Term
| Basic properties of cardiac cells |
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Definition
1. Automaticity
2. Conductivity
3. Contractility
4. Rhythmicity |
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Term
| Resting potential of ventricular muscle |
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Definition
| -90 mV, lowest excitability of all cardiac cells, contract last. |
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Term
| Resting potential of SA node cells |
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Definition
-60 mV.
Most excitability of cardiac cells, pacemaker cell. |
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Term
| AV Node resting potential |
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Definition
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Term
| Atrial muscle resting potential |
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Definition
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Term
| Hypoxic affects on resting potential |
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Definition
| Hypoxia raises the resting potential in cells, can raise ventricular muscle TRP from -90mV to -75mV, can be the source of premature beats in heart. |
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Term
| Differences in action potential across ventricular wall |
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Definition
| Ventricular wall consists of subendocardial and subepicardial muscle fibers. The Purkinje fibers travel closer to the subendocardium, so initiates depolarization in those cells first. Subepicardium repolarizes faster, so action potential curve of subepicardium fits within the action potential curve of the subendocardium. Summation of waves creates the QRS complex (beginning of AP) and T wave (end of AP). |
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Term
| Sequence of depolarization in ventricles |
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Definition
1. Depolarization starts in the upper part of ventricular septum. Travels down septum.
2. Depolarization wave then goes into myocardium of right ventricle.
3. This is followed by a depolarization predominance in the left ventricle that overshadows right ventricle depolarization on an EKG. Direction of impulses point predominately to the left, a deviation in the direction of impulse caused by right ventricle hypertrophy can be seen on the EKG. |
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Term
| Repolarization of ventricles. |
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Definition
1. Have SD segment (period of electrical silence) before T wave repolarization.
2. T wave repolarization proceeds slowly from AV node. |
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Term
| Automaticity rates of cardiac cells |
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Definition
SA node: 60-100 bpm, fastest rate, pacemaker cell
AV junction: 40-60 bpm
Ventricle: <40 bpm
Ionic conditions determine bpm |
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Term
| Absolute Refractory Period (ARP) |
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Definition
| Period in AP where generation of another AP is impossible. |
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Term
| Relative Refractory Period |
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Definition
| Part of AP where it is more difficult to generate another AP. If impulse is large, than another AP is generated earlier than normal. |
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Term
| Reentry mechanism in Paroxysmal Atrial Tachycardia (PAT) |
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Definition
| Block in normal conduction slows down repolarization wave. Causes impulses to cycle in repeatedly near AV node back to ventricles (reentry phenomenon). |
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