Reticulospinal tract

Anatomy

• Reticulospinal tract is a descending tract present in the white matter of the spinal cord, originating in the reticular formation
• It is part of the Extrapyramidal system.
• It consists of bundles of axons that carry information or orders from the reticular formation in the brainstem to the peripheral body parts.
• Reticulospinal tract is responsible primarily for locomotion and postural control.
• Reticulospinal tract is comprised of the
  • Medial (pontine) tract: Descends ipsilaterally in the anterior funiculus. Responsible for controlling axial and extensor motor neurons e.g enable extension of the legs to maintain postural support ; Stimulation of the midbrain locomotor centre can result patterned movements (e.g. stepping)
  • Lateral (medullary) tract: Descends bilaterally in the lateral funiculus. Responsible for flexor motor neurons ; Inhibits the medial reticulospinal tract and therefore extensor motor neurons enabling modulation of the stretch reflex

Functions

• Motor activity: The reticulospinal tract is one of the most important extra-pyramidal tracts for controlling the activity of lower motor neurons. Its fibers can inhibit or stimulate motor activity.

• Posture Maintenance
• Control of Autonomic Functions such as heart rate, circulation, breathing, respiratory rate
• Control of Sympathetic and Parasympathetic Outflow: (Sacral parasympathetic outflow)

• Locomotion: When generating movements in two sides of the body within humans, it results in reciprocal inhibition of the flexors and extensors.

Spastic paraplegia

As the lateral reticulospinal's is involved in inhibition, if this pathway is disrupted it can result in spasticity . In addition due to the lack of descending inhibition, the medial reticulospinal tract  would then maintain spasticity in the musculature.