Synapse / synaptic cleft

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Synapse, also called synaptic cleft or gap: Synapses are contact points where one neuron’s axon terminal nearly touches the dendrites of another neuron. This 20-40 nanometer-wide gap allows neurons to communicate and pass signals. It’s also where electrical signals (triggered action potentials) are converted (transduced) into chemical signals (neurotransmitters) that can be perceived by the next neuron. After the synapse, the signal is promptly reconverted into electrical signals as information continues up the axon to reach the next neuron until the message reaches either the brain or returns to the peripheral organs. Synapses are between opposing terminals:

• Presynaptic (before the synapse) terminals on the axon terminal is where synaptic vesicles transduce electrical to chemical signals released into the synaptic cleft.

• Postsynaptic (after the synapse) terminals are in the neuron’s soma-dendritic region (where dendrites extend from the nerve cell body or neuron soma). Neurotransmitters bind to receptors on the dendrite membrane

Neurons can have a few-to-100,000s of synapses, which connect with themselves, other neurons, or neurons in other parts of the brain. The brain’s cerebral cortex has 100 trillion synapses — forming about 10,000 every 15 minutes during development. Synaptic networks allow for complex thoughts and consciousness. They can also be implicated in Parkinson’s disease and depression. There are two types of synapses:

• Electrical synapses are faster and are good for quick reactions like reflexes.

• Chemical synapses are slower and are important for learning and memory