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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 principal regions of the midbrain are the tectum, the cerebral aqueduct, tegmentum, and the cerebral peduncles. Rostrally the midbrain adjoins the diencephalon (thalamus, hypothalamus, etc.), while caudally it adjoins the hindbrain (pons, medulla and cerebellum). [5] In the rostral direction, the midbrain noticeably splays laterally.
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 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.
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 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 .
Trochlear nerve nucleus: This is the fourth cranial nerve. Red nucleus: This is a motor nucleus that sends a descending tract to the lower motor neurons. Substantia nigra pars compacta: This is a concentration of neurons in the ventral portion of the midbrain that uses dopamine as its neurotransmitter and is involved in both motor function and ...
Anatomically, as the name suggests, the MLR is located in the mesencephalon (or midbrain), ventral to the inferior colliculus and near the cuneiform nucleus. [6] Although identifying the exact anatomical substrates of the MLR has been subject to considerable debate, the pedunculopontine nucleus (PPN), cuneiform nucleus, and midbrain ...