LMN vs UMN

Question 1

what are lower motor neurons (LMN)

Answer 1

• comprised of the cell body and axon that form the final motor neurons (cranial and spinal nerves) that innervate the skeletal muscles

Question 2

what are upper motor neurons (UMN)

Answer 2

• originates in the cerebral cortex and brain stem with axons contributing to the corticospinal, rubrospinal, reticulospinal, tectospinal and vestibulospinal tracts
• the UMN is confined to the CNS and terminates on the LMN

Question 3

UMN are responsible for:

Answer 3

• the initiation of voluntary movements
• maintenance of muscle tone for support against gravity
• regulation of posture

Question 4

paralysis

Answer 4

a complete loss of voluntary motor ability

Question 5

paresis

Answer 5

• partial loss of voluntary motor ability
• characterized by an inability to fully support weight while walking or standing, and tremoring when trying to stand

Question 6

spastic paresis/paralysis

Answer 6

increased extensor tone to the limbs

Question 7

flaccid paresis/paralysis

Answer 7

decreased extensor tone to the limbs

Question 8

ataxia

Answer 8

incoordination; an inability to predict where a foot will land

Question 9

spinal/proprioceptive ataxia

Answer 9

• crossing over of the limbs
• increased stride length
• abduction or circumduction of a limb or limbs
• walking on the dorsum of the paw

Question 10

vestibular ataxia

Answer 10

loss of balance

Question 11

cerebellar ataxia

Answer 11

• dysmetria
• abnormal rate or range of a movement
• over-stepping or goose-stepping gait with a delayed onset of volunary motion which, when initated is exaggerated