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The Vagus Nerve and Its Home, the Nervous System Viva La Vagus!

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The Vagus Nerve and Its Home, the Nervous System Viva La Vagus! Viva La Vagus! by Miriam van Mersbergen Lights, music, excitement: that is what We have ample evidence that voice ceived reality (e.g. sight and hearing).6 Las Vegas has to offer. The bustle of the training provides excellent protection The basic unit in the nervous system Vegas Strip dazzles and amazes. In all the from injury and harm and have begun is called a nerve. Its main function is to drama of that city, however, little atten- to develop sophisticated motor theories communicate.7 Nerves contain three tion is given to the electricity that lights especially for voice production.2 Our basic parts: a cell body called a soma, it up. When one thinks of Las Vegas, they multi-disciplinary perspective of voice dendrites that carry information from may conjure many images, but probably science frequently takes for granted the other structures (other nerves, glands, none will be of the power cords that nerve that supplies the vocal folds with muscles, etc . .) to the soma, and axons, make that city run. power and gives them life. which carry information away from the Similarly, when we wax eloquent or soma to the next structure.8 The relay transcend through singing, we rarely of messages along these nerves can give thought to the power cord mak- The Vagus Nerve and its Home, be simple as a refl ex.9 However, nerve ing all of our efforts possible. Over the the Nervous System communication is often much more past fi fty years we have developed rich The nervous system is the commu- complicated, involving many nerves voice training traditions, sophisticated nication network of our body. It sends to and from the brain in an elaborate theories of voice production, and a commands for us to move, breathe, bucket brigade of signals.10 comprehensive understanding of laryn- digest, pump blood, secrete hormones Nerves communicate with each geal health. We have come a long way and chemicals, regenerate, feel, and other by way of electrical signals gener- in appreciating the unique nature of the even think.3 It is divided into the Cen- ated in the soma and traveling down tissues of the vocal folds and protecting tral Nervous System (CNS) and the the axon to an end point.11 At this end their delicate but strong vibrating edge.1 Peripheral Nervous System (PNS).4 point the electrical signal releases a The CNS houses the brain and spinal chemical into the space between the cord, and the PNS is comprised of the axon and the next structure (usually nerves that go out to the muscles, soft another nerve but sometimes a muscle Miriam van Mersbergen is ___________ tissues, glands, and organs of the body.5 or gland).12 Depending on the chemical, Professor of __________ and Director The PNS helps maintain homeostasis, the next structure is either activated or of _____________ at Northern Illinois shuts down. Subsequent sets of electri- University. encourage metabolism, control muscles, Email address ……………… release glandular secretions, and decode cal signals travel along dendrites into the environmental phenomena into per- soma of the next nerve.13 This form of CHORAL JOURNAL Volume 55 Number 3 61 electrical communication continues until and down through the thoracic cavity the larynx into the thorax and abdomen the system completes is function. to the abdomen.16 Vagus, the Latin for and assist in the regulation of the organs, Most peripheral nerves travel in bun- “wandering,” appropriately refl ects the glands, and soft tissue of these regions.20 dles, similar to electrical wires, and exit nerve’s meandering pathways.17 The vagus nerve carries messages the CNS from the spinal cord. How- Leaving the brain stem, the vagus from the CNS to the body (efferent/ ever, twelve peripheral nerves, called nerve branches off in different direc- motor) and relays messages to the CNS Cranial Nerves, exit the brainstem. They tions and extends as far down as the from the body (afferent/sensory).21 The regulate the muscles, glands, and sensory abdomen.18 Many of these branches are cell bodies of this nerve are housed in organs of the head and neck and are named according to their function, such four large areas in the brain stem, creat- identifi ed by Roman Numerals.14 Cranial as the auricular branch, which conveys ing a hub where nerves from different Nerve X, the largest of these nerves, is sensory information from the skin inside parts of the body communicate with called Vagus Nerve.15 Beginning in the the external ear canal and tympanic each other.22 The proximity of nerve cell brainstem, the nerve travels through membrane, and the laryngeal branch, bodies in this area allow various parts of the jugular foramen (the large hole at which innervates the larynx.19 Most the body to communicate complicated the bottom of the skull), into the neck, branches of the vagus travel far below information with each