T-type calcium channel

T-type calcium channels are low-voltage activated calcium channels that open during membrane depolarization. These channels aid in mediating calcium influx into cells after an action potential or depolarizing signal. The entry of calcium into various cells has many different physiological responses associated with it. Within cardiac and smooth muscle cells voltage-gated calcium channel activation initiates contraction directly by allowing the cytosolic calcium concentration to increase. Not only are T-type calcium channels known to be present within cardiac and smooth muscle, but also are present in many neuronal cells within the central nervous system. Different experimental studies within the 1970s allowed for the distinction of T-type calcium channels (transient opening calcium channels) from the already well-known L-type calcium channels (Long-Lasting calcium channels). The new T-type channels were much different from the L-type calcium channels due to their ability to be activated by more negative membrane potentials, had small single channel conductance, and also were unresponsive to calcium antagonist drugs that were present. These distinct calcium channels are generally located within the brain, peripheral nervous system, heart, smooth muscle, bone, and endocrine system.