Point 3











Dorsal Spinocerebellar Tract at T1So far we have discussed 3 types of fibers that comprise the dorsal root. The alpha-betas are associated with the dorsal column system (fasc. gracilis and fasc. cuneatus) while the deltas and Cs are associated with the anterolateral system (ALS). The alpha-betas are bigger than the deltas and Cs, but there are fibers in the dorsal root that are even bigger (12-20um in diameter) These are called 1a, 1b and II fibers. Since these fibers (whose cell bodies lie in the dorsal root ganglia) are big, guess which division of the dorsal root they use when entering the spinal cord???? Of course, the MEDIAL, along with the alpha-betas. Remember that the skinny ones lie laterally (ahh, that hurts!!) and the more rotund ones medially.

1a, 1b and II Fibers and Muscle SpindlesYou have heard in Physiology that 1a and II fibers convey information from muscle spindles, while 1b fibers carry information from Golgi tendon organs. As Dr. Moss mentioned, this information is utilized for reflexes. However, all of this information also ascends to the cerebellum (L., little brain) in order to participate in motor coordination. How does this information reach the cerebellum??