In NMDA receptor function, which ion primarily enters the neuron when the channel opens?

In NMDA receptor function, which ion primarily enters the neuron when the channel opens?

• A. Sodium
• B. Calcium
• C. Potassium
• D. Chloride

Answer: (B)

When the NMDA receptor channel opens, it conducts several cations, but the standout consequence is calcium entry. The receptor is uniquely permeable to calcium, and this influx acts as a key intracellular signal that links synaptic activity to long-lasting changes in the neuron. The channel requires both glutamate binding and sufficient depolarization to relieve an Mg2+ block, and once open, calcium enters the postsynaptic cell to activate calcium-dependent signaling cascades (like CaMKII and CREB) that drive synaptic plasticity such as LTP. Sodium also flows through the channel to contribute to the excitatory current, and potassium would leave or have less influence under typical conditions, but the calcium signal is what predominantly carries the important downstream effects for learning and memory.

When the NMDA receptor channel opens, it conducts several cations, but the standout consequence is calcium entry. The receptor is uniquely permeable to calcium, and this influx acts as a key intracellular signal that links synaptic activity to long-lasting changes in the neuron. The channel requires both glutamate binding and sufficient depolarization to relieve an Mg2+ block, and once open, calcium enters the postsynaptic cell to activate calcium-dependent signaling cascades (like CaMKII and CREB) that drive synaptic plasticity such as LTP. Sodium also flows through the channel to contribute to the excitatory current, and potassium would leave or have less influence under typical conditions, but the calcium signal is what predominantly carries the important downstream effects for learning and memory.