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CBST
WVSOM -- Medical Neuroscience -- CBST
| Question | Answer |
|---|---|
| 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
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