Terminals
The synapse, consisting of an axon terminating on another neuron, has three parts: presynaptic element (terminal bouton), synaptic cleft, and post-synaptic cell. This image shows two terminal boutons with synaptic vesicles containing a neurotransmitter. A synaptic cleft separates the terminal bouton from the post-synaptic cell, which exhibits a post-synaptic density. 50,000x
Terminal bouton (presynaptic terminal) >
The presynaptic terminal (terminal bouton) of the presynaptic neuron contains synaptic vesicles filled with neurotransmitter. An action potential triggers calcium influx into the terminal, causing the release of this neurotransmitter into the synaptic cleft.
- Synaptic vesicles
The presynaptic terminal (terminal bouton) of the presynaptic neuron contains synaptic vesicles filled with neurotransmitter. An action potential triggers calcium influx into the terminal, causing the release of this neurotransmitter into the synaptic cleft.
Synaptic cleft >
The synaptic cleft is a narrow space separating the pre- and postsynaptic neurons. The neurotransmitter released from the presynaptic terminal diffuses across the cleft to access the postsynaptic neuron.
Postsynaptic neuron
After the neurotransmitter diffuses across the synaptic cleft, it binds to receptors clustered in the plasma membrane of the postsynaptic neuron immediately opposite the presynaptic terminal. This region of the neuron is called the postsynaptic density. Binding of neurotransmitter to these receptors results in local changes in the membrane potential of the postsynaptic neuron.
- Postsynaptic density >
After the neurotransmitter diffuses across the synaptic cleft, it binds to receptors clustered in the plasma membrane of the postsynaptic neuron immediately opposite the presynaptic terminal. This region of the neuron is called the postsynaptic density. Binding of neurotransmitter to these receptors results in local changes in the membrane potential of the postsynaptic neuron.
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