describe how nmda channels open
when the nmda gated channel opens, Ca and Na enter the cell but the magnitude of this inward ionic current depends on the postsynaptic membrane potential in an unusual way, for an unusual reason. When glutamate binds the nmda receptor, it becomes opened, but it is clogged by a magnesium ion. Mg pops out of the pore only when the membrane is depolarized, which usually follows the activatio of AMPA channels at the same and neighboring synapses. Thus, inward ionic current through the NMDA channel is voltage dependent.