Other Motor Pathways 1

Question 1

What are the motor pathways?

Answer 1

• Apart from the Corticobulbar and the Corticospinal tracts there are other descending pathways that influence motor activity
• These pathways arise from the brainstem
• Commonly described as extrapyramidal pathways
• Play a major role in coordinating subconscious motor activity

Rubrospinal

Lateral reticulospinal

Medial reticulospinal.

Lateral vestibulospinal

Medial vestibulospinal

Question 2

What are the flexor-biased pathways ?

Answer 2

Apart from the lateral corticospinal tract there are two other pathways that influence flexion:

1. Rubrospinal tract
2. Lateral reticulospinal tract

Question 3

What is the Rubrospinal tract?

Answer 3

• Tract arises from neurons in the red nucleus
• It has cortical input (Cortico-rubro-spinal pathway)
• The axons cross the midline in the midbrain and descend to the contralateral spinal cord (cervical level)
• Primary action is to facilitate flexion in the upper limbs.

•Ends by synapsing on alpha and gamma motor neurons
in the dorsal aspect of the ventral horn cells

Question 4

What is the medullary (lateral) reticulospinal tract?

Answer 4

• Fibers arise from magnocellular neurons located in the medial two thirds of medulla.
• The fibers (ipsilateral and contralateral) descend to all levels of the spinal cord
• Fibers end on interneurons that synapse on alpha and gamma motor neurons in the ventral horn
• Major function of this pathway is to powerfully suppresses extensor spinal reflex activity and facilitate contraction of flexors.