Systemic Neuroanatomy: Motor System Flashcards
5 parts of the motor system
pyramidal, extra-pyramidal, corticobulbar, cerebellum, basal ganglia
What are the cells of origin for the corticospinal system? Where do they synapse? What kind of motion?
origin: large pyramidal neurons in the primary motor cortex and secondary motor cortex.
mostly synapses on cervical interneurons, with some lumbrosacral LMNs and interneurons.
flexor bias that gives FINE MOTOR CONTROL.
What is the course of the corticospinal tract?
In the telencephalon, located in the corona radiata
in the diencephalong, found in the posterior limb of the internal capsule
in the midbrain, found in the cerebral peduncle
in the pons, found in the basis pontis
in the medulla, found in the pyraminds where it decussates
in the spinal cord, found in the lateral funiculus
ONE AXON
(corona radiata –>internal capsule –> cerebral peduncle –> basis pontis –> pyramids (decussation) –> lateral funiculus
What four UMN tracts synapse on LMN at all spinal levels?
rubrospinal, lateral vestiubulospinal, pontine reticulospinal, medullary reticulospinal
Origin for rubrospinal tract? input from where? course?
red nucleus
gets input from cerebral cortex and cerebellum
fibers exit the red ducleus, decussates, travels through brain stem and lateral funiculus, uses interneurons to synapse on spinal LMN
What does the rubrospinal tract do? What other systems are important for its function?
input fro cerebral cortex and cerebellum given to red nucleus
flexor bias; helps with pyramidal fine motor control
What happens if you mess with the cortex input to the red nucleus?
rubrospinal tract proble
flexion of upper extremeties and extension of lower extremities, aka decorticate posturing
Origin for the lateral vestublospinal tract? input from where? course?
origin: lateral vestibular nucleus
gets input from vestibular apparatus
descends ipsilaterally through brain stem and ventral funiculus and synapses directly on spinal LMNs
What does the lateral vestublospinal tract do? What other systems are important for its function?
Extensor bias
helps iwth antigravity tone and upright posture
inhibited by red nucleus
What happens if you have a lesion to the red nucleus?
red nucleus can’t inhibit vestibulospinal tract
you see uninhibited extension of all 4 limbs, aka decerebrate posturing
Origine for pontine reticulospinal tract? input from where? course?
origine: pontine reticular formation
input: spinoreticular sensory fibers
descends ipsilaterally through the brain stem and ventral funiculus
synapses on spinal LMNs.
What does the pontine reticulospinal tract do?
extensor bias
helps maintain extensor tone, esp. in response to noxious stimuli.
Origin for the medullary reticulospinal tract? input? course?
origin: medullary reticular formation
input: cortex
descends ipsilaterally through brain stem and ventral funiculus. synapses via interneurons on LMNs
What does the medullary reticulospinal tract do?
flexor bias. augments corticospinal and rubrospinal
Origin for medial vestibulospinal tract? input? course? function?
origin: medial vestibular nucleus
input from vestibular apparatus
descends ipsilaterally through brainstem and ventral funiculus to synapse on cervical LMNs
function: coordinate head and neck motion with vestibular input to maintain head position
What tracts synapse on cervical LMNs exclusively?
medial vestibulospinal tract and tectospinal tract
Origin of tectospinal tract? course?
origin: superior colliculus; some in inferiror colliculus
exit the colliculi, decussate immediately, descend in the medial-dorsal brain stem and ventral cervical spinal cord. synapse on LMNs via interneurons.
coordinate head and neck motion w visual (and some auditory) stimuli
Function of corticobulbar system
major UMN tract controlling brain stem LMNs
How do the corticobulbar and corticospinal tracts differ?
Corticobulbar:
- innervates brain stem, not spinal LMNs
- travels in the genu of internal capsule
- provides both ipsilateral and contralateral innervation to all brain stem LMNs with the exception of the lower half of the face. Lower half of the face receive ONLY contralateral UMN innervation.
What does contralateral lower facial weakness indicate?
lesions to corticobulbar system. upper facial strength should be normal becasue of the ipsilateral projection of the corticobulbar tract to the upper half of the face
What is pseudobulbar palsy?
bilateral cortical lesions of the corticobulbar tract. generalized facial and bulbar weakness with difficulty speaking and swallowing.
