KINE 3012 Lecture Notes - Lecture 12: Cardiac Action Potential, Atrioventricular Node, Cardiac Muscle
3 Dec 2013
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How we regulate heart rate and pace maker potential. No different than any other action potential, when it reaches threshold. As it gets closer to threshold, membrane potential increases. Na and ca enter the cell, k leaves the cell. K channels close and na channels open. When threshold is reached ca channels open, calcium leads to the action potential fire. Calcium channels stays open for awhile, huge rush in of positive charge into the cell. Increased potassium levels leak out through opened k channels. If our low resting heart rate, it allows us to increase it to a 100 aps/minute. Av nodes do not beat on their own. You can"t have another firing within 250msec. If your heart doesn"t relax, it can"t fill with blood. Heart has leaky k channels, k is allowed to come out, drops to -90 mv. As more na enters into the cell, more na channels open *positive feedback* Hit maximum really fast, na channels close.
