motor control

falvarez at falvarez at
Mon Dec 9 13:50:04 EST 1996

In article <32A1B252.7F4E at> John King <johnkate at> writes:
>From: John King <johnkate at>
>Subject: motor control
>Date: Sun, 01 Dec 1996 17:29:05 +0100

>Besides the corticospinal tract can someone tell me the neural tracts
>that can affect the alpha motor neuron and what neurotransmitters are

Far too many to mention in a list that makes sense.
I will sumarize to illustrate its complexity, you are better off consulting 
some textbooks.
A large pathway parallel to the corticospinal tract is the 
Rubro spinal system involved also in voluntary movement. Others are related to 
posture and equilibrium control of volunatry movement and reflexes. In general 
they are divided in the Vestibulospinal system (with a lateral and and a 
medial subsystem) and Reticulospinal system (with also a lateral and a medial 
subsystem). Others that are usually mentioned in textbooks are the tectospinal 
systems to coordinate head, neck and upper body movement. Of course real life 
is always more complicated than medical textbooks.

Neurotransmitters are again very varied. Some pathways are inhibitory others 
excitatory. Here is a list of important neurotransmitters in these systems... 
from the top of my head: Glutamate, GABA, Noradrenaline, Dopamine, Serotonin, 
several neuropeptides like substance P, enkephalin, TRH.....

Also different motoneurons are targeted by different descending systems. i.e.  
phrenic motoneurons driving respiratory musculature obviously receive very 
different controls than motoneurons controlling the musculature of the lower 
extremities. This is an extreme case but it also applies for example to neck 
motoneurons, trunk motoneurons, upper extremity motoneurons, pelvic sphinter 
motoneurons. All these are spinal cord alpha motoneurons

Good luck in your studies.

Francsico J. Alvarez
Wright State University

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