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Axon terminals (also called terminal boutons, synaptic boutons, end-feet, or presynaptic terminals) are distal terminations of the branches of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell that conducts electrical impulses called action potentials away from the neuron's cell body to transmit those ...
An axon can divide into many branches called telodendria (Greek for 'end of tree'). At the end of each telodendron is an axon terminal (also called a terminal bouton or synaptic bouton, or end-foot). [20] Axon terminals contain synaptic vesicles that store the neurotransmitter for release at the synapse. This makes multiple synaptic connections ...
The area in the axon that holds groups of vesicles is an axon terminal or "terminal bouton". Up to 130 vesicles can be released per bouton over a ten-minute period of stimulation at 0.2 Hz. [ 1 ] In the visual cortex of the human brain, synaptic vesicles have an average diameter of 39.5 nanometers (nm) with a standard deviation of 5.1 nm.
The brachial plexus is divided into five roots, three trunks, six divisions (three anterior and three posterior), three cords, and five branches.There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches, such as the subscapular nerve, the thoracodorsal nerve, and the long thoracic nerve, [1] that leave the plexus at various points along its length. [2]
These varicose axons resemble strings of beads with varicosities 0.5–2.0 μ in diameter and 1 to 3 μ in length and separated by inter-varicosity axon 0.1 to 0.2 μ in diameter. The varicosities occur at 2–10 μm intervals and it has been estimated that a single adrenergic axon may have over 25,000 varicosities on its terminal part.
Many of the extensions are cytoplasmic protrusions such as the axon and dendrite of a neuron, known also as cytoplasmic processes. Different glial cells project cytoplasmic processes. In the brain , the processes of astrocytes form terminal endfeet , foot processes that help to form protective barriers in the brain.
At the furthest end, the axon loses its insulation and begins to branch into several axon terminals. These presynaptic terminals, or synaptic boutons, are a specialized area within the axon of the presynaptic cell that contains neurotransmitters enclosed in small membrane-bound spheres called synaptic vesicles. [citation needed]
The action potential, which typically starts at the axon hillock, propagates down the length of the axon to the axon terminals where it triggers the release of neurotransmitters, but also backwards into the dendrite (retrograde propagation), providing an important signal for spike-timing-dependent plasticity (STDP). [4]