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22 Cards in this Set
- Front
- Back
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SA node
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automatic rhythm generator for the heart |
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Vagus nerve |
causes SA node to slow down by acetycholine |
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Sympathetic Stimulation
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pours adrenaline into heart which accelerates heart |
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automaticity
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cells of heart can generate spontaneous action potentials, each section has different speeds |
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nervous system of heart
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not made of nerves, specialized muscle cells that conduct current |
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If SA node fails
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then Av node, then purkinje fibers |
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SA node automacity changes
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determined by changesin CA++, NA+, and K+ conductances |
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Maximal Heart Rate
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220 BPM - age in years |
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Nitric Oxide
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causes vasorelaxation |
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Coronaries
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supply the muscle and conducting system |
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Cardiac Muscle Delay
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because of CA++ channels that keep the cell depolarized |
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SA node spread
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spreads radially from the SA node across the atria to the AV node and down the bundle branches to the ventricular muscle and Purkinje network. |
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Resting Cell
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Positive ions on the outer surface and negative ions inside equal an electrically balanced or polarized cell |
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Depolarized cell |
negative ions on the outer surface and positive ions inside |
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Repolarization of cell |
positive ions return to the outside |
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Muscle fiber electrical axtivation processes
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current directon toward electrode |
produces a positive upward deflection |
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current flows away from the electrode |
produces a negative downward deflection |
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current flows toward electrode placed at a distance |
produce a positive but smaller amplitude than in the first one |
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Electrical current action potential phases
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electrical current arriving at the cell causes positively charged ions to cross the cell membrane, which causes depolarization, followed by repolarization, which generates an action potential |
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Stage 4 depolarization
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B- blockers inhibit or decrease spontaneous phase 4 depolarization caused by catecholamines, especially that caused by ischemia |
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