Spinocerebellar tracts

Spinocerebellar tractsAnatomy and function of the proprioceptive tracts
~ 4 min

In this note, we will continue discussing the anatomy and function of the tracts of the brain and spinal cord.

Let’s look at the spinocerebellar tracts:

  • Anterior
Anterior spinocerebellar tract
Anterior spinocerebellar tract
  • Posterior
Posterior spinocerebellar tract
Posterior spinocerebellar tract
  • and the so-called cuneocerebellar.

They represent the ascending pathways and carry sensory (afferent) information from peripheral receptors to the structures of the central nervous system for further processing.

Let’s start by defining the function.

These tracts carry information from proprioceptors (in particular the Golgi tendon organs and muscle spindles) and from some exteroceptors about the position of body parts to the cerebellum.

This sensation allows us to subconsciously control the position of muscles, tendons, and joints in space, providing movement coordination and maintenance of posture.

The spinocerebellar tracts have first- and second-order neurons.

Let’s discuss the posterior spinocerebellar tract: fibers from receptors are directed to the spinal ganglion, where they synapse with the first-order neuron of this pathway.

Spinal ganglion
Spinal ganglion

Then, the fibers enter directly into the spinal cord via the dorsal root, into the posterior horn.

Posterior horn
Posterior horn

The posterior thoracic nucleus also known as the dorsal nucleus of Clarke, which contains the second-order neuron of this pathway, is located in the spinal cord segments from C8 to L2/L3.

Posterior thoracic nucleus
Posterior thoracic nucleus

After this, the fibers ascend in the lateral funiculus of the spinal cord,

Lateral funiculus
Lateral funiculus

pass through the inferior cerebellar peduncle, and terminate in the anterior and posterior parts of the vermal cortex.

Inferior cerebellar peduncle
Inferior cerebellar peduncle

Since the posterior thoracic nucleus is absent in the cervical region of the spinal cord, the posterior spinocerebellar tract carries proprioceptive information only from the lower limbs and trunk.

In this regard, it is necessary to recall the anatomy of the dorsal column–medial lemniscus pathway.

Some fibers of the cuneate fasciculus

Cuneate fasciculus
Cuneate fasciculus

in the medulla oblongata synapse with the second-order neuron not in the cuneate nucleus but in the so-called accessory cuneate nucleus. The posterior external arcuate fibers then arise from it and form the cuneocerebellar tract, which travels toward the inferior cerebellar peduncle.

Posterior external arcuate fibers
Posterior external arcuate fibers

The cells of the accessory cuneate nucleus and the posterior thoracic nucleus are similar in their structure, so it can be said that the cuneocerebellar tract is an analog of the posterior spinocerebellar tract, but for the upper limbs.

Eventually, both tracts form a network of so-called mossy fibers that terminate in the cerebellar cortex.

Cerebellar cortex
Cerebellar cortex

Let’s examine the anterior spinocerebellar tract.

Fibers from receptors are directed to the spinal ganglion, where they synapse with the first-order neuron.

The second-order neuron is also located in the posterior horn of the spinal cord, but below the level of L2/L3.

After synapsing, the pathway crosses over to the opposite side (decussates) into the lateral funiculus, specifically into its more anterior sections.

It then ascends to the level of the upper pons, decussates back to the side of the receptors through the superior cerebellar peduncle, and terminates in the anterior part of the vermal cortex.

Superior cerebellar peduncle
Superior cerebellar peduncle

Spinocerebellar tracts

anterior spinocerebellar tract
tractus spinocerebellaris anterior
posterior spinocerebellar tract
tractus spinocerebellaris posterior
cuneocerebellar tract
tractus cuneocerebellaris
spinal ganglion
ganglion spinale
posterior horn
cornu posterius
posterior thoracic nucleus
nucleus thoracicus posterior
lateral funiculus
funiculus lateralis
inferior cerebellar peduncle
pedunculus cerebellaris inferior
vermis cortex
cortex vermis
cuneate fasciculus
funiculus cuneatus
accessory cuneate nucleus
nucleus cuneatus accessorius
posterior external arcuate fibers
fibrae arcuatae externae posteriores
superior cerebellar peduncle
pedunculus cerebellaris superior
cerebellar cortex
cortex cerebelli
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