Upper Motor Neurons Flashcards
Ideas (motivation and planning) arise in the
Frontal lobe
Motor planning(organization of the movement) arises in the
Premotor areas
Informtation about spatial relationships arises in the
Posterior parietal cortex (parietal association cortex)
Where somatosensory and visual information are integrated
Posterior parietal cortex (parietal association cortex)
Difficulty in using body part to perform complex voluntary actions
Apraxia
Caused by lesions in premotoror posterior parietal cortex
Apraxia
Tested by asking patients to do things such as grasp a pencil or button a shirt
Apraxia
Project to SC and brainstem α-motor neurons and interneurons in lamina VIII and IX
Descending pathways
There are two groups of descending pathways. What do the following innervate:
- ) Medial pathways
- ) Lateral Pathways
- ) Proximal motor neurons (proximal muscles)
2. ) Distal motor neurons (distal muscles)
Upper motor neurons descend from the
Cortex or brainstem
The primary pathwayfor goal-directed movements
Corticospinal Tract (Pyramidal Tract)
Only descending pathway to project directlyto α-motor neurons of distal muscles
Corticospinal Tract (Pyramidal Tract)
The Corticospinal Tract (Pyramidal Tract) is the only pathway for
Fine movements of the fingers
The motor cortex is organized
Somatotropically
Project directly to motor neurons in the motor cortex
Large Betz Cells
The corticospinal tract can be disrupted in many places. But a common site for stroke is in the
Internal Capsule (affects posterior limb)
Projects directly and indirectly to motor neurons and motor interneurons in the lateral ventral horn (to distal muscles)
Lateral Corticospinal Tract (LCST)
Projects bilaterally to motor neurons and interneurons in the medial ventral horn (to proximal and trunk muscles)
ACST
The corticospinal tracts contribute to both the
Lateral and medial motor systems
Located in lateral funiculus, near to motor neurons to extremities
Lateral Motor Systems
Located in ventral funiculus, close to trunk motor neurons for proximal muscles
Medial Motor Systems
Major pathway for voluntary movements of the limbs
Lateral Corticospinal Tract
The lateral corticospinal tract is the only pathway for
Fine finger movements
Voluntary motor weakness (distal > proximal) on one side of the body are the major deficits with
LCST lesions
What is a sign that suggests LCST lesion?
Babinski sign
Lesions above the spinal cord produce
Contralateral deficits
Lesions of the spinal cord produce symptoms on the
Same side as lesion
Are always BELOW the level of the lesion
Deficits
Elicited by stroking the lateral plantar surface (the sole) of the foot
-The same reflex is seen in babies before the corticospinal tract is myelinated
Babinski Tests (Extensor plantar response)
These brainstem centers are used for responding to stimuli or movement errors, and to control postures and tone
Midbrain centers, Pontine Centers, and Medullary Centers
Most brainstem pathways are located in the
Medial Motor Systems
Most brainstem pathways are in the medial motor systems. Some of them only project as far as the
Cervical Spinal Cord
Project mainly ipsilaterally (some bilateral) to medial α-motor neurons throughout the length of the spinal cord
Reticulospinal Tracts
Contribute to posture and gait-related movements
Reticulospinal Tracts
Generate feed forward preparatory muscle activation
-Contribute to muscle tone
Reticulospinal Tracts
An elaborate sensory system in the inner ear with specialized receptors that monitor head position, movement and acceleration
Vestibular System
Both pathways project to the medial ventral horn
Lateral and Medial Vestibulospinal Tracts
Projects ipsilaterally to medial LMNs to proximal muscles.
-Especially facilitates extensor muscles in response to deviations from stable balance and upright balance
Lateral Vestibulospinal Tract
The lateral Vestibulospinal tract projects to the
Entire Spinal Cord
Projects bilaterally to controls (restores) head position in response to accelerations
Medial Vestibulospinal Tract
The medial vestibulospinal tract projects only to the
Cervical Spinal Cord
Tonic Activity in the reticulospinal tract and vestibulospinal tract facilitate
Muscle tone
Originates in the superior colliculus and crosses in the midbrain
Tectospinal tract
The tectospinal tract is in the
Medial Motor System
Generates orienting movements of the head to visual or auditory stimuli. It also helps to coordinate the eyes and head
Tectospinal tract
Originates in the red nucleus of the midbrain
-Crosses in the midbrain
Rubrospinal Tract
Travels next to LCST in the spinal cord Only extends to the cervical spinal cord
Rubrospinal Tract
The rubrospinal tract facilitates
Flexor muscles more than extensor muscles
Initial shut-down of spinal circuits that lasts several days
Upper motor neuron lesions (UMNs)
The most extreme and long lasting UMN is
Spinal Shock (after spinal cord injury)
Occurs with severe hyper-reflexia: 5-7 Hz oscillation when the muscle is rapidly stretched and then held at a constant length
Clonus
UMN syndrome from right sided stroke will affect
Left side (Will see Babinski)
Velocity-dependent: less resistance to slow movement compared to fast
Hypertonia in UMN lesions
Initial resistance followed by inhibition of the muscle (possibly due to golgi-tendon response) seen in UMN lesions
Clasp-knife response
In lesions above brainstem, we see which type of posture?
Decorticate
Variations on the posturing depends on the level of brain damage. This can be seen in patients who are
Comatose
Spreading of movements: movement of one part of the body produces movements in other parts of the body. (they may mirror). You may see this in children, foot flexion, and hand flexion
UMN syndrome symptom
What is a positive sign for a UMN?
Hoffman’s sign
By holding the patient’s finger loosely and flicking the fingernail downward, it will cause the finger to rebound into extension, if the thumb flexes and adducts, it is a positive
Hoffman’s sign
Corticobulbar tract innervation is mostly
Bilateral
One exception is that the corticobulbar tract innervation is contralateral to
CNVII motor neurons to lower nucleus of VII
These CNVII motor neurons to lower nucleus of VII go to the
Lower face
Another exception is that that corticobulbar tract innervation is mostly contralateral to
CN XII
Lesions to one corticobulbar tract produce the following deficit
Paralysis to contralateral lower face and some paralysis to opposite tongue
From a bilateral standpoint, lesions to the corticobulbar tract produce
Dysphagia and Dysarthria
What is innervation to CN VII for the:
- ) Upper face
- ) Lower face
- ) Bilateral
2. ) Contralateral
What are four causes of Upper motor neuron syndrome?
Trauma, Stroke, MS, and ALS
At birth, is the motor system fully developed?
No
How many years does it take for complete myelination?
2
What are the three primitive resources present at birth?
Palmar grasp reflex, rooting reflex, and moro reflex
The primitive reflexes should disappear by
3-6 Months
A variety of non-progressive neurological disorders that appear in infancy or early childhood
Cerebral Palsy
Permanently affect body movement and muscle coordination
Cerebral Palsy
Ischemia at birth, hypoperfusion, trauma, and hemorrhage are all causes of
Cerebral palsy
75% of the time, cerebral palsy presents with
Hemiplegia, Diplegia, or Quadriplegia
15% of the time, cerebral palsy presents with
Ataxia