Lesson 6: Motor Pathways Flashcards
What is a lower motor neuron? Where is its cell body?
An alpha motor neuron - cell body in the ventral horn of the spinal cord
What is an upper motor neuron? Where is its cell body?
From the cerebral cortex - where its cell body is, in the gray matter - all the way to the spinal cord
What does corticobulbar mean?
Cortex to the neck
Bulbar = structures around the head and neck
What does corticonuclear mean?
Cortex to the brainstem
Nuclear = the cranial nerve nuclei in the brainstem
What is ipsilateral backup?
Extra input from the cerebral cortex on the same side - occurs for some of the cranial nerve nuclei
What modality is the lateral corticospinal tract?
Voluntary movement
What is the pathway of information in the lateral corticospinal tract?
Primary motor neuron: in the primary motor cortex, with its cell body in the gray matter
It then travels in the brainstem - in the crus cerebri of the midbrain, and then in the pyramids to the open medulla
At the pyramidal decussation - 90% of fibres cross. At the appropriate spinal level, it synapses onto the alpha motor neurons, which then travel to their muscle. They then release acteylcholine into the neuromuscular junction, which innervates the muscle
Where is the pyramidal decussation?
It is in the junction between the closed medulla and the spinal cord
How does the anterior corticospinal pathway differ from the lateral corticospinal pathway?
It synapses at the spinal cord
What are the 4 symptoms of an upper motor neuron lesion? Why do these symptoms occur?
The lower motor neuron is extra responsive. Hyperreflexia, slow and limited muscle wasting, spastic paralysis, clonus
What is clonus?
Rapid reversal of the hyperactive stretch reflex, causing a bouncing movement
What causes cerebral palsy?
Upper motor neuron lesions
What is an example of a reflex that is present with UMNLs?
Babinski reflex - toe curling and foot splaying
What are the symptoms of lower motor neuron lesions? Why do these symptoms occur? What symptoms do not occur (2)?
Flaccid paralysis, hyporeflexia/areflexia, rapid and marked atrophy
No Babinski reflex or clonus
What is brown sequard?
When only one half of the spinal cord is damaged
