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13 Cards in this Set
- Front
- Back
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the majority of the myocardium is made up of what type of cells?
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cardiac muscle cells.
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these cells have what 4 properties?
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excitability
contractibility extensibility elasticity |
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cardiac muscle has more _________ which make them resistant to fatigue. They can also extract a high percentage (70-80%) of ____ delivered to them by the blood
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mitochondria
O2 |
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What do desmosomes do?
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hold the heart fibers together--they are proteins which tightly link two adjoining cells.
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are the T-Tubule system and SR more or less extensive than skeletal muscle?
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less
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can contractions of cardiac muscle be graded? if so, how?
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yes. By increasing or decreasing the amount of sympathetic stimulation.
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increase of Epi and NE during exercise increases the force of cardiac contractions by increasing what?
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Ca^2+ entry.
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what does more Ca^2+ result in?
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more cross bridging and greater force of contraction.
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can parasympathetic control force of contraction?
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no. ONLY heart rate. (sympathetic can regulate rate and force)
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binding of NE to beta 1 receptors increases cell's permeability to ____, hypopolarizing the cell, increasing _____
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NA
HR |
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Binding of ____ to _________ receptors increases the cell's permeability to ____, hyperpolarizing the cell, decreasing frequency of impulses from SA node and _____
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Ach
muscarinic K+ HR |
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to effectively increase or decrease HR, what 2 things are needed to change?
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1- frequency of impulses from SA node
2- rate at which they pass through the AV node |
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the property of autorhythmicity is due to what?
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leaky ion channels that gradually hypopolarize the cell--resulting in an action potential.
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