Medial reticulospinal tract

At a glance

English

Medial reticulospinal tract

Latin (TA2)

Tractus reticulospinalis medialis tractus

System

Nerve

Region

Whole body

Side

Single, on the midline

About the medial reticulospinal tract

The medial reticulospinal tract, also called the pontine reticulospinal tract, is one of the two outputs by which the brainstem reticular formation controls spinal motor activity. The reticular formation is a column of loosely grouped nuclei without sharp borders that runs through the central brainstem. Its medial columns, with their large neurons, send long axons both upwards and down into the cord.

The medial tract begins in the oral and caudal pontine reticular nuclei. Its fibres descend almost entirely on the same side and gather in the anterior funiculus of the spinal cord, near the medial longitudinal fasciculus and the vestibulospinal fibres. They run the whole length of the cord and end on interneurons of the medial intermediate grey matter and on motor neurons that serve the axial and proximal limb muscles, often on both sides through crossed interneurons.

The descending motor tracts can be sorted into two groups. The medial group, made up of the reticulospinal and vestibulospinal pathways, keeps the head and body steady and upright. The lateral group, the corticospinal and rubrospinal pathways, gives precise control of the limbs. Fine movement depends on both, since a skilled hand needs a stable trunk and shoulder behind it. Within the medial system the pontine tract mainly excites extensor, antigravity motor neurons, opposing the medullary tract, which tends to inhibit them. It also prepares posture before a voluntary movement and takes part in the rhythm of walking.

Because the pontine reticular formation receives relatively little cortical inhibition, damage above it can release its excitatory effect on extensors. This contributes to the extensor posturing that may follow severe brainstem injury and to the spastic extensor tone of the lower limbs after upper motor neuron lesions.

Course and supply

Supplies

Excites motor neurons of the trunk and proximal limb extensors, supporting posture against gravity and the preparation of movement.

Blood supply

Runs in the anterior funiculus, within the territory of the anterior spinal artery.