Module 3: Figure Ca2+ entry mechanisms
Entry of Ca2+ through agonist-operated channels.
Entry of external Ca2+ can be activated by stimuli arriving at the cell surface or by signals generated within the cell. The most direct mechanism occurs in the receptor-operated channels (ROCs), where the agonist binds directly to the ion channel. Agonists can also activate entry indirectly by recruiting various internal signalling pathways to activate second messenger-operated channels (SMOCs) or a store-operated channel (SOC) as described in the text.