upper motor neruons (motor system)

what is the role of upper motor neurons?

deliver movement information from the brain to the lower motor neurons in the brainstem or spinal cord

upper motor neurons

-project FROM the cortical and brainstem centers to lower motor and interneurons

-they provide ALL motor signals from the brain to the spinal cord

how are UMNs classified?

by whether they synapse:

medially, laterally or throughout ventral horn

what are medial upper motor neurons in charge of?

postural and gross movementswh

Postural and Gross Movements tracts

-reticulospinal tract

-medial vestibulospinal tract

-lateral vestibulospinal tract

-medial corticospinal tract

Selective Motor Control of Limb Movements tracts

-lateral corticospinal tract

Nonspecific UMNs tracts

-raphespinal tract

-cerulospinal tract

Control of Muscles in the Head, Larynx, Pharynx, and Sternocleidomastoid and Trapezius Muscles tracts

-corticobrainstem tracts

what cranial nerves are the corticobrainstem tracts in charge of?

CN 5, 7, 11, 12

corticobrainstem tracts:

-starts in motor area of cerebral cortex, then goes to cranial nerve nuclei in brainstem

-facilitate LMN by innervating the facial muscles

Nonspecific UMNs

*not specific to a movement

-”emotional motor system”

-influence the activity of interneurons and LMNs in the spinal cord

Ceruleospinal

O: Locus coeruleus in the brainstem (junction of midbrain and pons)

F: enhances activity of interneurons and motor neurons through the spinal cord

*releases norepinephrine

Raphespinal:

O: raphe nucleus in brainstem

F: enhances activity of interneurons and motor neurons through the spinal cord

*releases serotonin

Reticulospinal tract facilitates lower motor neurons to:

voluntary reach and gross grasp (NOT RELEASE)

Medial Vestibulospinal tract facilitates lower motor neurons to:

movement of the muscles of neck and back

Lateral Vestibulospinal tract facilitates lower motor neurons to:

neck

responds to destabilization over our base of support relative to gravity

Medial Corticospinal tract facilitates lower motor neurons to:

neck, shoulder, and trunk muscles