Motor Systems Flashcards
When we speak of an upper motor neuron legion, we usually mean a problem with which tract?
Lateral CST
Lower motor neurons
Neurons in spinal cord/ brainstem which innervate skeletal muscle
Located in the ventral/anterior horns of the gray mater
Organization of lower motor neurons based on innervation
Medial- innervate axial muscles
Lateral- distal muscles
Neurons for extensors are located ventrally
Flexors are located dorsally
Motor Units associated with LMN’s
S-Units: Slow, for things you do all day long (Red muscle fibers)
FF-units- Fast and fatigable (White muscle fibers)
FR-units- Fast and Resistant to fatigue (White muscle fibers)
The ventral horn gets ______ as they’re more muscles to innervate
Fatter
As you go from S to FF, the anterior horn cell becomes…
Bigger and the amount of force which can be generated becomes larger.
Main descending pathway of interest for motor activity
Corticospinal tract (lateral)- all excitatory
Basic characteristics of the CST
CORTICALSPINAL TRACT
- There are many non-motor fibers which run through this tract– sensorimotor integration
- As a result, it has multiple origins
- Only 50% of their fibers come from motor cortex
Betz cells
Concentrated in CST and have some control of hand and leg movement– likely have a large role in walking.
Most of the anterior spinal tract descends in the…
Posterior limb of the internal capsule
Corticobulbar tract fibers are located where?
Genu of internal capsule
Legion in the posterior limb if internal capsule mostly affect what?
Those fibers going to body or limbs on OPPOSITE side of the body.
Corticalspinal tract from the pyramids become…
Lateral corticospinal tract
Corticospinal tract is generally responsible for…
Fine motor movements of our hand
The layers which control motor function ultimately…
Drive lower motor neurons
Primary motor cortex
Location where the motor fibers are concentrated– NOT where learning occurs.
Lesion of anterior horn cell will give…
Lower motor neuron syndrome.
Weakness, twitches, atrophy of muscles
Legion of upper motor neurons wills give
Upper motor neural syndrome
Often affiliated with a stroke
Causes spasticity and some atrophy (but no twitches and minimal weakness)
Issue in cerebellum, association cortex or basal ganglia would cause…
Motor problem but no weakness
Oculomotor, trochlear and abducens nuclei receive what type of innervation from corticobulbar neurons?
NO DIRECT INNERVATION
They’re controlled by other collections of neurons in the brainstem
Cranial nerve nuclei associated with upper motor neurons
XII, V (mostly to opposite side)
VII (some bilateral, some opposite)
IX, X (bilateral)
Cranial nerve VII and its crossing over pattern
Cut of VII will cause facial paralysis on one side– Bell’s palsy
Stroke in cerebrum— Upper face would be spared on both sides. Opposite lower face would be paralyzed.
