Chapter 10/Upper Motor Neuron Flashcards
What are the descending motor systems?
motor cortex
brainstem centers
What are the descending pathways?
medial upper motor neuron (UMN) tract
Lateral UMN tracts
Nonspecific UMN tracts
Medial UMN tract:
postural and gross movements
Lateral UMN tract:
fractionated movements and distal limb movements
What do neural centers include?
vestibular nuclei
reticular formation
superior colliculus
What is the reticular formation?
a network of neurons in the core of the brainstem
What are the tracts of the medial upper motor neuron (UMN) tracts?
medial vestibulospinal
lateral vestibulospinal
reticulospinal
medial corticospinal
Where is the medial vestibulospinal tract from?
brainstem
Where is the lateral vestibulospinal tract from?
brainstem
Where is the reticulospinal tract from?
brainstem
Where is the medial corticospinal tract from?
cerebral cortex
What does the medial vertibulospinal tract to?
concerning information about head movement and position from the vestibular systems and controls neck and upper back muscles
What does the lateral vestibulospinal tract do?
- Responds to gravity information from the vestibular apparatus
- facilitate LMN to extensors and inhibit LMN to flexor muscles (maintaining balance on moving vehicle)
What does the reticulospinal tract do?
- Facilitates bilateral LMN innervating postural and gross movement of muscles throughout the body
- engaged in anticipatory postural adjustments (getting ready for running while awaiting go signal)
What does the medial corticospinal tract do?
Has a direct connection from cerebral cortex to the spinal cord
- UMNs from this tract synapse with LMNs that control neck, shoulder and trunk muscles
Where does the medial corticospinal tract facilitate motor neurons to?
neck, shoulder and trunk muscles
Where does the reticulospinal tract facilitate motor neurons to?
bilateral postural muscles and gross limb movement muscles of entire body
Where does the lateral vestibulospinal tract facilitate motor neurons to?
postural muscles
Where does the medial vestibulospinal tract facilitate motor neurons to?
neck
What do motor cortices do?
plans and directs execution of voluntary or volitional somatic movement (pyramidal motor system)
Why are motor cortices pyramidal?
due to the fact that the pathway from the cortex to the spinal cord runs through medullary pyramids, also called “corticospinal tract”
What does the motor cortex include?
- primary motor cortex
2. supplementary motor area
Where is the primary motor cortex?
pre-central gyrus
What does the primary motor cortex do?
- governing execution of voluntary movements
Where is the supplementary motor area (SMA) and lateral premotor cortex?
- part of three long frontal gyri
- superior, middle and inferior frontal gyri
What does the supplementary motor area (SMA) and lateral premotor cortex do?
organize movement sequences and planning movements
What is fractionation?
ability to activate individual muscles independently of other muscles
- essential for ADLs
Fractionation is part of what tract?
lateral upper motor neuron tract
What happens without fractionation?
the fingers and thumb would act as a single unit, as they do when picking up a water bottle
What is the most important pathway for controlling voluntary movements?
lateral corticospinal tract (CST)
Where does the CST arise?
from motor cortex
Where do the axons project in the CST?
axons project downward to pass first through the internal capsule, cerebral peduncles, anterior pons, medullary pyramids and lateral spinal cord to synapse with LMNs that control fine movements
What percentage of CST cross midline?
88
What percentage of CST travel ipsilaterally?
10
What percentage of CST travel in the medial CST?
2
The lateal corticospinal tract projects?
mainly contralateral
The lateral corticospinal tract facilitates what?
fractionate movements of the distal limbs
The retrospinal tract projects?
contralateral upper limb
The retrospinal tracct facilitates what?
extend wrist and fingers
Where does the lateral corticospinal tract arise?
fibers arise in the primary motor, premotor and SMA
The the primary motor cortex, what is there an equivalent to?
somatotopy to cortical sensory representation
What does the corticobrainstem tract facilitate?
lower motor neurons innervating the facial, vocalizing, eating, and large superficial neck muscles
Where does the corticobrainstem arise?
fibers arise in the cerebral cortex, then project to the CN nuclei in the brainstem
What are the two descending tracts associated with non-specific UMN?
- ceruleospinal tract
2. raphespinal tract
When are both tracts of the non specific UMN tracts active?
during excessively limbic activities, hence being called part of the emotional motor system
Where is the origin of the cereulospinal tract?
locus coeruleus in the brainstem
What is the function of the cereulospinal tract?
enhances activity of interneurons and motor neurons throughout the spinal cord
What is the origin of the raphespinal tract?
raphe nucleus in the brainstem
What is the function of the raphespinal tract?
enhances activity of interneurons and motor neurons throughout the spinal cord
