dorsal nucleus of the vagus nerve

Examples of dorsal nucleus of the vagus nerve in the following topics:

• Vagus (X) Nerve

  • The vagus nerve, also known as the pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves.
  • Eighty to 90% of the nerve fibers in the vagus nerve are afferent (sensory) nerves that communicate the state of the viscera to the brain.
  • The vagus nerve includes axons that emerge from or converge onto four nuclei of the medulla.
  • The dorsal nucleus of vagus nerve: Sends parasympathetic output to the viscera, especially the intestines.
  • Afferent vagus nerve fibers that innervate the pharynx and back of the throat are responsible for the gag reflex.

• Trochlear (IV) Nerve

  • It is the only cranial nerve that exits from the dorsal aspect of the brainstem.
  • The nucleus of the trochlear nerve is located in the caudal mesencephalon beneath the cerebral aqueduct.
  • It is immediately below the nucleus of the oculomotor nerve (III) in the rostral mesencephalon.
  • The trochlear nucleus is unique in that its axons run dorsally and cross the midline before emerging from the brainstem—so a lesion of the trochlear nucleus affects the contralateral eye.
  • The unique features of the trochlear nerve, including its dorsal exit from the brainstem and its contralateral innervation, are seen in the primitive brains of sharks.

• Hypoglossal (XII) Nerve

  • The hypoglossal nerve (cranial nerve XII) controls the muscles of the tongue.
  • It passes behind the vagus nerve and between the internal carotid artery and internal jugular vein which lies on the carotid sheath.
  • It supplies motor fibers to all of the muscles of the tongue, with the exception of the palatoglossus muscle, which is innervated by the vagus nerve (cranial nerve X) or, according to some classifications, by fibers from the glossopharyngeal nerve (cranial nerve IX) that hitchhike within the vagus.
  • Progressive bulbar palsy is a neuromuscular atrophy associated with the combined lesions of the hypoglossal nucleus and the nucleus ambiguous, upon atrophy of the motor nerves of the pons and medulla.
  • Schematic image of the hypoglossal nerve and the structures it innervates.

• Branches of Spinal Nerves

  • The spinal nerves branch into the dorsal ramus, ventral ramus, the meningeal branches, and the rami communicantes.
  • The dorsal ramus: Contains nerves that serve the dorsal portions of the trunk carrying visceral motor, somatic motor, and sensory information to and from the skin and muscles of the back.
  • Some ventral rami merge with adjacent ventral rami to form a nerve plexus, a network of interconnecting nerves.
  • This diagram depicts the course and branches of a typical thoracic spinal nerve.
  • The posterior division (dorsal ramus) is labeled at the top right.

• Trigeminal (V) Nerve

  • The sensory function of the trigeminal nerve is to provide the tactile, motion, position, and pain sensations of the face and mouth.
  • The trigeminal nerve is the largest of the cranial nerves.
  • It is derived from the fact that each nerve, one on each side of the pons, has three major branches: the ophthalmic nerve (V1 in the illustration below), the maxillary nerve (V2), and the mandibular nerve (V3) .
  • The trigeminal ganglion is analogous to the dorsal root ganglia of the spinal cord, which contain the cell bodies of incoming sensory fibers from the rest of the body.
  • Motor fibers pass through the trigeminal ganglion on their way to peripheral muscles, but their cell bodies are located in the nucleus of the trigeminal nerve, deep within the pons.

• Somatic Sensory Pathways to the Cerebellum

  • It is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract.
  • The axon runs via the fila radicularia (nerve rootlets) to the dorsal horn of the gray matter.
  • This is in contrast with the dorsal spinocerebellar tract (C8 - L2/L3), which only has one unilateral axon that has its cell body in Clarke's nucleus (only at the level of C8 - L2/L3).
  • Proprioceptive information is taken to the spinal cord via central processes of the dorsal root ganglia (where first order neurons reside).
  • These central processes travel through the dorsal horn where they synapse with second order neurons of Clarke's nucleus.

• Sciatic Nerve Injury

  • Sciatica is a set of symptoms rather than a diagnosis for what is irritating the root of the nerve, causing the pain.
  • Sciatica is generally caused by the compression of lumbar nerves L3, L4 or L5, or sacral nerves S1, S2, or S3, or by compression of the sciatic nerve itself.
  • When sciatica is caused by compression of a dorsal nerve root (radix), it is considered a lumbar radiculopathy (or radiculitis when accompanied with an inflammatory response).
  • The intervertebral discs consist of an annulus fibrosus, which forms a ring surrounding the inner nucleus pulposus.
  • When there is a tear in the annulus fibrosus, the nucleus pulposus (pulp) may extrude through the tear and press against spinal nerves within the spinal cord, cauda equina, or exiting nerve roots, causing inflammation, numbness, or excruciating pain.

• Cephalic Phase

  • It results from the sight, smell, thought, or taste of food; and the greater the appetite, the more intense is the stimulation.
  • Neurogenic signals that initiate the cephalic phase of gastric secretion originate from the cerebral cortex, and in the appetite centers of the amygdala and hypothalamus.
  • They are transmitted through the dorsal motor nuclei of the vagi, and then through the vagus nerve to the stomach.
  • The cerebral cortex sends messages to hypothalamus, the medulla, and the parasympathetic nervous system via the vagus nerve, and to the stomach (gastric glands in walls of fundus and body of stomach).
  • Receptors send message to the medulla, and then back to the stomach via the vagus nerve.

• Brief Overview of Cranial Nerves

  • The peripheral nervous system has 12 pairs of cranial nerves that control much of the motor and sensory functions of the head and neck.
  • The olfactory nerve (I): This is instrumental for the sense of smell, it is one of the few nerves that are capable of regeneration.
  • The optic nerve (II): This nerve carries visual information from the retina of the eye to the brain.
  • The vagus nerve (X): This is responsible for many tasks, including heart rate, gastrointestinal peristalsis, sweating, and muscle movements in the mouth, including speech and keeping the larynx open for breathing.
  • One that may be helpful is: Old Opie Occasionally Tries Trigonometry And Feels Very Gloomy, Vague And Hypoactive.

• Accessory (XI) Nerve

  • The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.
  • The accessory nerve (cranial nerve XI) controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
  • In fact, most of the fibers of the nerve originate in neurons situated in the upper spinal cord.
  • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.
  • During neurological examinations, the function of the spinal accessory nerve is often measured by testing the range of motion and strength of the aforementioned muscles.