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The middle cerebellar peduncle is one of the three stem-like structures that connects the brain's cerebellum to the pons. It is also the largest of such structures. The middle cerebellar peduncle gets its "middle" prefix from its placement. It is located between the topmost peduncle, which is called the superior cerebellar peduncle, and the bottommost peduncle, which is referred to as the inferior cerebellar peduncle. The middle cerebellar peduncle is also known as the brachia pontis.
As part of the center of the nervous system known as the "little brain," the cerebellum is a distinct region located at the rear and bottom area of the brain. It is primary responsible for regulating the body's movement. The middle cerebellar peduncle receives a copy of the data used for motor control via its connection of the cerebellum to the pons. Located below the peduncles, the pons comprises the upper part of the brainstem.
The middle cerebellar peduncle is mainly composed of fibers derived from its site of origination, the pontine nuclei. Also called the griseum pontis, the pontine nuclei is the specific part of the pons that helps in regulating motor activity. From there, the middle peduncle crosses the midline of the pons' ventral part called the basilar pons. Then the stem-like structure comes out of the opposite side of the brainstem, curving along the pons' dorsal side referred to as the pontine tegmentum. The peduncle ends its course when it goes into the cerebellum.
There are three fasciculi, or bundles, into which the fibers of the middle cerebellar peduncle are organized. They are called the superior fasciculus, the inferior fasciculus and the deep fasciculus. Each fiber that composes the peduncle is centripetal, meaning that it transmits nerve impulses toward the brain.
The superior fasciculus is the topmost fiber bundle of the middle cerebellar peduncle. Originating from the pons' upper transverse fibers, the superior fasciculus is primarily dispensed to the small lobes of the cerebellar hemispheres. These are the two lateral lobes that comprise the cerebellum.
Traveling under the superior fasciculus is the inferior fasciculus. This particular bundle consists of the pons' lowest transverse fibers. It is dispersed to the cerebellum vermis that unites the hemispheres.
The pons' deep transverse fibers make up the deep fasciculus of the middle cerebellar peduncle. Part of it is covered by the two aforementioned fasciculi. The fibers of the deep fasciculus go to the upper front cerebellar lobes.