BIOL 121 Lecture Notes - Lecture 30: Pacemaker Potential, Cardiac Muscle, Membrane Potential

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22 Dec 2020
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Instead, there is a partial repolarization caused by transient k+ channels, and then the membrane remains depolarized at a plateau of ~0mv. Ca2+ ions just balances flow of k+ ions out of the cell, keeping the membrane depolarized at the plateau value: repolarization: eventually occurs due to inactivation of l-type ca2+ channels and opening of another subtype of k+ channels. Nodal cell aps: part of the conducting system; no steady resting potential, but instead, undergoes slow depolarization (called pacemaker potential, which brings the membrane potential to threshold ap) Although sa & av nodal cells have similar aps, sa nodal cells are much faster which is why they normally initiate aps and determine heart rate. 1st pacemaker channel) progressive reduction in k+ membrane permeability. The k+ channels that opened in response to repolarization phase of the previous ap begin to close due the membrane"s return to negative potentials.

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