Final answer:
Long-term potentiation (LTP) refers to the strengthening of a synaptic connection, often involving calcium entry through NMDA receptors leading to the insertion of more AMPA receptors into the postsynaptic membrane, increasing its responsiveness.
Step-by-step explanation:
The statement that best describes long-term potentiation (LTP) is 'More sodium entering the postsynaptic membrane per presynaptic action potential' which is somewhat incomplete. The more accurate description is that there is more calcium entering the postsynaptic neuron, leading to the insertion of additional AMPA receptors into the postsynaptic membrane, which in turn increases the neuron's responsiveness to neurotransmitters. This synaptic strengthening is a key mechanism for learning and memory.
LTP is a process where repeated stimulation of a synapse can lead to an increased potency of synaptic transmission. The underlying mechanism involves the NMDA receptor being depolarized by multiple presynaptic inputs, forcing out magnesium ions and allowing calcium ions to enter the postsynaptic neuron. Calcium then initiates a signaling cascade that causes the insertion of additional AMPA receptors into the postsynaptic membrane. Subsequent release of neurotransmitter from the presynaptic neuron becomes more effective in depolarizing the postsynaptic neuron, making it more likely to fire an action potential.