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WVSOM -- Medical Neuroscience -- CBST

Where are cell bodies of the coritcobulbospinal tracts? cell bodies in the ventral horn
Where are cell bodies of flexors in comparison to the extensors? flexors have neurons in the lateral gray matter while neurons innvervating extensors are more medial
Where are neurons innervating distal muscles located compared to neurons more proximal muscles? neurons innervating distal muscles are more ventral than the neurons innervating more proximal muscles
What are the 4 tracts of descending motor pathways? Corticobulbospinal tract, rubospinal tract, reticulospinal tract and vestibulospinal tract
Where are cell bodies of the corticobulbospinal tract? cerebral cortex, mostly in pre-central gyrus
Where does the corticobulbal synapse happen? red nucleus, Reticular formation and CN III-VII, X-XII
Where do the fibers of the CBST converge? corona radiate and then travel in posterior limb and genu of the internal capsule
What part of the IC does the corticospinal travel ? Posterior Limb
What part of the IC does the corticobulbar travel? genu
What happens to the CBST in the pons? broken up into scattered fiber bundles in the basilar portion of the pons (ventral)
What happens to the CBST in the medulla? coalese into the medullary pyramids and nearly all cross the midline.
Where does the CBST cross over? pyramidal decussation of the medulla
Where do the crossed fibers travel? lateral Corticospinal tract
Where do the uncrossed fibers of the CBST travel? anterior Corticospinal tract
How much of the fibers do NOT cross over form the corticospinal tract? 10%
What does the lateral corticospinal tract contro? movement of exgtremities
What does the anterior corticospinal tract control? movement of axial muscles
What does injury or disease of the anterior horn cells or projecting axons result in? paralysis of muscles, loss of muscle tone, atrophy of denervated muscle, absent myotatic (deep tendon) reflexes
What are the lower motor neuron? ventral horn cells and their axons projecting via the ventral root to striated muscle
What are the upper motor neurons? neurons which are contained within the descending motor pathways and influence the alpha motor neuron
What are characterized by upper motor neuron lesions? paresis or paralysis of muscles involved, increased muscle tone, hyperactive myotatic reflexes, babinski sign
Why is muscle atrophy not initially seen with upper motor neuron lesions? because innervations of striated muscle remains intact. Long term diuse will finally cause atrophy
What is babinski sign? Fanning of the toes that causes extension of the big toe and fanning of the other toes. Normal in infants. Occurs because of damage to upper motor neurons
Describe the Corticospinal tract. Motor cortex travels down PLIC, thru crus cerebri in basilar pons, to pyramids in medula. Splits 90% cross to L. Corticospinal and 10% anterior cortico. Then synapse on muscle nuerons in dorsal horn.
Describe the Corticobulbar tract. Travel more medially in midbrain sill in crus cerebri and synapses in midbrain in red nucleus adn CN III/IV all ipsilateral. Travels in pons in CN V and then at pontumedullary junction at CN VII/VI then bilateral to X, contralateral to XII and XI
Created by: tjamrose