<unk> s <unk>  are a group of<unk> -gated ion channels found in excitable cells  (e.g., muscle, glial cells, neurons, etc.) with a permeability to the ion Ca2+.  At physiologic or resting membrane potential,<unk> s are normally closed. They are activated (i.e., opened) at depolarized membrane potentials and this is the source of the<unk><unk> " epithet.  Activation of particular<unk> s allows Ca2+ entry into the cell, which depending on the cell type, results in muscular contraction, excitation of neurons, up-regulation of gene expression, or release of hormones or neurotransmitters.
Voltage-dependent calcium channel
Calcium channel
Cyclic nucleotide-gated ion channel
Voltage-gated ion channel
Sodium channel
Sodium calcium exchanger
Light-gated ion channel
Chloride channel