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

Question 1

What is the function of the corticospinal tract.

What are the different pathways and where do they go?

RL10 S17-18

Answer 1

Function:

• speed and agility to conscious movements
• high degree of motor control

Lateral corticospinal tract:

• passes through medullary pyramids
• decussates in medulla
• supplies all levels of the spinal cord

Anterior corticospinal tract:

• passes through medullary pyramids
• does not decussate in medulla, but near synapse with LMN
• only supplies neck and upper limbs

Question 2

What is the result of a corticospinal tract lesion?

RL10 S19

Answer 2

• not complete paralysis
• clumsiness
• weakness

Question 3

What is the corticobulbar tract?

RL10 S20

Answer 3

UMNs for the cranial nerves that innervate the face, head, and neck.

Question 4

What is the red nucleus and what is its function?

RL10 S21

Answer 4

Fibers from:

• corticorubral pathway
• corticospinal tract

Contains magnocellular region which contains somatotopic map of muscles.

Function:

• stimulation of flexors
• inhibition of extensors (antigravity)

Question 5

What is the vestibulospinal tract?

What is its function and components?

RL10 S22

Answer 5

Receives input from vestibular nerve (CN VIII).

Functions in maintaining balance.
Synapses with extensor muscles (antigravity).

Components:
-Macula of utricle:
—location on horizontal plane
—functions when upright
-Macula of saccule:
—located on vertical plane
—functions when lying down
-semicircular canals

Question 6

What are maculas and how do they function?

RL10 S23

Answer 6

Contains gelatinous layer with calcium carbonate crystals.

Gelatinous layer displaces hair cells during movement of the head to generate an action potential (CN VIII).