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A cranial nerve nucleus is a collection of neurons (gray matter) in the brain stem that is associated with one or more of the cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by the severing of nerve(s) they ...
Name Location Notes medial vestibular nucleus (dorsal or chief vestibular nucleus) : medulla (floor of fourth ventricle) : corresponding to the lower part of the area acustica in the rhomboid fossa; [citation needed] the caudal end of this nucleus is sometimes termed the descending or spinal vestibular nucleus.
Medulla oblongata, shown by a transverse section passing through the middle of the olive. (Lateral medullary syndrome can affect structures in upper left: #9=vagus nerve, #10=acoustic nucleus, #12=nucleus gracilis, #13=nucleus cuneatus, #14=head of posterior column and lower sensory root of trigeminal nerve and #19=Ligula.)
The hypoglossal nucleus is a cranial nerve nucleus, found within the medulla.Being a motor nucleus, it is close to the midline. In the open medulla, it is visible as what is known as the hypoglossal trigone, a raised area (medial to the vagal trigone) protruding slightly into the fourth ventricle.
The neurons in these two nuclei (the dorsal column nuclei) are second-order neurons. [6] Their axons cross over to the other side of the medulla and are now named as the internal arcuate fibers, that form the medial lemniscus on each side. This crossing over is known as the sensory decussation.
Both dorsal column nuclei contain synapses from afferent nerve fibers that have travelled in the spinal cord. [2] They then send on second-order neurons of the dorsal column–medial lemniscal pathway. Neurons of the dorsal column nuclei eventually reach the midbrain and the thalamus. [3] They send axons that form the internal arcuate fibers. [4]
The paramedian pontine reticular formation (PMPRF) is involved in coordinating horizontal conjugate eye movements and saccades. To do so, besides projecting to the ibsilateral abducens nucleus, the PMPRF projects fibers through the MLF to the contralateral oculomotor nucleus (specifically, those of its motor neurons that innervate the medial rectus muscle).
Neurons of the SN are notably functionally arranged roughly length-wise along the nucleus: gustatory neurons are situated rostrally (with afferents from the anterior part of the tongue and roof of oral cavity rostral-most, and those from the larynx and epiglottis more caudally placed); gastrointestinal, cardiovascular, respiratory neurons are situated more caudally.