Final answer:
NMDA receptors are gated by glutamate binding and require depolarization to remove a magnesium block, allowing calcium ions to enter the neuron. This is crucial for intracellular signaling related to synaptic plasticity and memory.
Step-by-step explanation:
The NMDA receptor is gated by glutamate binding, and its activation occurs colloquially after a depolarization event of the postsynaptic membrane removes a magnesium ion (Mg2+) that is otherwise blocking the channel. Once this Mg2+ block is removed, the receptor becomes permeable to calcium ions (Ca2+), which are then able to enter the neuron. This calcium influx can initiate various intracellular signaling pathways that are crucial for processes such as synaptic plasticity and memory formation. Therefore, the correct answer to the question is B) Glutamate; Calcium ions; Depolarization.