Lecture 10: Control of Motor Function II

Question 1

define pyramidal system

Answer 1

these are tracts that pass through the medullary pyramids

Question 2

what are the components of the pyramidal system

Answer 2

corticospinal tract

corticobulbar tract

Question 3

what is the origin of the corticospinal tract

Answer 3

primary motor cortex
premotor cortex
somatosensory area

Question 4

what is the pathway of the corticospinal tract

Answer 4

Site of origin → internal capsule → medullary pyramids → X in lower medulla
(most fibers) → lateral columns of spinal cord (lateral corticospinal tract)

Question 5

what is the lateral corticospinal tract made up of and what does is supply

Answer 5

fibers that have crossed in the medulla

supplies all levels of spinal cord

Question 6

what is the anterior corticospinal tract made up of and what does is supply

Answer 6

made up of uncrossed fibers

supplies neck and upper limbs

Question 7

what is the function of the corticospinal tract

Answer 7

adds speed and agility to conscious movements and provides a high degree of motor control

Question 8

describe corticospinal tract lesions

Answer 8

reduced muscle tone
clumsiness
weakness
not complete paralysis

Question 9

what are the characteristics of corticobulbar tract

Answer 9

innervates the head

most fibers terminate in reticular formation near cranial nerve nuclei

Question 10

describe corticobulbar tract lesions

Answer 10

lesions are typically unilateral

result in mild muscle weakness

Question 11

what are the components of the extrapyramidal system

Answer 11

rubrospinal tracts
vestibulospinal tracts
reticulospinal tracts
olivospinal tracts

Question 12

what stimulates the red nucleus

Answer 12

stimulation of flexors

inhibition of extensors

Question 13

what are the characteristics of the rubrospinal tract

Answer 13

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

Question 14

describe lesions of rubrospinal tract

Answer 14

impairment of distal arm and hand movement
intention tremors
may take over for injured corticospinal tract in some animals

Question 15

describe vestibulospinal tract

Answer 15

originates in vestibular nuclei
goal of maintaining balance
receives input from vestibular nerve
descends in anterior funicular

Question 16

describe the lateral vestibulospinal tract

Answer 16

major part
ipsilateral
upright posture and balance

Question 17

describe the medial vestibulospinal tract

Answer 17

projects bilaterally

controls LMN of CN XI

Question 18

describe the reticulospinal tract

Answer 18

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

Question 19

what are the functions of the vestibular apparatus

Answer 19

reflex adjustments of head, eyes, and postural muscles

provides a stable visual image and steady posture

Question 20

describe the macula in the utricle

Answer 20

located on a horizontal plane

plays role in determining orientation of head when head is upright

Question 21

describe the macula in the saccule

Answer 21

located in a vertical plane

signals head orientation when person is laying down

Question 22

what are statoconia

Answer 22

small calcium carbonate crystals that are embedded in the gelatinous layer that covers the macula