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17 Cards in this Set

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