Axoplasm
| Axoplasm | |
|---|---|
| Details | |
| Identifiers | |
| Latin | axoplasma |
| Code | TH H2.00.06.1.00019 |
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Anatomical terminology
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Axoplasm is the cytoplasm within the axon of a neuron (nerve cell). Neurites (axons and dendrites) contain about 99.6% of the cell’s cytoplasm, and 99.7% of that is in the axons.
Axoplasm has a different composition of organelles and other materials than that found in the neuron's cell body (soma) or dendrites. In axoplasmic transport, materials are carried through the axoplasm to or from the soma.
The electrical resistance of the axoplasm, called axoplasmic resistance, is one aspect of a neuron's cable properties, because it affects the rate of travel of an action potential down an axon. If the axoplasm contains many molecules that are not electrically conductive, it will slow the travel of the potential because it will cause more ions to flow across the axolemma (the axon's membrane) than through the axoplasm.
Axoplasm is composed of various organelles and cytoskeletal elements. The axoplasm contains a high concentration of elongated , neural filaments, and microtubules. Axoplasm lacks much of the cellular machinery (ribosomes and nucleus) required to transcribe and translate complex proteins. As a result, most enzymes and large proteins are transported from the soma through the axoplasm. Axoplasmic transport occurs either by fast or slow transport. Fast transport involves vesicular contents (like organelles) being moved along microtubules by motor proteins at a rate of 50-400mm per day. Slow axoplasmic transport involves the movement of cytosolic soluble proteins and cytoskeletal elements at a much slower rate of 0.02-0.1mm/d. The precise mechanism of slow axoplasmic transport remains unknown but recent studies have proposed that it may function by means of transient association with the fast axoplasmic transport vesicles. Though axoplasmic transport is responsible for most organelles and complex proteins present in the axoplasm, recent studies have shown that some translation does occur in axoplasm. This axoplasmic translation is possible due to the presence of localized translationally silent mRNA and ribonuclearprotein complexes.
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