Lecture 10 - Spinal Cord, Brainstem, and Cortex Control of Motor Function II

Question 1

What is the pyramidal system and what are its components?

L10 S4

Answer 1

Formed by tracts that pass through the medullary pyramids.

Consists of:

• corticospinal tract
• corticobulbar tract

Originates in motor cortices.
Most decussate in pyramids to form lateral cotricospinal tract (all spinal levels) while the other decussate in the spinal cord to form anterior corticospinal tracts (primarily neck and upper limbs).

Question 2

What is the result of a corticospinal tract lesion?

L10 S18

Answer 2

Typically bilaterally

• reduced muscle tone
• clumsiness
• weakness
• not complete paralysis (unless accompanied by extrapyramidal lesion)

Question 4

What is the result of a corticobulbar tract lesion?

L10 S22

Answer 4

Typically unilateral

-mild muscle weakness

Hypoglossal nerve lesion:
-paralysis of ipsilateral side of tongue

Facial nerve lesions:
-paralysis of ipsilateral lower quarter of face

Question 5

What is the extrapyramidal system?

L10 S24

Answer 5

Pathways that don’t pass through the medullary pyramids and aren’t part of the corticobulbar tracts.

Consist of:

• rubrospinal tract
• vestibulospinal tract
• reticulospinal tract
• olivospinal tract

Question 6

What is the red nucleus?

L10 S26

Answer 6

Forms form corticocrubral pathway and corticospinal tract synapsing in magnocellular region.

Gives rise to rubrospinal tract.

Magnocellular region has somatotropin representation of all muscles in body (map)

Simulates flexors and inhibit extensors

Question 7

What is the rubrospinal tract?

L10 S28

Answer 7

Originates in red nucleus and decussate in midbrain.

Descends in lateral funiculus.

Responsible for large muscle movement and some fine UE movement.

Question 8

What is the result of a rubrospinal lesion?

L10 S29

Answer 8

• impairment of distal arm and hand movement

- intention tremors

Question 9

What is the vestibulospinal tract?

L10 S31

Answer 9

Originates it vestibular nucleus and descends ing anterior funiculus.

Receives input from CN VIII about position changes of the head.

Lateral tract:

• ipsilateral control
• important in upright posture specifically in trunk and LE

Question 10

What is the reticulospinal tract?

L10 S33

Answer 10

Originates in reticular formation and descend in anterior and lateral funiculus.

Mediates large movements of trunk or upper limbs.
Mediates autonomic functions.
Modulates pain.

Question 11

What are the different functions of the reticular nuclei?

L10 S35

Answer 11

Pontine reticular nuclei:

• makes up pontine reticulospinal tract (anterior)
• simulators effect of extensors and flexors (mostly extensors)

Medullary reticular nuclei:

• makes up medullary reticulospinal tract
• inhibitory effect on both extensors and flexors (mostly extensors)

Question 12

What are the components of the vestibular apparatus?

L10 S40

Answer 12

Utricle:

• macula (hair containing structure) located on horizontal plane
• detects head orientation when upright

Saccule:

• macula located on vertical surface
• detects head orientation when lying down

Semicircular canals

Question 13

What is the corticobulbar tract?

L10 S19

Answer 13

Upper motor neurons of cranial nerves that synapse in cranial nerve nuclei.