BIOL 1119 Lecture Notes - Lecture 6: Qrs Complex, T Wave, University Of Manchester
1 Feb 2017
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Document Summary
Sinus rhythm: triggered by sa node: adult at rest 70-80 bpm. Premature ventricular contraction (extrasystole): caused by hypoxia, electrolyte imbalance (k/ca), simulants, stress. Ventricular fibrillation: serous arrhythmia caused by electrical signals arriving at different times to different regions of myocardium: no coordination b/t cardiocytes uncoordinated heart contraction. Gradual depolarization (slowly more positive): from -60mv. A steady inflow of na (gradual shift towards depolarization) without a compensating outflow of k. As near threshold, a special transient, fast-opening, voltage gated calcium channel on pacemaker cells opens extra positive boost: quickly allows ca to give final posture boost to help pacemaker cells reach threshold. Produces slowly rising, depolarizing phase; peaks slightly above 0 mv: no na enters during depolarization phase of ap in nodal cells. Special slow entry sodium channels gradually open again. Each depolarization of sa node creates one heartbeat: sends signals through the whole conduction system.
