Spiral ganglion: Difference between revisions

Spiral ganglion
Spiral ganglion
	Transverse section of the cochlear duct of a fetal cat. (Ganglion spirale is labeled at top, second from left.)
	Part of the cochlear division of the acoustic nerve, highly magnified.
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Identifiers
Latin	ganglion spirale
MeSH	D013136
TA98	A15.3.03.125
TA2	6319
TH	H3.11.09.3.04068
FMA	53445
	Anatomical terminology [edit on Wikidata]

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The spiral (cochlear) ganglion is a group of neuron cell bodies in the modiolus, the conical central axis of the cochlea. These bipolar neurons innervate the hair cells of the organ of Corti. They project their axons to the ventral and dorsal cochlear nuclei as the cochlear nerve, a branch of the vestibulocochlear nerve (CN VIII).

Structure

Neurons whose cell bodies lie in the spiral ganglion are strung along the bony core of the cochlea, and send fibers (axons) into the central nervous system (CNS). These bipolar neurons are the first neurons in the auditory system to fire an action potential, and supply all of the brain's auditory input. Their dendrites make synaptic contact with the base of hair cells, and their axons are bundled together to form the auditory portion of eighth cranial nerve. The number of neurons in the spiral ganglion is estimated to be about 35,000–50,000.^[1]

Two apparent subtypes of spiral ganglion cells exist. Type I spiral ganglion cells comprise the vast majority of spiral ganglion cells (90–95% in cats and 88% in humans^[2]), and exclusively innervate the inner hair cells. They are myelinated, bipolar neurons. Type II spiral ganglion cells make up the remainder. In contrast to Type I cells, they are unipolar and unmyelinated in most mammals. They innervate the outer hair cells, with each Type II neuron sampling many (15–20) outer hair cells.^[3] In addition, outer hair cells form reciprocal synapses onto Type II spiral ganglion cells, suggesting that the Type II cells have both afferent and efferent roles.^[4]

Development

The rudiment of the cochlear nerve appears about the end of the third week as a group of ganglion cells closely applied to the cephalic edge of the auditory vesicle. The ganglion gradually splits into two parts, the vestibular ganglion and the spiral ganglion. The axons of neurons in the spiral ganglion travel to the brainstem, forming the cochlear nerve.

Gallery

Diagrammatic longitudinal section of the cochlea
Organ of Corti

References

This article incorporates text in the public domain from page 1051 of the 20th edition of Gray's Anatomy (1918)

^ Mark F. Bear; Barry W. Connors & Michael A. Paradiso (2006). Neuroscience. Lippincott Williams & Wilkins. ISBN 0-7817-6003-8.
^ Douglas B. Webster; Arthur N. Popper; Richard R. Fay, eds. (1992). The Mammalian Auditory Pathway: Neuroanatomy. Springer-Verlag. ISBN 0-387-97800-3.
^ H Spoendlin (1972). "Innervation densities of the cochlea". Acta Otolaryngol. 73 (2): 235–48. doi:10.3109/00016487209138937. PMID 5015157.
^ JB Nadol Jr (1990). "Synaptic morphology of inner and outer hair cells of the human organ of Corti". J Elect Micr Tech.

External links

Slide and overview at anatomy.dal.ca
Slide at cytochemistry.net
Image Archived 2016-03-03 at the Wayback Machine at University of New England, Maine

[1] Mark F. Bear; Barry W. Connors & Michael A. Paradiso (2006). Neuroscience. Lippincott Williams & Wilkins. ISBN 0-7817-6003-8.

[2] Douglas B. Webster; Arthur N. Popper; Richard R. Fay, eds. (1992). The Mammalian Auditory Pathway: Neuroanatomy. Springer-Verlag. ISBN 0-387-97800-3.

[3] H Spoendlin (1972). "Innervation densities of the cochlea". Acta Otolaryngol. 73 (2): 235–48. doi:10.3109/00016487209138937. PMID 5015157.

[4] JB Nadol Jr (1990). "Synaptic morphology of inner and outer hair cells of the human organ of Corti". J Elect Micr Tech.