other, allowing for sophisticated processing of information. The Vagus Nerve and Voice Production Three branches of the vagus nerve are involved in voice production: the pharyngeal branch, the recurrent laryn- geal branch, and the superior laryngeal Let your music branch.23 When the pharyngeal branch leaves the brainstem and deviates, it be heard… travels to the mucous membranes and muscles of the pharynx, carrying sensory in England! information from this area to the brain.24 When you have a throat infection, for example, the vagus nerve carries the “This is one of the best groups information that lets you know your that I have had. Performance throat is sore. The pharyngeal branch venues were excellent. Witte also innervates most of the muscles of GLGDQRWKHUPDJQLÀFHQWMRE the pharynx and allows the palate to in making all aspects of our lift, maximizing the resonating space in concert tour run smoothly. our throat and creating those rounded tones we desire. They are the best!” The recurrent laryngeal branch – Phillip McLendon, Director leaves the larger laryngeal branch and Santa Barbara High School terminates in the larynx. It is called re- Madrigal Singers England and France, 2013 current because it travels past the larynx into the thorax and loops up into the larynx from below. On the right side, Witte has been arranging exceptional the nerve travels around the subclavian concert tours through England 800 GO WITTE wittept.com artery (right below the right clavicle), and the rest of the world since 1975. circling back into the larynx. The left side 62 CHORAL JOURNAL Volume 55 Number 3 travels further, winding around the aorta sided recurrent laryngeal nerve travels before returning back to the larynx.25 around the aorta. So, injuries on the The implications of right and left differ- left-side can be seen often in cardiac sur- ences will be discussed later. The recur- geries when the surgeon has to stretch rent laryngeal nerve innervates most of the nerve to retract it or to gain access 33 the muscles in the larynx, particularly to the heart. Sometimes the nerve is the muscles responsible for opening severed during tumor removal. At times and closing the vocal folds, which is viral infections reside in the cell bodies necessary for voicing.26 This nerve also of the recurrent laryngeal nerve, causing 34 innervates some of the muscles of the damage to nerve functioning. lower pharynx and esophagus to assist Recovery from recurrent laryngeal in swallowing. It transmits sensory in- nerve injury is directly related to the 36 formation from the mucous membrane degree and extent of the damage. of the upper trachea right below the Damage from a mild stretch or com- vocal folds.27 pression of the nerve may resolve The superior laryngeal nerve also quickly, and normal voicing may return exits the larger laryngeal branch, split- within a few months. When damage is ting off into two smaller branches.28 The considerable, however, recovery might intrinsic branch, which carries sensory not be complete and normal functioning information about the mucous mem- my never return, rendering an impaired 37 branes of the larynx, is active in provid- voice. Treatment for larger nerve in- ing information during a cough response. juries includes surgical procedures that The extrinsic branch innervates the can assist in vocal fold closure, therapy cricothyroid muscle, a laryngeal muscle to facilitate optimal voicing and reduce responsible for pitch control during poor compensations for weakness, and voicing.29 a combination of both. Such treatments are available at regional and national voice centers where an individual may Vocal Diffi culties from consult with a laryngologist (an ear, nose, Vagus Nerve Damage throat physician specializing in voice), a Voice impairment arises when the speech language pathologist specializing vagus nerve is damaged. The most dev- in voice, a registered nurse, and oc- astating impairment arises when damage casionally a singing teacher who works occurs to the recurrent or superior directly with the medical team. laryngeal nerves.30 Injury to the recur- Superior laryngeal nerve injuries rent laryngeal nerve impairs the ability Individuals with recurrent laryngeal have similarly devastating effects on of the vocal folds to open and close by nerve injuries frequently complain of voicing. Because the superior laryngeal weakening or paralyzing the muscles feeling out of breath during speaking and nerve is responsible for sensation in the responsible for these actions. At best, singing. The cause of nerve injuries arises larynx, damage to this nerve can either poor closure of the vocal folds leaves from complete severing of the nerve, leave an individual with hyposensitivity, a speaker or singer with a soft, breathy, partial tearing of the nerve, stretching placing him or her at risk for aspira- the nerve, compressing the nerve, or tion because saliva and food can enter asthenic voice—unable to sustain sound 38 for more than 4–5 seconds at a time.
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