UMN & LMN Systems Flashcards
General information about UMN Systems:
- Dorsolateral System
- Ventromedial System
- Two distinct descending motor pathways
- Distinct functions
- Named based on where the descending fibers pass within the spinal cord
Where would you find the cell bodies of UMN?
In the CNS- CORTEX AND BRAINSTEM
Where are the LMN cell bodies?
Also in the CNS- SPINAL CORD (mostly)
Where do UMN terminate?
ONTO LMN- in the spinal cord
Where do LMN terminate?
Onto skeletal muscles!
What is the function of UMNs?
To initiate and direct voluntary activity of muscles
Maintain muscle tone for posture and balance
What motor system(s) do UPPER motor neurons utilize as they travel down the spinal cord?
BOTH dorsolateral and ventromedial
Corticospinal and RUBROspinal tracts are part of which motor system?
Dorsolateral Motor System (UMN)
Which muscles are more likely to be controlled by the Dorsolateral motor system?
Distal and Flexor muscles
What are the major functions of the Dorsolateral motor system?
Fractionated and precise distal limb movements
The reticulospinal, VESTIBULOspinal, and Tectospinal tracts are part of which motor system?
Ventromedial (UMN)
Which motor system is more likely to control proximal and extensor muscles?
Ventromedial (UMN)
What are the functions of the Ventromedial motor system?
Posture & Balance
Whole limb movements
What is the most important tract/pathway for the dorsolateral motor system that influences LMN in a specific way?
Rubrospinal Pathway (UMN)
Where are the cell bodies of the DLMS Rubrospinal Pathway located?
In the RED nucleus of the midbrain
What is the most important tract/pathway of the ventromedial motor system that influences LMN in a specific way?
Vestibulospinal Pathway (UMN)
Where are the cell bodies of the VMMS Vestibulospinal Pathway located?
Hindbrain- Lateral Vestibular Nucleus
What is responsible for recruiting FLEXOR systems during the initiation and swing phases of gait?
Rubrospinal Tract (DLMS)
What happens if axons of the DLMS Rubrospinal tract are damaged?
Decreased voluntary movements or paralysis in flexor systems CAUDAL to the site of damage
What is responsible for controlling EXTENSOR systems in the support phase of gait?
The Vestibulospinal Tract (VMMS)
What happens if axons of the VMMS Vestibulospinal Tract are damaged?
Decreased voluntary movements or paralysis in extensor systems CAUDAL to the site of damage
What are two things that would cause UMN and LMN signs to vary?
Location of lesion &
Severity of lesion
What is transverse myelopathy?
Figuring out where lesions are in the spinal cord
What kind of signs would you see if you had damage to the gray matter (inner) of the spinal cord?
LOWER motor neuron signs
