Why does the autonomic nervous system have neruones which are mostly non-myelinated?

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rice7
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Also what exactly are ganglions?
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Picture~Perfect
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(Original post by rice7)
Also what exactly are ganglions?
Do you know what the purpose of a myelin sheath is and what the autonomic nervous system is responsible for, if so why do you think it might not be as beneficial to have myelinated neurones in that region of the nervous system?

I don't know if you have come across the term ganglion before but it simply means a collection of nerve cells.
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Dynamo123
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(Original post by rice7)
Also what exactly are ganglions?
The purpose of a myelin sheath, is to act as an insulator. Normally this would hamper the velocity of conduction of impulses, if it were not for a specific method of saltatory conduction, involving Nodes of ranvier occurring in an intermittent fashion along the myelin sheath. Based on this function, I think you can appreciate why neurons of the autonomic NS are usually non-myelinated. Also note that technically speaking, only the post-ganglionic axons of the ANS are unmyelinated. The preganglionic axons are considered myelinated.

A ganglion is a collection of nerve cell bodies (although some definition contain the neuritic process called dendrites as well) outside the CNS. A similar collection inside the CNS is termed as a nucleus--entirely different from the nucleus in every cell of your body.
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KanKan
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You can understand why evolutionary we could benefit from faster conscious responses - explaining the myelinated somatic nervous system.

When it comes to your autonomic nervous system, and what it deals with (gut movement, heart, etc), the energy spent myelinating those neurones is just not worth the extra speed.
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Hype en Ecosse
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(Original post by Dynamo123)
The purpose of a myelin sheath, is to act as an insulator. Normally this would hamper the velocity of conduction of impulses, if it were not for a specific method of saltatory conduction, involving Nodes of ranvier occurring in an intermittent fashion along the myelin sheath. Based on this function, I think you can appreciate why neurons of the autonomic NS are usually non-myelinated. Also note that technically speaking, only the post-ganglionic axons of the ANS are unmyelinated. The preganglionic axons are considered myelinated.
I'm still unclear about this. The presence of myelin sheaths speeds up conductance along the axon. Why would this be a disadvantage for postganglionic fibres?
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Dynamo123
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(Original post by Hype en Ecosse)
I'm still unclear about this. The presence of myelin sheaths speeds up conductance along the axon. Why would this be a disadvantage for postganglionic fibres?
Well, I don't think that they don't have myelin as an advantage. I think there is some anatomical or evolutionary basis, not any physiological basis as to why they don't have myelin; because that creates a sort of a paradox, that Postganglionic sympathetic nerve fibers are involved in responses including fight or flight (which is a sort of a rough way to describe it), and therefore, they would be at an advantage if they were myelinated, which is not the case. It may be due to the relative size of the nerve fiber, but I don't think this can be an important regulating factor.
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