| 1. | Almost instantaneously, the whole SA node is sending out a strong electrical charge.
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| 2. | The SA node is found in all amniotes but not in more primitive vertebrates.
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| 3. | Tbx18 transduction converts atrial muscle cells into SA node cells that initiate the heartbeat.
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| 4. | These channels allow for continuous rhythmic bursts that control the SA Node of the heart.
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| 5. | Pacemaker potentials are fired not only by SA node, but also by the other foci.
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| 6. | Retrograde P waves refers to the depolarization from the AV node back towards the SA node.
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| 7. | The cause is a gradual lengthening of conduction time from the SA node to the atria.
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| 8. | Thus, in the normal, healthy heart, only the SA node intrinsic rate is observable.
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| 9. | The superior border of the terminal sulcus designates the transverse plane in which the SA node resides.
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| 10. | Conduction across the SA node is normal until the time of the pause when it is blocked.
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