BIOL 1119 Lecture Notes - Lecture 6: Pacemaker Potential, Resting Potential, Sinus Rhythm
28 Jan 2017
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Karina da rosa: the circulatory system : the heart, background. Ecg i: detects the heart"s electrical current and produces a graph, electrical and contractile activity of the heart, cardiac rhythm. Extrasystole: premature ventricular contraction, hypoxia (oxygen, electrolyte imbalance (k + ca, stimulants, stress iv. Sinus rhythm: defined by the sa node, adult rest : 70 to 80 bpm v. Arrhythmia: abnormal cardiac rhythm, electrical signals arriving at many different times in the myocardium : no coordination causing whack contractions, depolarization of sa node i. Sa node: no stable resting membrane potential, pattern constant increase towards positive ii. Pacemaker potential: gradual depolarization : threshold is approached as time goes on, becomes more positive from -60 mv, caused by an increase in na + i. ii. Only open when the membrane potential is at a negative value iii. At threshold: transient, fast-opening, voltage gated calcium channels on pacemaker cells open, action potential of the sa node i.
