LMN/UMN Study Guide

Basic Concepts

Lower Motor Neurons (LMN)

Upper Motor Neurons (UMN)

Exercises

1. Draw a diagram depicting the flow of information from the motor cortex to the lip muscle to produce the /b/ sound in the word "baby."

2. For each of the following sites of lesion, determine the most likely impact on movement. The first one is completed as an example.

Site of Lesion
Impact on Movement
Rationale
Right Motor Cortex Noticeable weakness of tongue and lower face on the left side. Upper face should be symmetrical The right motor cortext contains UMNs. Only CN VII (lower face) and CN XII (tongue) have contralateral UMN innervation. The other CNs should not be notably impaired because they get innervation from both hemispheres.
Left Vagus Nerve (Recurrent Laryngeal branch only)    
Left internal capsule    
Right Facial Nerve (all branches)    
Right Trigeminal Nerve    

3. Consider evalution of motor speech disorders to predict site of lesion. From the descriptions below, identify the most likely site(s) of lesion. If you can only "narrow it down," identify the additional information needed to more confidently make a diagnosis

Behavioral Characteristics
Likely Site of Lesion
Additional Info Needed
weakness & hypertonicity in muscles of right lower face and tongue    
weakness & hypotonicity of velum, pharynx, and larynx    
left side of mouth fails to move upon command, but has appropriate movement during laughter    

4. For each of the following muscle groups, identify the side of the body where the LMN and UMNs will be found

Muscle Group
LMN Location
UMN Location
Lips    
Tongue    
Jaw    
Velum    
Larynx