Illustration of the anatomy and physiology of a neuron and synapse. Each neuron is made up of a cell body, dendrites and an axon. Information circulates from the dendrites to the cell body, then in the axon to the axonal terminals which connect to the dendrites or cell body of the following neuron. When a signal, or action potential, arrives at an axonal terminal, the relevant neurons in the memory release glutamate, the main excitatory neurotransmittor. When the signal arrives in the presynaptic neuron, vesicles containing glutamate merge with the neuron membrane, releasing their contents into the intersynaptic space. In this example, the postsynaptic neuron contains two of the four subtypes of glutamate receptor : NMDA and AMPA. These receptors are channels that respectively let calcium ions and sodium ions through. Generally, the NMDA channel is blocked by a large volume of magesium ion, which prevents the ions from getting through. When glutamate latches onto AMPA receptors, positive ions enter the postsynaptic neuron, stimulating it.
