On 28 Mar 2006 11:39:25 -0800, feedbackdroids at yahoo.com wrote:
>> Are "distant connections" between neurons direct or indirect? If neuron
>> A from one brain region is connected to neuron B in another brain
>> region, is neuron A's axon really long so that it can directly connect
>> to neuron B's dendrites, or is neuron A indirectly connected to neuron
>> B by way of other neurons (i.e., C, D, E, etc.)?
>The longest axon of a human motoneuron can be over a meter long,
>reaching from the base of the spine to the toes, while giraffes have
>single axons running along the whole length of their necks, several
>meters in length.
I believe the longest axon is even longer than what you describe. The
motor fibers to muscles in the foot start near the base of the spine,
but the sensory fibers from the toes that have their cell bodies in
the dorsal root ganglion near the base of the spine send an axonal
branch up the dorsal root columns to the top of the spinal cord.