L17: Descending Pathways - A

Question 1

Describe hierarchical organization of the Descending Pathways?

Answer 1

Premotor Cortex
Motor Cortex
A) Indirect
B) Direct

Question 2

True or False: The basal ganglia and cerebellum are involved in parallel processing of motor system

Answer 2

True

Question 3

Descending pathways are made of numerous descending tracts, which ultimately terminate on a ____
A. UMN
B. LMN

Answer 3

B. LMN

Question 4

What is the origin of the descending pathways?

Answer 4

Cerebral cortices (pyramidal neurons of Layer V)

Question 5

What is another name for the descending pathways?

Answer 5

Corticofugal pathways

Question 6

True or False: The descending pathways are afferent projections from the cerebral cortex

Answer 6

False - the descending pathways are EFFERENT projections from the cerebral cortex

Question 7

True or False: Voluntary control of movement occurs via direct communication between cortical motor areas + LMN located either in ___ or ___

Answer 7

1) Motor nuclei - associated with CN in brain stem

2) Ventral horn of SC

Question 8

The pathways associated with the voluntary movement are also grouped under the definition ___ system

Answer 8

pyramidal

Question 9

Three features of the Voluntary Motor Control Pathways?

Answer 9

1) Monosynaptic
- pyramidal cell (cortex) => LMN

2) Fast and uninterrupted communication

3) End contralaterally

Question 10

The term pyramidal system is applied to the __ tracts together with the functionally equivalent ___ fibers

Answer 10

corticospinal; corticonucelar

Question 11

What are the function of the corticospinal and corticonuclear tracts?

Answer 11

Realization of fine movements

Question 12

Fibers of which tract originate from large pyramidal neurons in Layer V of M-I, as well as premotor cortex, supplementary motor cortex, primary somatosensory cortex, and parietal association cortex?

Answer 12

Corticospinal Tract

Question 13

What happens at the spinomedullary junction?

Answer 13

Fibers in the pyramid decussate and enter lateral funiculus to become lateral corticospinal tract

Question 14

What happens to the fibers that do not decussate at the spinomedullary junction (aka: remain ipsilateral)?

Answer 14

Enter ventral funiculus to become anterior corticospinal tract

Question 15

Where do the fibers of the corticospinal tract ultimately decussate at?

Answer 15

Anterior commisure of SC - synapse with contralateral LMN’s

Question 16

True or False: At the end, all fibers of the corticospinal tract end contralaterally

Answer 16

True

Question 17

_____: Located in the lateral funiculus, projects somatotopically to all levels of the spinal cord, and will terminate at the ventral horn of all levels of the spinal cord
A. Ventral Corticospinal Tract
B. Anterior Corticospinal Tract
C. Lateral Corticospinal Tract

Answer 17

C. Lateral Corticospinal Tract

Question 18

Main function of the Lateral Corticospinal Tract (LCST)?

Answer 18

Activate neurons in ventral horn (those that innervate distal musculature – neurons that innervate muscle of hands/fingers/feet/toes)

Question 19

____: consists of 10-15% of CST that does not decussate at pyramidal decussation
A. Ventral Corticospinal Tract
B. Lateral Corticospinal Tract

Answer 19

A. Ventral Corticospinal Tract

Question 20

True or False: In the ACST, fibers are ipsilateral until levels at which they terminate, where they then decussate in the anterior white commisure to gain contralateral ventral horn

Answer 20

True

Question 21

Function of ACST (ventral/anterior corticospinal tract)?

Answer 21

Mostly unknown
- Activates neurons in ventral horn that innervate axial musculature

Question 22

Fibers of the corticonuclear tract originate from which 5 areas?

Answer 22

1) Pyramidal neurons in Layer V of M-I
2) PMC
3) Supplementart motor cortex
4) S-I
5) Parietal Association Cortex

Question 23

Fibers of which tract will directly synapse with neurons located in the motor nuclei of the cranial nerves?
A. Rubrospinal Tract
B. Corticonuclear Tract
C. Corticospinal Tract

Answer 23

B. Corticonuclear Tract

Question 24

Some fibers of the Corticonuclear Tract terminate in the nuclei of the midbrain (CN __ and ___) while the rest descend in the ___

Answer 24

CN III, IV; pons

Question 25

Which of the fibers of the Corticonuclear Tract terminate in the pontine nuclei? A. CN III and IV B. CN V, VI, VII C. CN IX, X, XI, and XII

Answer 25

B. CN V, VI, VII

Question 26

Which projections of the Corticonuclear Tract are not bilateral? A. CN VII/CN XII B. CN V, VI, VII, C. CN III and IV

Answer 26

A. CN VII/CN XII

Question 27

Which four CN of the corticonuclear tract will have fibers that end in synapses located in the medullar nuclei?

