BIOL 1119 Lecture Notes - Lecture 6: Ventricular Fibrillation, Pacemaker Potential, Threshold Voltage

• School: Northeastern University
• Department: Biology
• Course: BIOL 1119
• Professor: Christopher Richardson

Document Summary

Cardiac rhythm: systole: ventricular contraction, diastole: ventricular relaxation, sinus rhythm: triggered by the sa node adult at rest is 70 to 80 bpm, premature ventricular contraction (extrasystole) caused by hypoxia, electrolyte imbalance, stimulants, stress, arrhythmia: abnormal cardiac rhythm. Ventricular fibrillation is a serious arrhythmia caused by electrical signals arriving at different times to different regions of myocardium; no coordination between cardiocytes, thus uncoordinated heart contractions begin. Depolarization of sa node: sa node: no stable resting membrane potential (no rmp, pacemaker potential. Gradual depolarization (depolarizing) (slowly more positive) from -60 mv. A steady inflow of na+ without a compensating outflow of k+ Na+ enters through a special type of channel found only in pacemaker cells (particularly sa node): unlike most volt-gated ion channels these special channels open only when the membrane potential is at negative values. Most volt-gated ion channels open when positive or when less negative values (as they depolarize)