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ECG
Anatomy & Physiology
| Term | Definition |
|---|---|
| Automaticity | Ability of pacemaker cells to INITIATE an electric stimulus spontaneously WITHOUT external stimulus |
| Excitability is the ability of cardiac muscle cells to ___ to an ___ electric stimulus | Respond; outside |
| Conductivity is the ability of cardiac cells to ___ an electric impulse and propagate the impulse to __ | Receive; next cell |
| Contractility is the ability of cardiac cells to shorten ___ | In respond to electric stimulus |
| In diastole the __ of the cell is electrically more ___ than __ of the cell | Inside; negative; outside |
| In resting state, there are more __ ions than __ inside the cell | K+, Na+ |
| Depolarization is the ___ of the cell membrane | Electrical excitation |
| Repolarization is the ___ of cell membrane to its ___ ___ | Return; resting states |
| In repolarization, the channels for __ open and it flows out, taking the __ charge with it | K+, positive |
| At end of ___, the Na-K pumps in cell membrane move potassium in and sodium out of cells | Repolarization |
| ___ is the primary pacemaker of the heart | SA node |
| SA Node cells depolarize automatically at rate of ___ | 60-100 |
| AV Node can function as the ___ of the heart | Backup pacemaker |
| AV Node automatically depolarize at rate of ___ | 40-60 |
| AV Node ___ the conduction of the impulse from atria to ventricles from dangerously fast rate | Slows |
| Bundle of HIS is | Short bundle of fibers at bottom of AV node leading to BBs |
| Bundle Branches | Carry impulse into R and L ventricles. |
| Purkinje fibers act as the ___ pacemaker, automatically depolarizing at rate of | Final backup; 20-40 |
| P wave represnts | Atrial depolarization as impulse travels through atria |
| PR interval represents | Atrial depolarization + AV conduction time |
| Normal PR interval is | 0.12-0.20 |
| QRS represents | Ventricular depolarization and intraventricular conduction time |
| Q wave represents | 1st negative deflection from baseline |
| R wave represents | 1st POSITIVE deflection from baseline (ALWAYS upright) |
| S wave represents | Negative deflection following R |
| Normal width of QRS | 0.06-0.10 |
| T wave repesents | Ventricular repolarization |