| Wikipedia: Spinocerebellar tract |
| Brain: Spinocerebellar tract | ||
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| Spinocerebellar tract is #4, in blue at right. | ||
| Gray's | subject #185 761 | |
| NeuroNames | ancil-2137625602 | |
The spinocerebellar tract is a set of axonal fibers originating in the spinal cord and terminating in the ipsilateral cerebellum. This tract conveys information to the cerebellum about limb and joint position (proprioception).
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Origins of proprioceptive information
Proprioceptive information is obtained by Golgi tendon organs and muscle spindles.
- Golgi tendon organs consist of a fibrous capsule enclosing tendon fasciculi and bare nerve endings that respond to tension in the tendon by causing action potentials in 1β afferent neurons (relatively large, myelinated, quickly conducting).
- Muscle spindles fibers are complicated systems of tension monitoring within muscles which result in information being carried via 1α neurons (larger and faster than 1β) (from both nuclear bag fibers and nuclear chain fibers) and II neurons (solely from nuclear chain fibers).
All of these neurons are "first order" or "primary", are sensory (and thus have their cell bodies in the dorsal root ganglion) and pass through Rexed laminae layers I-VI of the dorsal horn, to form synapses with "second order" or "secondary" neurons in the layer just beneath the dorsal horn (layer VII)
Subdivisions of the tract
The tract is divided into:
| Division | Information | Limbs |
| dorsal (posterior) spinocerebellar tract | Information from muscle spindles | hind limbs |
| ventral (anterior) spinocerebellar tract | Information from golgi tendon organs | hind limbs |
| spinocuneocerebellar tract | Information from muscle spindles | forelimbs |
| rostral spinocerebellar tract | Information from golgi tendon organs | forelimbs |
Pathway for dorsal and posterior spinocuneocerebellar tracts
In the dorsal tract, the sensory neurons synapse in an area known as Clarke's nucleus or "Clarke's column".
This is a column of relay neuron cell bodies within the medial gray matter within the spinal cord in layer VII (just beneath the dorsal horn), specifically between T1-L1. These neurons then send axons up the spinal cord and form synapses in the accessory (lateral) cuneate nucleus, lateral to the cuneate nucleus in the medulla.
Below L1, relevant neurons pass into the fasciculus gracilis (usually associated with the dorsal column-medial lemniscal system) until L1 where they synapse with Clarke's nucleus (leading to considerable caudal enlargement).
From above T1, neurons enter the fasciculus cuneatus directly and again synapse with neurons in the accessory cuneate nucleus. This pathway is known as the spinocuneocerebellar tract.
The neurons in the accessory cuneate nucleus have axons leading to the ipsilateral cerebellum via the superior cerebellar peduncle.
Pathway for ventral and rostral spinocerebellar tracts
Some neurons of the ventral spinocerebellar tract instead form synapses with neurons in layer VII of L4-S3. Most of these fibres cross over to the contralateral lateral funiculus via the anterior white commissure and proceed up the spinal cord to synapse with neurons in the superior cerebellar peduncle. The fibres then often cross over again within the cerebellum to end on the ipsilateral side. For this reason the tract is sometimes termed the "double-crosser."
The Rostral Tract is similar but is uncrossed and enters the cerebellum through the inferior cerebellar peduncle.
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