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17 Cards in this Set
- Front
- Back
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The nodal/conducting cells have very strong contractions.
T of F |
F
They have very weak contractions b/c there are few contractile elements |
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The nodal/conducting cells have a self- __________ factor.
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Excitability (meaning they can spontaneously generate action potentials)
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Why is the SA node the "pacemaker" of the heart?
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It is the first area to spontaneously depolarize, producing an action potential
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What do chronotropic effects do?
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Produce changes in heart rate
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A __________ chronotropic effect decreases heart rate by decreasing the firing rate of the SA node
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Negative
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What are dromotropic effects?
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Changes in conduction velocity (primarily AV node)
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In first degree AV node block the PR interval does not exceed .2 seconds.
T or F |
F
does exceed .20 seconds (normal range is .12-.20) |
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Describe second degree AV node.
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Occurs when AV node is damaged so severely that only one out of every two, three, four atrial electrical waves can pass through to the ventricles.
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What is the result of third degree (complete) AV block?
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Bradycardia
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Name the two types of myocardial cells.
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Contractile and nodal/conducting
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Contractile cells are similar to...
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Skeletal cells
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Nodal/conducting cells are similar to...
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Nerve cells
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How do contractile cells differ from skeletal cells?
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They have one nucleus and have tons of mitochondria
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What are contractile cells extremely efficient at?
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Extracting oxygen (at about 80%)
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Gap junctions allow myocardial cells to do what?
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Can conduct action potentials from cell to cell without the need for nerves
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What is contractility (inotropism)?
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The intrinsic ability of the cardiac muscle to develop force at a given muscle length.
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What are the three factors that increase contractility (positive inotropism)?
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Increased heart rate
Sympathetic stimulation Cardiac glycosides |
