I wonder if physiology professors everywhere hack on about the same things: action potentials in muscle cells, both cardiac and skeletal, and the contents of the cell. So many things I’m more curious about, like the human genome and DNA, transcription, meiosis and mitosis, brain chemistry, kidney function, etc etc. But somehow it seems to me that the longest lessons always wind up being on action potentials, with their sodium and potassium channels, depolarization, and concentration and ion gradients. Maybe it’s just UofO and ESO. Maybe these are just the ones I understood the first time (thanks Grant and Greg!).
So let me explain it to you, to test my knowledge!
The heart has two types of muscle cells: autorhythmic and contractile. Autorhythmic cells control the electric signal that initiates the beat of your heart. Contractile cells cause the actual beat you feel, pumping blood through the body, and coordinate the timing. Both of these work in a never-ending cycle of depolarization and repolarization.
Hokay, so… in autorhythmic cells, like any cell, sodium is constantly being pumped out and potassium is constantly being pumped in by ion pumps that live in the membrane. They do this to Continue reading