Answer 27

CN IX, X, XI, and XII

Question 28

Which of the following has fibers that arise from neurons in the red nucleus in the midbrain? A. Rubrospinal tract B. Corticonuclear tract C. Corticospinal tract

Answer 28

A. Rubrospinal tract

Question 29

Where do fibers of the Rubrospinal Tract decussate? terminate?

Answer 29

Midbrain Terminate - LMN's in the ventral horn

Question 30

True or False: The red nucleus receives direct cortical inputs (corticorubral fibers) from the bilateral motor cortices

Answer 30

False - The red nucleus receives direct cortical inputs (corticorubral fibers) from the IPSILATERAL motor cortices

Question 31

What is the primary function of the rubrospinal tract?

Answer 31

1) Influences flexor musculature -- supplements CST

Question 32

What symptoms would you expect to see if one has a lesion of the CST (aka: severing the pyramid)?

Answer 32

Able to: walk, climb, and pick up food Unable to: perform fine dexterous movements w/digits

Question 33

True or False: Rubrospinal system may partially compensate for loss of CST

Answer 33

True

Question 34

Which two tracts arise from vestibular nuclei in the brainstem (terminate in ventral horn of SC) + are activate in response to vestibular stimulation?

Answer 34

Lateral vestibulospinal tracts Medial vestibulospinal tracts

Question 35

True or False: Vestibulospinal tracts are important mediators of postural adjustments and head movements

Answer 35

True

Question 36

Which two tracts arise from the reticular formation of the brainstem?

Answer 36

1) Lateral Reticulospinal Tract 2) Medial Reticulospinal Tract

Question 37

True or False: Both the Lateral/Medial Reticulospinal tracts innervates EXTENSOR muscles and projects to ALL spinal cord levels

Answer 37

True

Question 38

Which of the following Reticulospinal tracts have axons that descend BILATERALLY in the ventral funiculus? descend IPSILATERALLY in the ventral funiculus?

Answer 38

Bilaterally - LRST Ipsilaterally - MRST

Question 39

Where do neurons of the MRST originate? Where do neurons of the LRST originate?

Answer 39

Pontine reticular formation Medullary reticular formation

Question 40

Where is the Tectospinal Tract located? A. Ventral funiculus of cervical/thoracic spinal cord B. Ventral funiculus of cervical spinal cord C. Lateral funiculus of thoracic spinal cord D. Lateral funiculus of cervical/thoracic spinal cord

Answer 40

B. Ventral funiculus of the cervical spinal cord only!

Question 41

Where does the Tectospinal Tract (TST) originate?

Answer 41

Neurons in the SC (superior colliculus)

Question 42

Where do the fibers of the TST terminate in? A. Ventral funiculus B. Ventral horn C. Lateral funiculus D. Lateral horn

Answer 42

B. Ventral horn (of cervical spinal cord only!)

Question 43

Which tract functions in reflex control and coordination of head, neck, and eye movements in response to visual and auditory stimuli + voluntary motor commands? A. Reticulospinal Tract B. Vestibulospinal Tract C. Rubrospinal Tract D. Corticonuclear Tract E. Corticospinal Tract F. Tectospinal Tract

Answer 43

F. Tectospinal Tract

Question 44

Rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts in parallel to ____ tracts carry descending info from cerebral cortices to LMB A. Corticospinal B. Corticonuclear

Answer 44

A. Corticospinal B. Corticonuclear

Question 45

Corticospinal + Corticonuclear tract = _____ system Rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts = ____ system

Answer 45

pyramidal system extrapyramidal system

Question 46

True or False: The extrapyramidal system is a genetic term that reassumes the different structures of the CNS and neuronal circuits, which guarantees involuntary movements + their adjustments

Answer 46

True

Question 47

True or False: Reverberating circuits influences cerebral cortex and, thus, motor output

Answer 47

True

Question 48

Which four structures belong to the extrapyramidal system?

Answer 48

1 = cerebral cortex 2 = basal ganglia 3 = nuclei of thalamus 4 = nuclei of brain stem

Answer 49