upper motor vs. lower motor neurons

Question 1

What is role of upper motor neurons vis a vis lower motor neurons

Answer 1

they provide commands to lower motor neurons in the ventral horn of the spinal cord.

Question 2

How do upper motor neurons communicate with lower motor neurons?

Answer 2

their axons course down spinal cord in white matter tracts and synapse on LMNs in anterior horn of spinal chord or brain stem

Question 3

what are the differences in symptoms between lower and upper motor neuron injury?

Answer 3

LMN injury can occur with damage to peripheral nerves. Signs are flaccid paralysis of muscles, hypotonicity, loss of the stretch reflex.
UMN injury can occur from spinal cord damage or stroke in higher CNS regions. Signs are loss of voluntary movements, spasticity, rigor, and exaggerated/aberrant reflexes (babinski sign)

Question 4

reflexes upper motor neuron and lower motor neuron signs

Answer 4

UMN, normal or increased

LMN, decreased or absent

Question 5

atrophy UMN and LMN signs

Answer 5

UMN, late and mild (due to disuse)

LMN, rapid and severe (neurogenic)

Question 6

tone UMN and LMN signs

Answer 6

UMN normal or increased

LMN decreased or absent