Axoplasm

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Axoplasm
Details
Part ofAxon of a nerve
SystemNervous system
Identifiers
Latinaxoplasma
THH2.00.06.1.00019
Anatomical terminology

Axoplasm is the cytoplasm within the axon of a neuron (nerve cell). For some neuronal types this can be more than 99% of the total cytoplasm.[1]

Axoplasm has a different composition of

soma) or dendrites. In axonal transport
(also known as axoplasmic transport) materials are carried through the axoplasm to or from the soma.

The

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.

Structure

Axoplasm is composed of various organelles and cytoskeletal elements. The axoplasm contains a high concentration of elongated

protein complexes.[5]

Function

Signal transduction

Axoplasm is integral to the overall function of neurons in propagating action potential through the axon. The amount of axoplasm in the axon is important to the cable like properties of the axon in cable theory. In regards to

synaptic cleft
.

Damage detection and regeneration

Axoplasm contains both the mRNA and ribonuclearprotein required for axonal protein synthesis. Axonal protein synthesis has been shown to be integral in both

neural regeneration and in localized responses to axon damage.[5] When an axon is damaged, both axonal translation and retrograde axonal transport are required to propagate a signal to the soma that the cell is damaged.[5]

History

Axoplasm was not a main focus for neurological research until after many years of learning of the functions and properties of

glial cells.[6] To solve this problem squid axons were used as an animal model due to the relatively vast sized axons compared to humans or other mammals.[7] These axons were mainly studied to understand action potential, and axoplasm was soon understood to be important in membrane potential.[8] The axoplasm was at first just thought to be very similar to cytoplasm, but axoplasm plays an important role in transference of nutrients and electrical potential that is generated by neurons.[9]

It actually proves quite difficult to isolate axons from the myelin that surrounds it,[10] so the squid giant axon is the focus for many studies that touch on axoplasm. As more knowledge formed from studying the signalling that occurs in neurons, transfer of nutrients and materials became an important topic to research. The mechanisms for the proliferation and sustained electrical potentials were affected by the fast axonal transport system. The fast axonal transport system uses the axoplasm for movement, and contains many non-conductive molecules that change the rate of these electrical potentials across the axon,[11] but the opposite influence does not occur. The fast axonal transport system is able to function without an axolemma, implying that the electrical potential does not influence the transport of materials through the axon.[12] This understanding of the relationship of axoplasm regarding transport and electrical potential is critical in the understanding of the overall brain functions.

With this knowledge, axoplasm has become a model for studying varying cell signaling and functions for the research of neurological diseases like

Huntington's.[14]
Fast axonal transport is a crucial mechanism when examining these diseases and determining how a lack of materials and nutrients can influence the progression of neurological disorders.

References

  1. PMID 7541635
    .
  2. ^ Hammond, C. (2015). "Cellular and Molecular Neurophysiology". Elsevier: 433. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Brady, S. T. (1993). Axonal dynamics and regeneration. New York: Raven Press. pp. 7–36.
  4. PMID 24068803
    .
  5. ^
    PMID 15473850
    .
  6. PMID 1260
    .
  7. ^ Young, J. (1977). What squids and octopuses tell us about brains and memories (1 ed.). American Museum of Natural History.
  8. doi:10.1002/jcp.1030220209
    .
  9. PMID 7678421
    .
  10. S2CID 30934150
    .
  11. S2CID 4327023
    .
  12. PMID 6183745
    .
  13. PMID 21734277
    .
  14. PMID 19525941
    .
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