In article <32A1B252.7F4E at indigo.ie> John King <johnkate at indigo.ie> writes:
>From: John King <johnkate at indigo.ie>
>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
>involved?
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