L38 Organization of the Motor System Flashcards
What sends very coarse signals that need to be modulated by the Basal ganglia, cerebellum and sensory systems?
the cortex
what are the voluntary motor systems?
- corticospinal
- corticobulbar
- rubrospinal
- pontine/medial reticulospinal
- medullary/lateral reticulospinal
what are the involuntary motor systems?
- lateral vestibulospinal
- medial vestibulospinal
*No cortical control of these!
what are the motor sensory input systems?
- muscle spindles
- DCML
- ALS
what descending motor tracts make up the ventromedial pathways?
- pontine reticulospinal
- lateral reticulospinal
- medial vestibulospinal
what descending motor tracts make up the lateral pathways?
- medullary reticulospinal
- corticospinal
- rebrospinal
medial pathways are biased for?
extension/abductor
lateral pathways are biased for?
flexion/adduction
describe Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease)
- progressively weakens and wrecks LMN
- eventually wreck pyramidal tracts and precentral gyrus (primary motor area)
- death by respiratory arrest
- die within 3-5 years of dx
what do spinal cord diseases usually affect?
motor and somatosensory tracts in the white matter
but may also affect motor neurons of anterior horn and sensory neurons of the dorsal horn
what will an anterior spinal artery occulusion (infarction) compromise?
compromise =
- 2nd order motor neurons in ant. horn
- lateral corticospinal tract
- anterior corticospinal tract
- ALS - pain/temp
what will an anterior spinal artery occlusion (infarction) compromises eventually result in?
- spastic paraparesis
- paraplegia (ant. horn damage = LMN)
- bilateral loss of P and T (ALS)
- TVP intact
- urine retention
- sexual dysfunction
what is the most likely cause of central medullary syndrome?
syringomyelia
what are the symptoms of central medullary syndrome?
- segmented muscle atrophy (usually in hands or fingers)
- loss of T and P
define lower motor neurons?
motor neurons that communicate directly with somatic muscle
define upper motor neurons?
motor neurons arising form motor centers in the brain that communicate either directly with LMN or indirectly via local interneurons
what are pyramidal motor systems?
tracts formed by corticospinal fibers that form with the pyramids of the ventral medulla. (term used interchangebly with corticospinal tracts)
define paralysis
complete or almost complete loss of motor function due to a lesion of neurons or muscle
what does plegia mean?
paralysis
what does paresis mean?
subparalytic muscle weakness
what does hemiparesis mean?
partial paralysis of one side of the body
define prevalence?
of cases of a disease present in a population at a given time
define incidence?
of new cases of a disease occurring during a certain period
which motor systems are most clinically important?
coritcospinal and corticobulbar systems
where does the lateral corticospinal tract start
pyramidal cells (layer 5) of Brodmann’s area 4 (PreCG)
where does the corticobular tract start
pyramidal cells (layer 5) of Brodmann’s area 4 (PreCG)
where does the rubrospinal tract start
red nucleus (midbrain)
where does the lateral vestibulospinal tract start?
lateral vestibular nucleus (largely pontine)
where does the medial vestibulospinal tract start?
medial vestibular nucleus in pons and medulla
where does pontine/medial reticulospinal tract start?
oral and causal reticular nuclei in pons
where does medullary/ lateral reticulospinal tract start?
gigantocellular reticular nucleus in medulla
where do LMN come from?
spinal cord (contribute to spinal n.) brainstem (contribute to cranial n.)
what motor neurons undergo decussation?
UMN
this means many motor centers may control muscles either bilaterally or contralaterally
where do the cell bodies of lateral (flexion) motor neurons dwell?
dorsal portion of ventral horn
where do the cell bodies of the medial (extension) motor neurons dwell
ventral portion of ventral horn
