Motor II- Extrapyramidal Pathway

Question 1

where is the red nucleus located?

Answer 1

in the tegmentum of the midbrain

Question 2

where do the fibres of the rubrospinal tract decussate?

Answer 2

in the midbrain

Question 3

what are the 4 extrapyramidal pathways?

Answer 3

rubrospinal, reticulospinal, tectospinal, vestibulospinal

Question 4

after the rubrospinal tract decussates, where does it descend and project to?

Answer 4

descend near the lateral corticospinal tract in the lateral column of the spinal cord and project to interneurons at the level of the cervical spinal cord

Question 5

what does the rubrospinal tract do?

Answer 5

it is a flexor-biased tract meaning that it influences the tone of flexor muscles of the contralateral upper limb

Question 6

where does the rubrospinal tract receive its afferent input from?

Answer 6

the motor cortex

Question 7

where does the tectospinal tract originate?

Answer 7

superior colliculi

Question 8

where does the tectospinal tract decussate?

Answer 8

midbrain tegmentum

Question 9

after the tectospinal tract decussates, where does it descend and terminate at?

Answer 9

descends to the anterior funiculus (column) of the spinal cord to terminate on motoneurons in the cervical spinal cord

Question 10

where are the cell bodies of the neurons of the recticulospinal tract located?

Answer 10

caudal pontine and rostral medullary tegmentum reticular formation

Question 11

where does the recticulospinal tract get its afferent input from?

Answer 11

motor cortex, basal ganglia, cerebellum as well as tectospinal and vestibulospinal tracts

Question 12

where does the recticulospinal tract descend to?

Answer 12

descend mainly ipsilaterally (some bilaterally) to the anterior funiculus (medial motor system)

Question 13

what are the fibres of the recticulospinal tract composed of?

Answer 13

composed of large axons that serve as a fast acting tract to the spinal cord

Question 14

what are the 2 kinds of motor behaviours of the recticulospinal system?

Answer 14

locomotion and postural control

Question 15

what are the functions of the recticulospinal tract?

Answer 15

• it is essential for initiation of locomotion as it gets input from the basal ganglia
• it maintains upright body posture by innervating anti-gravity muscles (gets input from the vestibulospinal tract ‘to sense gravity’)
• it is primarily an extensor-biased tract
• it receives input from the corticospinal tract concerning intended movement, and from tectospinal tract to stabilise the body during fast (reflective) movements of the head
• it receives input from the cerebellum concerning the actual sensory (proprioceptive) input related to skeletal muscles

Question 16

what are the reflexes involved in the vestibular system?

Answer 16

vestibulo-ocular reflex, vestibulo-cervical reflex and vestibulospinal reflex

Question 17

what is the vestibulo-ocular reflex?

Answer 17

helps maintain fixation of the eyes on an object during head movement (e.g. you can fixate your eyes and read even if your head moves)

Question 18

what is the vestibulo-cervical reflex?

Answer 18

stabilises head position during movement

Question 19

what is the vestibulospinal reflex?

Answer 19

maintains upright position and posture (maintains muscle tone in extensor muscles = anti-gravity muscles)

Question 20

where is the medial vestibular nuclei located?

Answer 20

midbrain

Question 21

where is the lateral vestibular nuclei located?

Answer 21

at the junction between the pons and medulla

Question 22

what is the function of the medial vestibular nuclei?

Answer 22

it is concerned with vestibulo-ocular reflex via the medial longitudinal fasciculus, (MLF) and vestibulo-cervical reflex (via medial vestibulospinal tract)

Question 23

what is the function of the lateral vestibular nuclei?

Answer 23

give rise to lateral vestibulospinal tract and is concerned with vestibulospinal reflex

Question 24

what does the lateral vestibulospinal tract do?

Answer 24

generates muscle tone (tone active) in deep back and limb extensors in response to gravity (to maintain balance and stance). It responds to postural changes to compensate for tilts and movements of the body (uses input from the semicircular and visual system)

Question 25

is the lateral vestibulospinal tract ipsilateral or bilateral? and what does it innervate?

Answer 25

acts ipsilaterally and innervates all levels of the spinal cord

Question 26

what does the medial vestibulospinal tract do?

Answer 26

keeps the head upright and stabilises head position during movement (uses input from semicircular canal) and coordinate head movements with eye movements (uses input from the visual system)

Question 27

is the medial vestibulospinal tract ipsilateral or bilateral? and what does it innervate?

Answer 27

acts bilateral (partially crosses over) and is limited to cervical spinal segments

Question 28

what does the lateral motor pathways feed into and innervate?

Answer 28

feed into the lateral motoneuron pool and innervate the appendicular muscles

Question 29

what does the medial motor pathways feed into and innervate?

Answer 29

feed into the medial motoneuron pool and innervate axial muscles

Question 30

what are the lateral motor pathways?

Answer 30

lateral corticospinal and rubrospinal

Question 31

what are the medial motor pathways?

Answer 31

anterior corticospinal, recticulospinal, vestibulospinal and tectospinal

Question 32

all ascending pathways pass through the _____ of the brainstem.

Answer 32

tegmentum

Question 33

all extrapyramidal tracts descend through the _____ of the brainstem.

Answer 33

tegmentum

Question 34

the corticospinal tracts descend through the _____ of the brainstem.

Answer 34

base

Question 35

all brainstem nuclei (apart from pontine and tectal nuclei) are located in the _________ of the brainstem.

Answer 35

tegmentum