by decreasing the inward Ca+ current and increasing the outward K+ current.
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What is the receptor and neurotransmitter for the parasympathetic effect?
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Muscarinic receptor, acetylcholine(ACh) is the neurotransmitter.
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What is excitability?
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The ability of the cardiac muscle cells to initiate an action potential after being depolarized by an inward current.
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What is ARP?
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Absolute refractory period. The time during which no action potential can be initiated regardless of the magnitude of the inward current.
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What is ERP?
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Effective refractory period.
The time during which no conducted action potential can be produced. |
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What is RRP?
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Relative refractory period.
The time during which an action potential can be initiated, but rerquires a larger inward current. |
