The L-type calcium channel is a subtype of the voltage-regulated calcium channels. The letter L represents the long duration of this channel's activation.
L-type calcium channels occur in muscle cells and in neurons, among other things. The central part of these channels, the α subunit, is encoded by genes from the CACNA1 family.
Many animal cells are triggered to perform a particular action by increasing the concentration of calcium ions in the cytoplasm. The L-channels play an important role in the inflow of these ions from outside the cell. They are triggered by a (sudden) increase in cell membrane potential, an action potential. Further increase in calcium concentration in the cell may still occur because calcium intake activates the Ryanodin receptors, which then release calcium from the sarcoplasmic reticulum (SR). In muscle cells, the increased calcium concentration leads to contraction of the cell; in cells of glands for secretion of fluid. After the action potential, the calcium ions are pumped back, partly the cell (through the sarcolemmal calcium pump and the sodium calcium exchanger) and partly to the SR through the SR calcium pump.
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