Descending Motor Tracts: Extrapyramidal System

Question 1

Where does the Rubrospinal Tract originate from?

Answer 1

Red Nucleus

Question 2

Where does the Rubrospinal Tract cross midline?

Answer 2

Tegmental decussation in midbrain

Question 3

Pathway of the Rubrospinal Tract

Answer 3

Red Nucleus –> Crosses midline at tegmental decussation in midbrain –> dorsolateral funiculus –> synapses on spinal motor neurons –> Terminates in cervical and thoracic spinal cord

Question 4

Where does the Rubrospinal Tract synapse?

Answer 4

Spinal motor neurons

Question 5

Where does the Rubrospinal Tract terminate?

Answer 5

Cervical and Thoracic spinal cord

Question 6

What are the overall effects of the Rubrospinal Tract?

Answer 6

Enhances flexor tone and inhibits extensor tone in the proximal muscles and upper body

Question 7

Where does the red nucleus receive input from in primitive vertebrates and amphibians?

Answer 7

Cerebellum

Question 8

Where does the red nucleus transmit information to in primitive vertebrates and amphibians?

Answer 8

Contralateral spinal cord

Question 9

What forms the Rubrospinal Tract in primitive vertebrates and amphibians?

Answer 9

Early magnocellular red nucleus neurons

Question 10

Describe the Rubrospinal Tract in Quadruped Reptiles

Answer 10

• Ipsilateral rubro-olivary projection emerges
• Contralateral olivary projection to cerebellum emerges
• Parvocellular red nucleus neurons forming early rubro-olivo-cerebellar tract
• Red nucleus relies on lateral nucleus for cerebellar information

Question 11

What is the purpose of the Rubro-Olivo-Cerebellar Pathway (ROCP)?

Answer 11

Test predictions of motor timing and motor accuracy

Question 12

Describe the Rubrospinal Tract in Quadruped Mammals

Answer 12

• Corticospinal tract begins to replace rubrospinal tract
• In red nucleus, magnocellular and parvocellular neurons become more distinct
• Cerebral cortex begins synapses on parvocellular neurons
• Red nucleus receives cerebellar information via lateral nucleus and interposed nucleus
• ROCP becomes more distinct

Question 13

Describe the Rubrospinal Tract in Primates

Answer 13

• Corticospinal tract replaces rubrospinal tract
• Clear boundaries between magnocellular neurons and parvocellular neurons -
• Cerebral cortex synapses separately on both parvocellular and magnocellular neurons
• Inputs to red nucleus become more distinct

Question 14

Where does the Lateral “Medullary” Reticulospinal Pathway originate?

Answer 14

Medullary reticular formation (in medulla)

Question 15

Does the Lateral “Medullary” Reticulospinal Pathway cross midline?

Answer 15

NO! Stays ipsilateral

Question 16

Where does the Lateral “Medullary” Reticulospinal Pathway pass down?

Answer 16

Lateral funiculus

Question 17

What is the purpose of the Lateral “Medullary” Reticulospinal Pathway?

Answer 17

Synapse on and activate inhibitory spinal motor interneurons

Inhibits gamma LMNs

Strongly inhibits extensor activity to help with flexor actively for the gait cycle

Question 18

True or False: The Lateral “Medullary” Reticulospinal Pathway supports overall extensor activity by primarily inhibiting flexors

Answer 18

False, The Lateral “Medullary” Reticulospinal Pathway supports overall flexor activity by primarily inhibiting extensors

Question 19

Where does the Ventral “Pontine” Reticulospinal Pathway originate?

Answer 19

Pontine reticular formation (in pons)

Question 20

Does the Ventral “Pontine” Reticulospinal Pathway cross midline?

Answer 20

NO! Stays ipsilateral

Question 21

Where does the Ventral “Pontine” Reticulospinal Pathway pass down?

Answer 21

Ventral funiculus

Question 22

What is the purpose of the Ventral “Pontine” Reticulospinal Pathway?

Answer 22

Synapse on and activate gamma LMNs

Facilitates extensor activity needed for the gait cycle

Question 23

True or False: The Ventral “Pontine” Reticulospinal Pathway supports overall extensor activity?

Answer 23

True

Question 24

Where does the Tectospinal Tract originate from?

Answer 24

Super colliculus

Question 25

Where does the Tectospinal Tract cross midline?

Answer 25

Dorsal tegmental decussation in midbrain

Question 26

Where does the Tectospinal Tract pass down?

Answer 26

Medial ventral funiculus

Question 27

What is the purpose of the Tectospinal Tract?

Answer 27

Helps generate coordinated movements of head and eyes in response to light and auditory stimuli Supports head and eye responses to light and sound

Question 28

What are the four types of Bilateral Vestibulospinal Nuclei?

Answer 28

Rostral Vestibular Nucleus Medial Vestibular Nucleus Lateral Vestibular Nucleus Caudal Vestibular Nucleus

Question 29

Where do the Bilateral Vestibulospinal Nuclei receive input from?

Answer 29

Vestibulocochlear Nerve (CN VIII)

Question 30

Where do the Bilateral Vestibulospinal Nuclei send output to?

Answer 30

Spinal cord, Brainstem, and Cerebellum

Question 31

What is the main central connection between CN III, CN IV, and CN VI

Answer 31

Medial longitudinal fasciculus

Question 32

What does the Medial longitudinal fasciculus do?

Answer 32

Connect each CN VI with its contralateral CN III for coordination of horizontal eye movements Contains fibers from vestibular nuclei to CN III, CN IV, and interstitial nucleus of Cajal for coordination of movement between head and eyes

Question 33

What is the medical term for double vision?

Answer 33

Diplopia

Question 34

Where does the Medial Vestibulospinal Tract originate from?

Answer 34

Medial/Rostral/Caudal Vestibular Nuclei

Question 35

Where does the Medial Vestibulospinal Tract bifurcate and how many branches cross midline?

Answer 35

Rostral Medulla; 1

Question 36

Where does the Medial Vestibulospinal Tract pass down?

Answer 36

Ventral funiculus

Question 37

Where does the Medial Vestibulospinal Tract synapse?

Answer 37

Spinal motor interneurons and possibly LMNs

Question 38

Where does the Medial Vestibulospinal Tract terminate?

Answer 38

Cervical and Cranial Thoracic Spinal Cord

Question 39

What does the Medial Vestibulospinal Tract do?

Answer 39

Enhances extensor ipsilaterally and inhibits extensors contralaterally

Question 40

What are the target muscles for the Medial Vestibulospinal Tract?

Answer 40

Ipsilateral extensor and inhibition of contralateral extensor muscles

Question 41

Where does the Lateral Vestibulospinal Tract originate from?

Answer 41

Lateral vestibular nucleus and pons

Question 42

Does the Lateral Vestibulospinal Tract cross midline?

Answer 42

NO!

Question 43

Where does the Lateral Vestibulospinal Tract pass down?

Answer 43

Ventral funiculus

Question 44

Where does the Lateral Vestibulospinal Tract synapse on?

Answer 44

Spinal motor neurons and possibly LMNs

Question 45

True or False: The Lateral Vestibulospinal Tract courses down the entire spinal cord

Answer 45

True

Question 46

What does the Lateral Vestibulospinal Tract do?

Answer 46

Enhances extensor ipsilaterally Inhibits flexor ipsilaterally

Question 47

What are the target muscles of the Lateral Vestibulospinal Tract?

Answer 47

Activates ipsilateral extensor and inhibition of ipsilateral flexor and inhibition of contralateral extensor