Nervous system...descending motor pathways?

Question

so, i need someone to verify what I'm saying and correct me, if need be. i'm learning this in french so some names will be french.

alpha motoneurones have their soma's in the "corne ventrale" of the spinal chord. They are located in the motor nuclei (noyaux moteurs) and control muscular contractions of distal and proximal extensor and flexsors.

The synapse of the following pathways with the alpha motorneurons gives the corresponding muscular outcome.
-proximal extensors (antigravity, posture, involontary movements) = vestibulospinal pathway, reticulospinal pathway
- distal flexsors (volontary) = crossed corticospinal pathway (90% decussation)

Is this correct?

Answer 1

Ok, let's take this step-by-step:

Yes, the alpha motorneurons are located in the ventral horn of the spinal cord -- and yes they do control most somatic muscular action

Yes, the vestibulospinal and reticulospinal pathways are primarily mediated by the proximal extensor muscles in the back and legs, achieving their main function of balance and reaction to change

Yes, distal somatic flexor muscles are terminally mediated by alpha motor neurons that receive corresponding innervation from upper motor neurons, 85-90% of which cross-over at the pyramidal decussation in the medulla.

So, yes, all of the facts you've listed are correct, as far as I can tell.

Answer 2

Descending Motor Pathways

Answer 3

Alpha (lower) motoneurons whose dendrites and cells lie in the anterior gray horns of the spinal cord constitute the final common path which all impulses to skeletal muscles must transverse. In other words, axons of anterior horn neurons (or lower motoneurons as they are called) are the only motor fibers terminating in skeletal muscle (extensors and flexors).

The axons of a great many neurons converge upon--that is, synapse with--each lower motoneuron. The synapse of the following pathways with the lower motoneurons gives the corresponding muscular outcome:
Increased muscle tone of the proximal extensors (anti-gravity, posture, voluntary movements) via facilitatory reticulospinal fiber pathways (impulses)
Decreased tone and reflex response of proximal flexors via facilitatory reticulospinal fiber pathways

Decreased muscle tone and reflex response of the distal flexors (voluntary) via inhibitory reticulospinal fiber pathways
Increased tone of the distal flexors via inhibitory reticulospinal fiber pathways