The Basis of ECG (19)
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stevenypark Plus on January 27, 2011
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38 terms
Terms | Definitions |
|---|---|
 The initial rapid repolarization of the cardiac action potential from a ventricular myocyte cell is due to _____ channel inactivation and outward flow of _____ (_____ channel). |  Na+ K+ ito *to = transient outward |
| In phase 1 of the ventricular myocyte action potential, voltage-gated _____ Ca2+ channels open in response to depolarization. This slows down the repolarization brought about by the opening of K+ channels. | L-type |
| After the initial opening of potassium channel, another group of channels called _____ channels opens to return the membrane to resting level (ventricular myocyte action potential). |  delayed rectifier |
| During the resting phase, there is a small inward current of Na+ through _____ channels and small K+ outward current by _____ channels (ventricular myocyte action potential). |  ib iK1 |
| Cardiac action potentials travel from cell to cell via low resistance _____. | gap junctions |
| Why do cardiac action potentials travel in one direction? | The cell that depolarizes an adjacent cell undergoes a refractory period. |
| During the _____, a cardiac action potential cannot occur. |  absolute refractory period |
| Repeated stimulation of the motor nerve results in large _____ contractions. | tetanic |
| What kind of muscle cannot create sustained tetanic contractions? | cardiac muscle |
| Phase 4 of the SA node action potential is known as the _____. It occurs due to the inward _____ current (_____ channel) and inward _____ current (_____ channel). |  pacemaker potential Na+ if Ca2+ iCa |
| What type of Ca2+ channels are involved in phase 4 of the SA action potential? | T-type Ca2+ channels |
| When depolarization of the SA node action potential reaches its threshold, _____ Ca 2+ channels open while _____ channels begin to close. |  L-type Ca2+ if |
| Phase 3 of the SA node action potential is known as _____. This is due to closure of _____ channels and opening of _____ channels. |  repolarization Ca2+ K+ |
| In the SA node action potential, the upstroke of action potential is due to the inward _____ current (rather than the inward _____ current). | calcium sodium |
| The rate of _____ of the SA node sets the heart rate. | spontaneous depolarization |
| In the heart, there is a delay in conduction through the _____. This occurs because cells in this structure have higher _____. | AV node electrical resistance |
| The _____ is the only electrical contact between the atria and ventricles. | AV node |
| Do the atria or ventricles contract first? | atria |
| The word "sinus" refers to which node of the heart? | SA node |
| Damaged myocardial muscle cells can generate action potentials spontaneously, leading to _____. | cardiac arrhythmias |
| Which phase of the cardiac action potential will the parasympathetic nervous system act upon? |  phase 4 |
| Acetylcholine activates _____ receptors to activate _____ proteins. This opens _____ channels and increases _____ conductance, which will cause hyperpolarization. The overall effect is to prolong phase _____ of the SA node. | M2 Gi K+Ach potassium ion 4 |
| Acetylcholine can impact the heart in 2 ways. In one pathway, it activates _____ proteins and decreases the enzyme _____. This leads to a decrease in _____ concentrations, which will subsequently lower the enzyme _____. The result is decreased activation of _____ and _____ channels, which slows the rate of spontaneous depolarization of the SA node. Ultimately, these actions prolong phase _____ of the SA node. | Gi adenylate cyclase cAMP protein kinase A if iCa 4 |
| To calculate heart rate from an ECG record, measure the time between the ____ waves. |  R |
| Sympathetic effects on the SA node: Norepinpehrine acts upon cardiac _____ receptors to increase the molecule _____, which induces phosphorylation of _____ and _____ channels. This increases the rate of depolarization and increases heart rate. |  Beta1 cAMP if iCa |
| In an ECG, the P wave corresponds to depolarization of _____. It is the _____ deflection, and its duration is the time it takes to depolarize the _____ myocardium. |  atrial myocytes 1st atrial |
| The P-R interval corresponds to the interval between _____ and _____ activation. Thus, it can be used to record the conduction time between the SA node and ventricular myocardial cells. | atrial ventricular |
| The QRS complex corresponds to _____ depolarization. Its duration is the time to depolarize _____. | ventricular ventricles |
| Which is larger: QRS complex or P wave? Explain. | QRS complex > P wave because the ventricular mass > atrial mass |
| In ECG, _____ is any initial downward deflection followed by an upward deflection. | Q |
| In ECG, _____ is any upward deflection whether or not it is preceded by a Q wave. | R |
| In ECG, _____ is any downward deflection preceded by an R wave. | S |
| The _____ segment corresponds to the plateau of ventricular action potential. All regions of the ventricles are completely _____. | ST depolarized |
| In ECG, the _____ corresponds to repolarizaton of the ventricle. | T wave |
| The _____ interval is between the onset of the QRS complex and end of T wave. | Q-T |
| The _____ interval provides a useful index of ventricular action potential duration. | Q-T |
| Prolonged _____ interval can lead to arrhytmias and death. | Q-T |
| During the _____ interval, all cardiac cells are resting. | T-P interval |
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