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They are structures at the front of the midbrain which arise from the ventral pons and contain the large ascending (sensory) and descending (motor) tracts that run to and from the cerebrum from the pons. Mainly, the three common areas that give rise to the cerebral peduncles are the cerebral cortex, the spinal cord and the cerebellum. [2]
The efferent pathways include the cerebellorubral, dentatothalamic, and fastigioreticular tracts. All of them emerge from the deep cerebellar nuclei; the cerebellorubral fibers from the globose nucleus and emboliform nucleus, the dentatothalamic fibers from the dentate nucleus, and the fastigioreticular fibers from the fastigial nucleus.
All the fibers from the corticopontine system terminate in the pontine nuclei.The fibers descend through the sublenticular and retrolenticular of internal capsule, then traverse the midbrain through the basis pedunculi (i.e. ventral part of cerebral peduncle) to reach the pontine nuclei and synapse with neurons that give rise to pontocerebellar fibers.
The cerebral peduncles each form a lobe ventrally of the tegmentum, on either side of the midline. Beyond the midbrain, between the lobes, is the interpeduncular fossa, which is a cistern filled with cerebrospinal fluid [citation needed]. The majority of each lobe constitutes the cerebral crus.
The superior cerebellar peduncle connects to the midbrain. It consists mainly of efferent fibers , the cerebellothalamic tract that runs from a cerebellar hemisphere to the contralateral thalamus , and the cerebellorubral tract that runs from a cerebellar hemisphere to the red nucleus .
The middle cerebellar peduncle is the largest of the three cerebellar peduncles. It connects the pons and cerebellum.It consists almost entirely of fibers passing from the pons to the cerebellum (fibrocerebellar fibers); the fibers arise from the pontine nuclei and decussate within the pons before entering the peduncle [1] to end in the contralateral cerebellar hemisphere.
The frontopontine fibers or frontopontine tract are corticopontine fibers projecting from the cortex of the frontal lobe to the pons. In the internal capsule, the fibers descend predominately in the anterior limb (but some also in the posterior limb), passing inferior to the thalamus to reach the mesencephalon (midbrain) where they descend in the medial portion of base of the cerebral peduncles.
The inferior cerebellar peduncle is formed by fibers of the restiform body that join with fibers from the much smaller juxtarestiform body. [1] The inferior cerebellar peduncle is the smallest of the three cerebellar peduncles.