Final answer:
The NMDA receptor is activated when glutamate binds to the receptor simultaneously with the membrane's depolarization, which removes the inhibitory magnesium ion, allowing calcium ions to enter the neuron and facilitate synaptic plasticity.
Step-by-step explanation:
The NMDA receptor is a sophisticated ion channel in the brain's neurons, possessing specific conditions for activation. It operates as a glutamate receptor but also requires concurrent membrane depolarization to commence its function. The NMDA receptor becomes activated when glutamate binds to the receptor while the membrane is depolarized. This depolarization removes an inhibitory magnesium ion, allowing the receptor to open and permit the influx of calcium ions, which play critical roles in synaptic plasticity and other neuronal processes.
Once the Mg2+ blockage is evicted due to depolarization, the receptor becomes permeable, which facilitates the entry of calcium ions into the neuron. This entry of calcium is consequential for synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), which are fundamental for learning and memory processes. Hence, the NMDA receptor's operation is vital for communication and plasticity within the brain's neural circuits.