Strange nerves ?!?!?

[chuinhen]

THeres a different between sympathetic & parasympathetic system

that is

 

FOr the sympathetic system : the preganglionic nerve is shorter

For the parasympathetic system: The preganglionic nerve is longer ?!?!?!

 

Wat is the purpose ??

[Kyrisch]

The purpose of the actual systems (I don't really know why the two nerves are different lengths) are this:

 

The Sympathetic Nervous System is responsible for high-stress situations; it controls various changes in the body like a slow in digestion, an increase in heart rate, and an activation of the Adrenal Glands.

 

The PNS has basically a reciprocal function, increase metabolic rate, slowing the heart beat, etc. After the threat has passed, the PNS brings the body from the "fight or flight" condition back to homeostatis.

 

Albeit an oversimplified view, it is a pretty effective one.

[chuinhen]

u r right on the facts !!

 

But im asking How does the difference in length of ganglionic neurone contribute to it ?!?!

[Glider]

The sympathetic division has short pre-ganglionic fibres because the ganglia run down each side of the spine and are connected. This allows each part of the system to work 'in sympathy' (hence the name). The parasympathetic division has long pre-ganglionic fibres as the ganglia are not connected and reside in the effector organs (glands, blood vessels etc.).

[chuinhen]

ganglia ?? Do u mean the swelling part ???

 

All neurones from the CNS are motor neurones (efferent neurone)..

 

So . the motor neurones do not

pass through the ganglia ( observed from cross section of spinal cord ) ??!?!!

[Glider]

ganglia ?? Do u mean the swelling part ???

Yes. Ganglion refers to a collection of neuron cell bodies outside of the CNS. In the CNS (brain & spinal cord) such collections are called nuclei.

 

In the sympathetic division of the autonomic nervous system (ANS), the cell bodies of the sympathetic fibres form a connected chain of ganglia that run down each side of the spine. This (as I say) allows the entire sympathetic division of the ANS to act in sympathy with itself.

 

All neurones from the CNS are motor neurones (efferent neurone).

I'm not sure what you mean here. All ANS neurones are efferent, yes. Both the sympathetic and parasympathetic fibres effect changes, but opposite to each other.

 

If you're referring to all neurones projecting from the 31 pairs of spinal nerves, then many are afferent. In the peripheral nervous system (PNS) all efferent neurones project from the ventral horns of the spinal cord and all afferent fibres enter via the dorsal horns.

 

So . the motor neurones do not pass through the ganglia ( observed from cross section of spinal cord ) ??!?!!

sympathetic ANS neurones do because the ganglia are formed from their cell bodies.

 

Most PNS motor neurones have their cell bodies in the ventral horns of the spinal cord, so they do not pass through the sympathetic ganglia.

 

The PNS and the ANS are separate and independent systems.