Subcortical Motor Pathways

Question 1

The corticospinal tract is known as the

Answer 1

pyramidal system

Question 2

The subcortical motor system is often called the

Answer 2

extrapyramidal system

Question 3

Subcortical motor system is presumed to be primitive and associated with…

Answer 3

quick, instinctive and crude movement (synergistic)

Question 4

Subcortical motor system basics

Answer 4

• Involuntary movement
• “Start” in nucleus in the brainstem
• Motor pathways synapse with and make sure of the same lower motor neuron pathways that are associated in the corticospinal tract

Question 5

What are the three subcortical motor pathways?

Answer 5

• Rubrospinal Tract
• Reticulospinal Tract
• Vestibulospinal Tract

Question 6

Rubrospinal Tract

Answer 6

• Begins in the Red Nucleus (Located in the brainstem; receives input from CB and motor cortex)
• Tract descends in the spinal cord as the Rubrospinal Tract
• Decussation occurs, unknown; therefore it has contralateral involvement (likely midbrain)
• Decends next to the lateral Corticospinal Tract
• Function: UE Flexor tone (and inhibition of extensors)
• Mediate some function after damage to the pyramidal (CST) system; EX: Monkey
• Major connections with CB; Involved with coordination with reach to grasp tasks (Arm and hand movements are coordinated seperately)

Question 7

Reticulospinal Tract

Answer 7

• Begins in Reticular Formation (Located in both pons and medulla)
• Function: Facilitates (or inhibits) postural muscles accommodate postural shifts
• Axons from the reticular formation descend through spinal cord as the Reticulospinal Tract (lateral and medial tracts) near the CST.
• Axons synapse on interneurons in the cord bilaterally., crossing location has not been established.

Question 8

Reticular Formation

Answer 8

• Loose network of cells that are located in both pons and medulla
• Has many inputs
• Besides motor function, involved in arousal and activity level of the central nervous system (Vestibular system involved here because position changes the arousal level)
• Major production areas for neuro chemicals
• Small area, wide-spread impacts
• Involved with horizontal gaze coordination

Question 9

Vestibulospinal Tracts

Answer 9

• Begins at the Vestibular Nucleus (located at the pontomedullary junction)
• Function: Regulate and maintain balance and postural orientations (input from vestibular and CB)
• From Vestibular Nucleus goes into three pathways
  – Medial Vestibulospinal Tract (Modifies head position; bilateral innervation)
  – Lateral Vestibulospinal Tract (Modies postual response; axial/thoracic muscles; unilateral innervation)
  – Extra Ocular Vestibular Pathway (Allows eyes to remain fixed on target when the head moves)

Question 10

Extra Ocular Vestibular Pathway

Answer 10

• Travels from Vestibular Nucleus to the Abducens Nucleus (Lateral Rectus)
• From Abducens Nucleus to Oculomotor Nucleus (Medial Rectus)
• Unilateral innervation
• Abnormalities: Damage to one nucleus, leads to eyes overshooting; Nystagmus

Question 11

Hierarchy of Subcortical Motor Systems

Answer 11

1. Corticospinal System
2. Rubrospinal System
3. Reticulospinal System

Question 12

When Rubrospinal System becomes the primary motor system, what will the patient present with?

Answer 12

• Reflexive flexion of the upper limbs accompanied by extension of the lower limbs
• Decorticate Posture

Question 13

When Reticulospinal System becomes the primary motor system, what will the patient present with?

Answer 13

• Reflexive extension of the Upper and Lower limbs
• Decerebrate Posture
• Patients don’t often survive this as it means damage above the medulla

Question 14

If you observe nystamus with a patient, what pathways could be damaged?

Answer 14

Multiple options. Just know something is wrong!