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Association fibers are axons (nerve fibers) that connect cortical areas within the same cerebral hemisphere. [ 1 ] In human neuroanatomy, axons within the brain, can be categorized on the basis of their course and connections as association fibers, projection fibers , and commissural fibers . [ 1 ]
The human cerebellum is located at the base of the brain, with the large mass of the cerebrum above it, and the portion of the brainstem called the pons in front of it. It is separated from the overlying cerebrum by a layer of tough dura mater called the cerebellar tentorium; all of its connections with other parts of the brain travel through the pons.
Fibers of the posterior column, which transmit sensory and proprioceptive information, are located behind the pyramids on the medulla oblongata. The medullary pyramids contain motor fibers that are known as the corticobulbar and corticospinal tracts. The corticospinal tracts are on the anterior surface of the pyramids.
The pons is also called the pons Varolii ("bridge of Varolius"), after the Italian anatomist and surgeon Costanzo Varolio (1543–75). [1] This region of the brainstem includes neural pathways and tracts that conduct signals from the brain down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus .
The brainstem is very small, making up around only 2.6 percent of the brain's total weight. [3] It has the critical roles of regulating heart and respiratory function, helping to control heart rate and breathing rate. [4] It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves.
The descending upper fibers from the internal capsule continue on through the midbrain and are then seen as the fibers in the cerebral peduncles. [5] The corticopontine fibers are found in the outer and inner third of the cerebral peduncle, these are the cortical input to the pontine nuclei. [6]
The posterior fibers (called the postcommissural fornix) of each side continue through the hypothalamus to the mammillary bodies; then to the anterior nuclei of thalamus via the mammillothalamic tract. The anterior fibers (precommissural fornix) end at the septal nuclei of the basal forebrain and nucleus accumbens of each half of the brain.
An osteoclast (from Ancient Greek ὀστέον (osteon) ' bone ' and κλαστός (clastos) ' broken ') is a type of bone cell that breaks down bone tissue.This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton.