HLSC 3P90 Lecture Notes - Lecture 18: Sinus Bradycardia, Sinus Rhythm, Resting Potential
15 Dec 2019
School
Department
Course
Professor
Document Summary
Abnormalities of the normal electrical rhythm of the heart. Tachycardias (tachyarrhythmias) abnormally fast rhythms: supraventricular involving av node, ventricular originating from the his-purkinje system. Less negative threshold potential: no fast na+ channels. Native pacemaker = sa node sets the heart rate. Overdrive suppression = cells with fastest rhythm dominate and directly suppress other automatic cells. Latent pacemakers (ectopic/non-sinus) = harbor potential to act as pacemakers if needed. The automatic cells in the specialized conduction pathway have different intrinsic firing rates which are determined by three factors: 1) rate of phase 4 depolarization. 2) maximum negative resting membrane potential: 3) threshold potential. Alterations in impulse initiation by the sinus node or by latent pacemakers are regulated by neurohumoral factors (sns, pns, and humoral facto) Arrhythmias may arise from altered impulse formation at the sa node or from other sites including the specialized conduction pathway or regions of cardiac muscle. Main abnormalities of impulse initiation that leads to arrhythmias: 1.
