Upper Motor Neurons Flashcards
what are the two main subdivisions of upper motor neurons?
pyramidal
extrapyramidal
what does the corticospinal tract of the pyramidal system control?
complex and fine movements
some control facilitating limb flexion
where does the corticonuclear tract of the pyramidal system project?
to the brainstem
where does the corticonuclear tract originate?
motor cortex
what does the corticonuclear tract innervate in the midbrain?
motor nuclei of the oculomotor (III) and trochlear nerves (IV)
how much of the white matter of the spinal cord is corticospinal tracts in primates and carnivores?
20-30% in primates
10% in carnivores
what nuclei are considered part of the descending extrapyramidal system?
red nucleus (midbrain)
tectum (midbrain)
vestibular nuclei (pons and medulla)
reticular formation (pons and medulla)
what is the primary regulator of voluntary locomotor activity in many animals?
rubrospinal system
where does the rubrospinal tract originate from?
red nucleus in the midbrain
where does the medial tectospinal tract originate?
tectum: rostral and caudal colliculi
where does the medial tectospinal tract run through?
only through cervical spinal cord
what is the primary function of the medial tectospinal tract?
orient head and neck in response to visual and auditory stimuli
________________________________ is a bundle of bilateral fibers that connect nuclei involved with coordinating eye movement
medial longitudinal fasciculus (MLF)
where does the medial longitudinal fasciculus receive input from?
vestibular nuclei
cranial nerves III, IV, VI
what is the reticular formation?
indistinct group of cell bodies that are clustered in the core of the brainstem
what does the pontine reticular formation facilitate?
standing
what does the medullary reticular formation do?
suppresses standing
what is activity in the lateral vestibulospinal tract influenced by?
input from vestibular nuclei from the cerebellum
what is the lateral vestibulospinal tract important for?
maintaining posture
balance
what is the medial vestibulospinal tract important for?
visual orienting and righting reflexes
signs associated with damage to the cerebellum and basal nuclei are __________ impairments
motor
are there direct projections from the cerebellum to the lower motor neurons?
no
what does the cerebellum integrate information concerning?
limb and trunk position
muscle stretch
voluntary movements in process or planned
what is the basal nuclei?
set of nuclei in forebrain and midbrain important for initiating and modulating movement
what are the forebrain nuclei of the basal nuclei?
caudate and putamen (striatum)
nucleus accumbens
globus pallidus
where are the main upper motor neuron nuclei found in most quadrupeds?
brainstem
what do upper motor neurons do by regulating lower motor neurons in the spinal cord?
initiate and maintain voluntary movement
muscle tone for weight support
regulation of extensor muscle tone
partial inhibition triceps/patellar reflexes
in whom is the corticospinal tract of the pyramidal system better developed?
primates
what does the corticonuclear tract of the pyramidal system do?
voluntary control over cranial nerves
the corticospinal tract controls movement on the ________________ side
contralateral
how are motor neurons organized?
somatotopically
what does the corticonuclear tract innervate in the midbrain?
motor nuclei of the oculomotor (III) and trochlear nerves (IV)
what do extrapyramidal tracts regulate?
instinctive and rhythmical movement and posture
what is the primary regulator of voluntary locomotor activity in many animals?
rubrospinal system
what does the medial longitudinal fasciculus do?
coordinates eye movement
does the reticular formation form distinct nuclear groups?
no
where does the medial vestibulospinal tract descend to?
mid-thoracic cord
clinically, what is damage to the cerebellum or basal nuclei associated with?
motor impairments
what does the paravermis do?
regulates error correction in evolving movements
what does the vermis do?
regulates muscle tone for posture and locomotion
what is the substantia nigra?
contains dopamine containing cell bodies that project to striatum and play a critical role in movement
midbrain structure
what do the lateral hemispheres of the cerebellum do?
project to lateral nucleus, regulate fine/skilled movement
where does the corticospinal tract decussate?
level of caudal medulla
