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16 Cards in this Set
- Front
- Back
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Systole |
Contraction and emptying of the atria and then the ventricles
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Atrial Systole |
- tricuspid and mitral valves open - pulmonic valve and aortic valve are closed - atria contract, pushing blood into the ventricles -atrial kick contributes about 30% to cardiac output |
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Ventricular Systole |
- blood flows into the ventricles forcing the pulmonic and aortic valves to open - ventricles contract - blood goes to the lungs from the right and to the body from the left (ventricular ejection) - |
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Diastole |
Relaxation of atria and ventricles - atria fill with blood - once atrial pressures exceeds ventricular pressure the mitral valve and tricuspid valve will open, and blood flows passively into the ventricles |
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SNS |
- sympathetic branch (adrenergic) - heart’s accelerator - Epinephrine and norepinephrine increase heart rate and improve contractility - Beta-blockers (beta-adrenergic blockers) block sympathetic activity, decrease heart rate and contractility |
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PNS |
- parasympathetic branch (cholinergic) - heart’s brakes - vagus nerve and the neurotransmitter acetylcholine decrease heart rate - Atropine (anticholinergic) blocks acetylcholine and the vagus nerve’s effect on the heart, increases heart rate |
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Automaticity |
refers to the cells ability to spontaneously initiate an impulse. Pacemaker cells of the heart have this ability |
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Excitability |
occurs from a shift of ions across the cell membrane; indicates how well a cell will respond to an electrical stimulus |
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Conductivity |
cells ability to transmit an electrical impulse to another cardiac cell |
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Contractility |
refers to how well the cell contracts after receiving the impulse |
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Polarized Cells |
- cells at rest (no electrical activity) - resting potential - inside of the cell is electrically negative while the outside is positive |
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Depolarization-Repolarization Cycle |
Phase zero: cell receives impulse or stimulus and is depolarized, initiates a heartbeat. Sodium moves rapidly into the cell and Ca moves slowly into the cell. The heart contracts. Phase 1: early repolarization; sodium channels close (sodium can no longer move intracellular). Phase 2: period of slower repolarization; calcium continues to move into the cell and potassium continues to move out of the cell. Phase 3: rapid repolarization as calcium channels close, potassium continues to flow out, and by the end of phase 3 the sodium/potassium pump begins restoring potassium in the cell and sodium outside the cell. Phase 4: resting phase of the action potential. By the end of phase 4, cardiac cells are ready for another stimulus and depolarization. EKG represents only the electrical activity of the heart.
Phases 1, 2 & early Phase 3: cardiac cell is in absolute refractory period, no impulse, no matter how strong, can excite the cell.
Last Portion of Phase 3: a very strong stimulus can depolarized the cell → relative refractory period
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Action Potential Curve |
shows the electrical changes within a myocardial cell |
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Repolarization |
resting phase of the heart |
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Sinoatrial Node (SA Node) |
- pacemaker (60 - 100 BPM) - located in the R upper atrium - normal cardiac impulse begins in the sinoatrial node - impulse travels through both atria via internodal pathways |
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Atrioventricular Node (AV Node) |
- electrical impulse is delayed slightly at the AV node (40 - 60 BPM) - travels down the atrioventricular bundle (Bundle of His) - separates into R & L bundle branch - impulse reaches Purkinje fibers |
