PSL301H1 Lecture 8: Cardiac Excitability (Jan. 23, 2017)
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PSL301H1 Full Course Notes
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Lecture notes: cardiac excitability - heart rate and ecg. Non-pacemaker cell (myocyte) ap --> this was the focus so far (shown left) Sits at resting potential, waiting for instructions to fire (like a soldier) Generate own ap spontaneously --> removing heart from body may still keep it pumping despite no input from the brain. Slow response ap - slower rate of depolarization. There is no spike up that rush the ions in, unlike myocyte ap. Found in the sinoatrial (sa) and atrioventricular (av) nodes. Hearts spontaneously contracts because of the electrical initiator cells - the pacemakers. Unstable membrane potentials --> polarized to -55 to -62 mv. Slow depolarizing membrane potential compared to resting in muscle cells. Refer to summer table 14-3, pasted below (taken from slide 38 of this lecture) These are permeable to both k and na. The path is shown below with the ions. These are responsible for entry of na in order to bring cell to threshold.
