Is Synaptic Cleft Narrow? “Synapses are very small. This narrow gap of extracellular space is approximately 20-40 nanometers (nm) wide. For an idea of scale, one inch is about 25.4 million nm long. What is the size of a synapse? How big is a synapse? Synapses are tiny—you cannot see them with the naked eye.
What Event Occurs At The Synaptic Terminal? At the synaptic terminal (the presynaptic ending), an electrical impulse will trigger the migration of vesicles (the red dots in the figure to the left) containing neurotransmitters toward the presynaptic membrane. What is found at synaptic terminal? The presynaptic axon terminal, or synaptic bouton, is a specialized area