motor control Flashcards
what are important CNS regions from control of motor movement?
cerebral cortex, brainstem, spinal cord as well as basal nuclei and cerebellum
what is another name for the cortical motor system?
the pyramidal system
what is the cortical motor system/pyramidal system made up of?
axons whose nerve cell bodies are located in motor areas of the cortex
where are the cell bodies of the cortical motor system/pyramidal system located?
in the pyramidal cell layer of motor areas of the cortex
where do the axons of the cortical motor system leave the cortex?
through the caudal limb of the internal capsule
where do the axons of the cortical motor system/pyramidal system pass through the midbrain?
the middle 3/5 of the crus cerebri
what is the corticobulbar tract?
axons from neurons in the cortex that extend and synapse in the brainstem. these synapse on motor neurons of the cranial nerves
what is the corticospinal tract?
it is axons with cell bodies in the cortex that extend from the cortex, through the internal capsule, through the crus cerebri of the midbrain and through the pons and onto the ventral surface of the medulla as the pyramids. the fibers then pass dorsally and decussate to the contralateral side to descend into the dorsal part of the lateral funiculus as the lateral corticospinal tract
what is different about ungulates in where the corticospinal tract goes?
in ungulates, most of the fibers of the corticospinal tract end in the cervical cord an interneurons take impulses to the LMN.
where does the corticospinal tract end in carnivores:
50% in cervical cord, 20% in thoracic area, 30% below this area
where do the corticospinal fibers send collateral branches to?
basal nuclei, thalamus, reticular formation, brainstem nuclei
where do the fibers of the corticobulbar tracts travel?
with the corticospinal tracts in then they leave the main pathway via three major branches: peduncular branch to nuclei or cranial nerves III, IV, VI and pontine branchV and the rostral part of the nucleus ambiguus and a bulbopontine branch to the motor nuclei of VII, XII and the caudal part of nucleus ambiguus.
what brainstem nuclei project to the spinal cord?
vestibular nuclei (vestibulospinal tract) and numerous nuclei in the reticular formation of the pons and medulla (pontine and medullary reticulospinal tracts)
what is the brainstem responsible for (in terms of motor function?)
initiiating and coordinating actions for semiautomatic movements: locomotion, cheewing, maintaining muscle tone, posture
what are the basal nuclei?
group of nuclei in telencephalon, diencephalon, rostral midbrain that from subcortical feedback loop; receive input from cerebral cortex and provide input back to cortex
what are the 5 structures of the basal nuclei?
caudate nucleus, putamen, globus pallidus, subthalamuc nucleus, substantia nigra
what structures of the basal nuclei receive the input from the cortex?
the caudate nucleus and putamen
what are the caudate nucleus and putamen together referred to as?
the striatum
what are the fibers that goes from the cortex to the caudate nucleus and putamen called?
the corticostriate fibers
what are the major output fibers of the basal nculei?
substantia nigra and portions of globus pallidus that give feedback to cortex via the thalamus
do the basal nuclei have projections to the brainstem?
relatively few
do the basal nuclei have a direct influence on movement?
no that act through corticospinal and brainstem spinal projections
what are signs caused by lesions of CNS motor centers and pathways?
- paralysis or paresis
- local reflexes present but possibly altered
- appearance of abnormal reflexes
- disuse atrophy
what is the difference between the pyramidal and extrapyramidal systems?
the pyramidal system has to do with the neurons whose axons connect directly to motor neurons in the spinal cord. clinically, extrapyramidal system has to do with the basal nuclei
what are extrapyramidal signs of lesion?
involuntary movements or rigidity without paralysis
what are the three major regions which are directly involved in initiation of movement?
the spinal cord, brainstem and the cerebral cortex
what are the two important structures that regulate output from the brainstem and cerebral cortex
cerebellum and the basal nuclei
what distinguishes voluntary movements from reflexive movements?
voluntary movements they are purposeful and do not necessarily have to be evoked by external stimuli
why can lesions that disrupt the brainstem affect muscle tone?
they may disrupt the brainstem lesions such as the vestibular nuclei and nuclei of the pontine reticular formation as well as the red nucleus. these centres tend to facilitate postural muscles
