Synapse
Neuron communicate with other neurons and muscle cells primarily by a chemical synapse. Shown here is a synapse in the central nervous system and is composed of three elements: the terminal bouton (presynaptic terminal) of the presynaptic neuron; a synaptic cleft; and a postsynaptic density of the plasma membrane of the postsynaptic neuron. 50,000x
Presynaptic terminals >
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. Though not visible in this image, numerous mitochondria are also present in the presynaptic terminal for energy production and as a calcium buffer.
- 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. Though not visible in this image, numerous mitochondria are also present in the presynaptic terminal for energy production and as a calcium buffer.
Synaptic cleft >
The synaptic cleft is a narrow space separating the pre- and postsynaptic neurons. The neurotransmitter released from the presynaptic terminal must diffuse cross the cleft to access 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 is called the postsynaptic density. Binding of neurotransmitter to these receptors results in local changes in the membrane potential of 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 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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