Lecture 10: Control of Motor Function II Flashcards
define pyramidal system
these are tracts that pass through the medullary pyramids
what are the components of the pyramidal system
corticospinal tract
corticobulbar tract
what is the origin of the corticospinal tract
primary motor cortex
premotor cortex
somatosensory area
what is the pathway of the corticospinal tract
Site of origin → internal capsule → medullary pyramids → X in lower medulla
(most fibers) → lateral columns of spinal cord (lateral corticospinal tract)
what is the lateral corticospinal tract made up of and what does is supply
fibers that have crossed in the medulla
supplies all levels of spinal cord
what is the anterior corticospinal tract made up of and what does is supply
made up of uncrossed fibers
supplies neck and upper limbs
what is the function of the corticospinal tract
adds speed and agility to conscious movements and provides a high degree of motor control
describe corticospinal tract lesions
reduced muscle tone
clumsiness
weakness
not complete paralysis
what are the characteristics of corticobulbar tract
innervates the head
most fibers terminate in reticular formation near cranial nerve nuclei
describe corticobulbar tract lesions
lesions are typically unilateral
result in mild muscle weakness
what are the components of the extrapyramidal system
rubrospinal tracts
vestibulospinal tracts
reticulospinal tracts
olivospinal tracts
what stimulates the red nucleus
stimulation of flexors
inhibition of extensors
what are the characteristics of the rubrospinal tract
originates in red nucleus
decussates in midbrain
descends in lateral funicular
function is closely related to cerebellar function
less important in human for motor control
responsible for large muscle movement
describe lesions of rubrospinal tract
impairment of distal arm and hand movement
intention tremors
may take over for injured corticospinal tract in some animals
describe vestibulospinal tract
originates in vestibular nuclei
goal of maintaining balance
receives input from vestibular nerve
descends in anterior funicular
describe the lateral vestibulospinal tract
major part
ipsilateral
upright posture and balance
describe the medial vestibulospinal tract
projects bilaterally
controls LMN of CN XI
describe the reticulospinal tract
originates in various regions of reticular formation
descends in anterior portion of lateral funicular
thought to mediate larger movements of trunk and limbs that do not require balance or fine movements of upper limbs
controls activity of both alpha and gamma motor neurons
can modulate pain information
what are the functions of the vestibular apparatus
reflex adjustments of head, eyes, and postural muscles
provides a stable visual image and steady posture
describe the macula in the utricle
located on a horizontal plane
plays role in determining orientation of head when head is upright
describe the macula in the saccule
located in a vertical plane
signals head orientation when person is laying down
what are statoconia
small calcium carbonate crystals that are embedded in the gelatinous layer that covers the macula
