BPK 205 Lecture Notes - Lecture 19: Qrs Complex, Tachycardia, Ventricular Fibrillation

• School: Simon Fraser University
• Department: Biomedical Physio & Kines
• Course: BPK 205
• Professor: Nadine Wicks

Document Summary

Cardiac action potentials, electrical conduction, and the ecg. In skeletal muscle, the muscle activity occurs after the ap (since. Ap is so quick), so multiple stimuli can be summed together. Pacemaker aps are driven by funny channels: no stable rmp, pacemaker aps are due to if current through funny channels, hcn channels = hyperpolarization activated cyclic nucleotide gated channels. Funny because they open to hyperpolarization (not depolarization: allows both na+ and k+ to flow -> net na+ in leads to depolarization. Purkinje fibers: sets the pace of the heartbeat at ~70 bpm. If there is a problem with the sa node, av node can take over. Purkinje fibers activity: can also act as pacemaker if both sa and av nodes fail (fires at ~35 bpm) **the hr is set by the fastest pacemaker cells in the circuit = sa node under normal circumstances) ***one sa node ap = one heart beat blood up and out of the ventricle.