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Axonal transport, also called axoplasmic transport or axoplasmic flow, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other organelles to and from a neuron's cell body, through the cytoplasm of its axon called the axoplasm. [1]
It forces the vesicle's membrane to fuse with the presynaptic membrane, releasing their content into the synaptic cleft within 180 μs of calcium entry. [ 2 ] [ 3 ] [ 4 ] When receptors in the postsynaptic membrane bind this neurotransmitter and open ion channels , information is transmitted between neurons (A) and neurons (B). [ 5 ]
A diagram of the proteins found in the active zone. The active zone is present in all chemical synapses examined so far and is present in all animal species. The active zones examined so far have at least two features in common, they all have protein dense material that project from the membrane and tethers synaptic vesicles close to the membrane and they have long filamentous projections ...
The precise mechanism of slow axonal transport remains unknown but recent studies have proposed that it may function by means of transient association with the fast axonal transport vesicles. [4] Though axonal transport is responsible for most organelles and complex proteins present in the axoplasm, recent studies have shown that some ...
Calcium ions then bind to synaptotagmin proteins found within the membranes of the synaptic vesicles, allowing the vesicles to fuse with the presynaptic membrane. [16] The fusion of a vesicle is a stochastic process, leading to frequent failure of synaptic transmission at the very small synapses that are typical for the central nervous system .
Motor proteins are the driving force behind most active transport of proteins and vesicles in the cytoplasm. Kinesins and cytoplasmic dyneins play essential roles in intracellular transport such as axonal transport and in the formation of the spindle apparatus and the separation of the chromosomes during mitosis and meiosis.
Defects encompass improper sorting of cargo into transport carriers, vesicle budding, issues in movement of vesicles along cytoskeletal tracks, and fusion at the target membrane. Since the life cycle of the cell is a highly regulated and important process, if any component goes awry there is the possibility for deleterious effects.
The axonal initial segment (AIS) is a structurally and functionally separate microdomain of the axon. [ 6 ] [ 7 ] One function of the initial segment is to separate the main part of an axon from the rest of the neuron; another function is to help initiate action potentials. [ 8 ]