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ECG ch2
Basic Electrophysiology
| Question | Answer |
|---|---|
| Specialized cells of the hearts electricial system also referred to as conducting or automatic cells | Packemaker cells |
| The ability of cardiac pacemaker cells to creat an electrical impulse without being stimulated from another source | Automaticity |
| Also called irritability referes to the ability of cardiac muscle cells to respond to an outside stimulus | Excitability |
| Refers to the ability of a cardiac cell to receive an elecrtrical impulse and and conduct ut to an adjoining cardiac cell | Conductivity |
| The ability of myocardial cells to shorten in response to an impulse which results in contraction | Contractility |
| The flow of electrical charge from one point to another | Current |
| The measurement of potential energy is | Voltage |
| Elements or compounds such as NA+ K+ CA+ and CL- that break into charged particles (ions) when melted or dissolved in water or other solvent | Electrolytes |
| Five phase cycle that reflects the difference in the concentration of these charged particles across the cell membrane at any given time | Action potential |
| When the inside of a cell is more negative then the outside | Polarized state |
| The voltage (difference in electrical charges) across the cell membrane | Membrane potential |
| The ability of a membrane channel to allow passage of electtolytes once it is open | Permeable |
| The movement of charged particles across a cell membrane causing the inside of the cell to become positive | Depolarization |
| The movement of charged particles across a cell membrane in which the inside of the cell is restored to its negative charge | Repolarazition |
| Phases 1,2,3 are referred to as | Electrical systole |
| Phase 4 is referred to as | Electrical diastole |
| This phase represents depolarazition. It is the rapid entry of NA+ into the cell | Phase 0 |
| During this phase the NA+ channels partially close, slowing the flow of NA+ into the cell. At the same time CL- enters and K+ leaves. Resulting in a decrease in the # of positive electrical charges within the cell | Phase 1 |
| The plateau phase. During this phase the CA++ slowley enters the cell as K+ continues to leave the cell slowley. It allows cardiac muscle to sustain an increased period of contraction | Phase 2 |
| This phase begins with the downslope of the action potential. The cell rapidly completes repolarazition as K+ quickly flows out of the cell which causes the inside to become more negative NA+ and CA+ channels close stopping the entry of the two. | Phase 3 |
| The resting membrane potential. During this phase an excess of NA+ is inside and K+ outside the cell. The NA+/K+ pump is activated to move NA+ outside and K+ back into the cell. The heart is polarized during this phase. | Phase 4 |
| The cell will not respond to further stimulation | Absolute refractory period aka Effective refractory period |
| Some cardiac cell have repolarized to their threshold potential and can be stimulated to respond to a stronger than normal stimulus. This corosponds with the T wave | Relative refractory period aka Vulnerable period |
| After the relative refractory period, a weaker then normal stimulus can cause cardiac cells to depolarize during this period. It extends from the end pf phase 3 to the beginning of phase 4 | Supernomral period |
| The soecialized electrical cells in the heart are arranged in a system of pathways called | Conduction system |
| When the AV junction is bypassed by an abnormal pathway the route is called | Accessory pathway |
| The leads that view the inferior surface of the heart | II, III, aVF |
| The leads that view the septal surface of the heart | V1 and V2 |
| The leads that view the anterior surface of the heart | V3 and V4 |
| The leads that view the lateral surface of the heart | I, aVL, V5, and V6 |
| It represents the spread of the impulse through the AV node, bundle of His, right and left bundle brnaches and the Purkinje fibers. It normally shortens as heart rate increases | PR interval |
| Normal rate for PR interval | .12-.20 secs |
| total ventricular activity- the time from ventricular depolarazition to repolarazition | QT Interval |
| Duration of the QT interval | under .38 secs |
| It represents activation of the AV node, the bundle of His, the bundle branches and the Purkinje fibers | PR segment |
| It represents the early part of repolarazition of the right and left ventricels | ST segment |
| Duration of the ST segment | .5 to +2mm |
| Represents atrial depolarazition | P wave |
| Duration of a P wave | no more then .11 secs |
| Represents the spread of the electricial impulse through the ventricles (ventricular depolarazition) | QRS Complex |
| Duration of a QRS complex | .10 secs or less |
| Represents ventricluar repolarazition | T wave |
| The primary pacemaker | SA Node |
| The PR interval is considered prolonged if it is more then | .20 secs |
| Which part of the conduction system receives an impulse from the bundle of His and relays it to the Purkinje fibers | Right and left bundle branches |
| On the ECG the time necessary fot the spread of an electrical impulse through the AV nodes, bundle of His, right and left bundle branches and the purkinje fibers is represented by the | PR segment |
| The portion of the ECG tracing used to determine the degree of ST segment displacement | TP or PR segment |
| Part of the conduction system that reseives an impulse from the SA node but delays relaying that impulse to the bundle of His, allowing time for the atria to empty their contents into the venticles before the onset of ventricular contraction | AV Node |
| Five large boxes each consisting 5 small boxes represents ? on ECG paper | 1 second |
| When using a 12 lead ECG this surface of the heart is not directly viewed | Right ventricle and posterios surface of the left ventricle |
| The appearence of coved ( frowny face) ST segment elevation is called | Acute injury pattern |
| A line between waveforms is called | Segment |
| The spread of an impulse through tissue already stimulated by that same impulse | Reentry |
| The cells of the heart that contain contractile filaments are called | Myocardial cells |
| Distortion of an ECG tracing by electrical activity that is noncardiac in origin is called | Artifact |
| A waveform and a segment | Interval |
| The relative refractory period is also called | Vulnerable |
| An ECG machine is a sophisticated ? | Voltmeter |
| This condition causes ST segment elevation in all or virtually all leads | Pericarditis |
| An important electrolye that affects cardiac function | Potassium |
| The difference in electrical charges across the cell membrane | Membrane potential |
| The amplitude of a waveform is measured in | millimeters |
| The ability of cardiac muscle cells to respond to an outside stimulus | Excitability |
| The a in aVR, aVL and aVF | Augmented |
| In leads I and II the right arm is | Negative |
| This medication will increase the heart rate and force of contraction | Epinephrine |
| A ? pacemaker is a pacemaker site other than the SA node | Escape |
| Several waveforms | Complex |
| The spread of an impulse through tissue already stimulated | Reentry |
| When the inside of a cell is more negative then the outside | Polarized |
| The stimulus that alters the electrical charges across the cell membrane may be electrical mechanical or ? | Chemical |
| Depolarazition is caused by the movement of ? into the cell | Sodium |
| Each electrode placed in the V position is a | Positive electrode |
| Rate of SA node | 60-100 |
| Rtae of the AV node | 40-60 |
| rate of the ventricles | 20-40 |
| Four properties of cardiac cells | 1.Automaticity 2.Excitability 3. Conductivity 4.Contractility |
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nju9552
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