About the length of neuron

[funbari]

Hello everyone,
I'm now studying about the nervous system (i'm in secondary school presently). And I just know about some basic of neurones, however many of my classmates want to know how long can a neuron be. Can anyone help?
Thank you very much!!

[sdekivit]

neurons can be very short (interneurons in the gray matter of the spinal cord) and very long, for example the nerve transporting signals from the central nervous system to the top of my toe. This can be a few metres long.

[MrMistery]

I think the minimum is 4 microns: small granular neurons. maximum is, as sdekivit said, even 2 meters long...

[funbari]

Thank you very much!!! As I really cant find the answer in my books.

But I've got more questions: Is that the number of neurones between cns and receptor can be more than one? If that's true, why neuron need to be so long?(It can connect with many neuron in order to transmit nerve impulse in a very long distance.)
*The above is a question from one of my classmate...

[MrMistery]

Usually there are 3 neurons on the path from the receptor to the cortex. However, there are usually 2 neurons from the cortex to the effector.(is that a word in English?)
Why? simple. Speed. It takes 0.5 miliseconds for the neurotransmitter to reach the postsinaptic neuron, so the more sinapses you have, the more time it will take. Also, it would be a waste of energy to get all the celullar mechanisms working in order for the synapse to happen
Regards,
Andrew

[funbari]

Wow, that's very detail, thank you very much, you explained it very well!!

[MrMistery]

You're welcome. That's what we are here for. Answering questions is a really good way to revise my nervous system

[Navin]

Is the time taken at the synapse quite long?

[MrMistery]

0.5 miliseconds. Doesn't seem long, but with sinapses, speed is at the essence, otherwise you would move like in a rerun

[victor]

Why? simple. Speed. It takes 0.5 miliseconds for the neurotransmitter to reach the postsinaptic neuron, so the more sinapses you have, the more time it will take. Also, it would be a waste of energy to get all the celullar mechanisms working in order for the synapse to happen
Regards,
Andrew

Also, if there're more synapses...it means more neurotransmitter needed..you know that some neurotransmitter are essential (e.g. acetylcholine have to be supplied by some nutrient like lecythine/phosphatidylcholine)...doesn't seem efficient for our bodies eh?