PHGY 210 Lecture Notes - Lecture 3: Intercalated Disc, Gap Junction, Qrs Complex
18 Mar 2017
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Intercalated disc: cardiac cells have long-axis, cylinders, 100 um, all fibers oriented in same direction, ap propagated along long axis of the cell. Typical ecg: first deflection is the p wave, the qrs complex followed by t wave, extracellular recoding much smaller than intracellular, amplitude about 1mv (opposed to about 130 mv for intracellular ap -90mv -- Action potentials: typical ap of ventricular muscle, put electrode into cell and one outside, resting potential of working myocardial cells (contracting ones) = -90 mv (vs. - 60mv for neuron: resting potential more hyperpolarized, much longer duration of ap than nerve/skeletal muscle, neurons 10ms this, 300ms long. If membrane only permeable to potassium, then membrane potential = equilibrium potential of k+ (-90mv) --at rest: very rapid activation of na channels, but very soon after open they inactivate. Inside of the cell is negative, which also attracts na ions: depolarization phase.
