BIOL 1119 Lecture Notes - Lecture 6: Atrioventricular Node, Systolic Geometry, T Wave
4 Feb 2017
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Document Summary
Sinus rhythm: triggered by the sa node: adult at rest is 70 to 80 bmp. Premature ventricular contraction (extrasystole: caused by hypoxia, electrolyte imbalance, stimulants, stress, extra electrical events that come from conduction systems separate from the sa node. Ventricular fibrillation is a serious arrhythmia caused by electrical signals arriving at different times to different regions of the myocardium: no coordination, thus uncoordinated heart contractions. Sa node: no stable resting membrane potential. Allows calcium to come into nodal cell quickly to give a quick final positive boost to reach threshold in nodal cell. Action potential: occurs at threshold (-40 mv) Special voltage-gated calcium channels (l type calcium channels) open which are slow-opening and long lasting. These l-type ca2+ channels allow calcium to enter into the nodal cells. This depolarizes the membrane more slowly than the normal fast opening, fast entry na+ channels on skeletal and heart muscle and on nerve cells (when move toward positive)
