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Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs.Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing.
The pathway then projects down into the posterior grey column of the spinal cord, inhibiting pain sensation transmission. Oculomotor nerve nucleus: This is the third cranial nerve 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.
The upper motor neurons of the corticobulbar tract synapse with interneurons or directly with the lower motor neurons located in the motor cranial nerve nuclei, namely oculomotor, trochlear, motor nucleus of the trigeminal nerve, abducens, facial nerve and accessory and in the nucleus ambiguus to the hypoglossal, vagus and accessory nerves. [6]
The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the medullary pyramids, which are part of the brainstem's medulla oblongata (also called "bulbar") region, and are primarily involved in carrying the motor function of the non-oculomotor cranial nerves, like muscles of the face, head and neck.
The spinal trigeminal nucleus is a nucleus in the medulla that receives information about deep/crude touch, pain, and temperature from the ipsilateral face. In addition to the trigeminal nerve (CN V), the facial (CN VII), glossopharyngeal (CN IX), and vagus nerves (CN X) also convey pain information from their areas to the spinal trigeminal nucleus. [1]
The fibres that form the spinal accessory nerve are formed by lower motor neurons located in the upper segments of the spinal cord. This cluster of neurons , called the spinal accessory nucleus , is located in the lateral aspect of the anterior horn of the spinal cord, and stretches from where the spinal cord begins (at the junction with the ...
It is the part of the brainstem situated between the midbrain and the medulla oblongata. [3] [4] The horizontal medullopontine sulcus demarcates the boundary between the pons and medulla oblongata on the ventral aspect of the brainstem, and the roots of cranial nerves VI/VII/VIII emerge from the brainstem along this groove. [5]
The cerebrospinal fibers, derived from the cells of the motor area of the cerebral cortex, [1] occupy the middle three-fifths of the base; they are continued partly to the nuclei of the motor cranial nerves, but mainly into the pyramids of the medulla oblongata.