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Chemical Synapse – Basic Structure

Chemical Synapse – Basic Structure

Author: Scott A. Sheffield MS

Last update: Sep 28th, 2022

The most common type of neuron synapse is the chemical synapse.

An image showing the chemical synapse between 2 neurons, there are labels for (presynaptic neuron, postsynaptic neuron and the synapse)

An image showing the chemical synapse between 2 neurons, there are labels for (presynaptic neuron, postsynaptic neuron and the synapse)

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At chemical synapses, the presynaptic neuron is separated from the postsynaptic neuron by a narrow (20 nm), water-filled space called the synaptic cleft.

An image showing the chemical synapse, the image contains synaptic knob and post synaptic membrane which is expaned

An image showing the synaptic cleft (which is labeled) of a chemical synapse, the image contains synaptic knob and post synaptic membrane which is expaned

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Neurotransmitter molecules are used by the presynaptic neuron to send a message across the cleft to the postsynaptic neuron.
The neurotransmitter molecules are stored in synaptic vesicles located in the expanded tips (or synaptic knobs) of the presynaptic neuron.

An image showing the chemical synapse, the image contains synaptic knob and post synaptic membrane which is expaned

An image showing the synaptic vesicle (labeled) of a presynaptic neuron, the image contains synaptic knob and post synaptic membrane which is expaned

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Action potentials (or electrochemical impulses) at the synaptic knob signal the synaptic vesicles to fuse with the presynaptic membrane and release their contents into the synaptic cleft. Some of the transmitter molecules diffuse across the synaptic cleft and bind with receptors in the postsynaptic membrane.

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

An image showing the synaptic vesicles of the synaptic knob fusion with the presynaptic membrane releasing their content into synaptic cleft

The bound transmitter causes channels in the postsynaptic membrane to open.
Ions diffuse through the open channels, and the exchange either excites (depolarizes) or inhibits (hyper-polarizes) the postsynaptic neuron.

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An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

An image showing ion diffusion process through channels on the postsynaptic membrane

Transmission at chemical synapses is slower than at electrical synapses. It is also slower than the rate at which action potentials move down axons. The reduced rate of current flow at the chemcial synapses is known as synaptic delay.