Motor Neurons & Wiring Principles

Question 0

Functions of LMN

Slower signaling uses ___ to maintain health of muscle.

Damage to LMN eventually causes

Answer 0

“trophic factors”

atrophy & resting membrane instability (fasciculation (clinical finding) & fibrillations (electrophysiological finding)

Question 1

____ is the final pathway for all motor signals

Answer 1

LMN

Rapid signaling uses ACh as neurotransmitter to produce muscle movement - damage causes weakness

Question 2

What are the types of inputs to the LMN?

Answer 2

Sensory - monosynaptic (DTRs) & polysynaptic (various complex, testing for spasticity & eliciting Babinski)

UMN - monosynaptic (important but minority) & polysynaptic

Question 3

What is spasticity?

Answer 3

arm/leg is rigid; a lot of resistance when trying to stretch it - found in stroke patients

Question 4

What clinical signs differentiate UMN vs. LMN lesions?

Answer 4

UMN - weakness, hyper-reflexia, spasticity (increased tone), Babinski sign

LMN - weakness, hyporeflexia, flaccidity, atrophy