Pixelated Brain: Module 6, Section 5 - Input from the spinal cord

THE DORSAL SPINOCEREBELLAR TRACT (DSCT)

First order neurons associated with muscle spindles, Golgi tendon organs and touch and pressure receptors in the leg send fibers into the cord to terminate in Clarke's Nucleus. Since the nucleus is present only from Ti toL3, afferents from more caudal segments have to ascend in the cord to reach it. Second order neurons within the nucleus send their axons laterally to ascend near the surface of the cord in the posterior part of the lateral funiculus. This pathway sends information about position and movement of the leg to the intermediate zone of the ipsilateral hemisphere.

THE VENTRAL SPINOCEREBELLAR TRACT (VSCT)

Cells on the lateral surface of the anterior horn of the lumbar cord give rise to the ventral spinocerebellar tract. Because of their position, these are called spinal border cells. These second order neurons receive the same inputs as described above for the DSCT, but in addition they receive inputs from a wide variety of cutaneous receptors and from descending motor pathways - primarily, the pyramidal tract. Thus they are "aware" not only of leg position and movement, but also of the motor "commands" that have initiated the movement. The ascending route taken by VSCT is also remarkable, as shown in Figure 6-16. The axons cross the midline to ascend on the contralateral side of the cord and brainstem, then cross back and enter the ipsilateral cerebellar hemisphere traveling with the superior cerebellar peduncle.

MODULE 6 - SECTION 5 - INPUT from the SPINAL CORD The
	Figure 6-16 drbstcrd_4_1i.jpg
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	THE DORSAL SPINOCEREBELLAR TRACT (DSCT) First order neurons associated with muscle spindles, Golgi tendon organs and touch and pressure receptors in the leg send fibers into the cord to terminate in Clarke's Nucleus. Since the nucleus is present only from Ti toL3, afferents from more caudal segments have to ascend in the cord to reach it. Second order neurons within the nucleus send their axons laterally to ascend near the surface of the cord in the posterior part of the lateral funiculus. This pathway sends information about position and movement of the leg to the intermediate zone of the ipsilateral hemisphere. THE VENTRAL SPINOCEREBELLAR TRACT (VSCT) Cells on the lateral surface of the anterior horn of the lumbar cord give rise to the ventral spinocerebellar tract. Because of their position, these are called spinal border cells. These second order neurons receive the same inputs as described above for the DSCT, but in addition they receive inputs from a wide variety of cutaneous receptors and from descending motor pathways - primarily, the pyramidal tract. Thus they are "aware" not only of leg position and movement, but also of the motor "commands" that have initiated the movement. The ascending route taken by VSCT is also remarkable, as shown in Figure 6-16. The axons cross the midline to ascend on the contralateral side of the cord and brainstem, then cross back and enter the ipsilateral cerebellar hemisphere traveling with the superior cerebellar peduncle.
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	At this level the ascending dorsal and ventral spinocerebellar tracts are joined by the cuneocerebellar tract. This pathway conveys to the cerebellum the same sort of information from the arm that the DSCT conveys from the leg. Note that in this case the central process of the first order neuron enters the cervical cord and ascends in the lateral part of the posterior funiculus to synapse on second order neurons in the accessory cuneate nucleus. Figure 6-16 shows this but does not label the nucleus.
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	Fibers of the doral and ventral spinocerebellar tracts continue rostrally. Fibers of the cuneocerebellar tract have reached the level of the accessory cuneate nucleus and will synapse on second order neurons of the pathway within it.
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