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@@ Line 1: / Line 1: @@
+{{Short description|Anatomical structure}}
 {{Infobox anatomy
 | Name        = Spiral ganglion
@@ Line 9: / Line 10: @@
 | Precursor   =
 }}
-The '''spiral (cochlear) ganglion''' is a group of neuron cell bodies in the [[Modiolus (cochlea)|modiolus]], the conical shaped central axis of the [[cochlea]]. These [[Bipolar neuron|bipolar neurons]] innervate the [[Hair cell|hair cells]] of the [[organ of Corti]]. They neurons send their axons to the cochlear nuclei in the brainstem as the [[cochlear nerve]] a branch of the [[vestibulocochlear nerve]] (CN VIII).
+The '''spiral (cochlear) ganglion''' is a group of neuron cell bodies in the [[Modiolus (cochlea)|modiolus]], the conical central axis of the [[cochlea]]. These [[bipolar neuron]]s innervate the [[hair cell]]s of the [[organ of Corti]]. They project their axons to the [[Ventral cochlear nucleus|ventral]] and [[Dorsal cochlear nucleus|dorsal cochlear nuclei]] as the [[cochlear nerve]], a branch of the [[vestibulocochlear nerve]] (CN VIII).
 ==Structure==
-[[Neurons]] whose [[cell body|cell bodies]] lie in the spiral ganglion are strung along the bony core of the cochlea, and send fibers ([[axon]]s) into the [[central nervous system]] (CNS). These [[Bipolar neuron|bipolar]] neurons are the first neurons in the [[auditory system]] to fire an action potential, and supply all of the brain's auditory input. Their [[dendrites]] make [[Synapse|synaptic]] contact with the base of [[hair cell]]s, and their axons are bundled together to form the auditory portion of [[eighth cranial nerve]].  The number of neurons in the spiral ganglion is estimated to be about 35,000–50,000.<ref>{{Cite book| title = Neuroscience |author1=Mark F. Bear |author2=Barry W. Connors |author3=Michael A. Paradiso  |last-author-amp=yes | publisher = Lippincott Williams & Wilkins | year = 2006 | isbn = 0-7817-6003-8 | url = https://books.google.com/books?id=DbahEn-y6AoC&pg=PA359&dq=%22spiral+ganglion%22+35000 }}</ref>
+[[Neurons]] whose [[cell body|cell bodies]] lie in the spiral ganglion are strung along the bony core of the cochlea, and send fibers ([[axon]]s) into the [[central nervous system]] (CNS). These [[bipolar neuron]]s are the first neurons in the [[auditory system]] to fire an action potential, and supply all of the brain's auditory input. Their [[dendrites]] make [[Synapse|synaptic]] contact with the base of [[hair cell]]s, and their axons are bundled together to form the auditory portion of [[eighth cranial nerve]].  The number of neurons in the spiral ganglion is estimated to be about 35,000–50,000.<ref>{{Cite book| title = Neuroscience |author1=Mark F. Bear |author2=Barry W. Connors |author3=Michael A. Paradiso  |name-list-style=amp | publisher = Lippincott Williams & Wilkins | year = 2006 | isbn = 0-7817-6003-8 | url = https://books.google.com/books?id=DbahEn-y6AoC&q=%22spiral+ganglion%22+35000&pg=PA359 }}</ref>
-Two apparent subtypes of spiral ganglion cells exist.  Type I spiral ganglion cells comprise the vast majority of spiral ganglion cells (90-95% in cats and 88% in humans<ref>{{Cite book| title = The Mammalian Auditory Pathway: Neuroanatomy |editor1=Douglas B. Webster |editor2=Arthur N. Popper |editor3=Richard R. Fay | publisher = Springer-Verlag | year = 1992 | isbn = 0-387-97800-3 | url = https://www.amazon.com/Mammalian-Auditory-Pathway-Neuroanatomy-Springer/dp/0387978003 }}</ref>), and exclusively innervate the [[inner hair cells]].  They are myelinated, bipolar neurons.  Type II spiral ganglion cells make up the remainder.  In contrast to Type I cells, they are unipolar and unmyelinated in most mammals.  They innervate the [[outer hair cells]], with each Type II neuron sampling many (15-20) outer hair cells.<ref>{{Cite journal| title =Innervation densities of the cochlea | author = H Spoendlin | year = 1972 | journal = Acta Otolaryngol }}</ref>  In addition, outer hair cells form reciprocal synapses onto Type II spiral ganglion cells, suggesting that the Type II cells have both afferent and efferent roles.<ref>{{Cite journal| title = Synaptic morphology of inner and outer hair cells of the human organ of Corti | author = JB Nadol Jr | year = 1990 | journal = J Elect Micr Tech }}</ref>
+Two apparent subtypes of spiral ganglion cells exist.  Type I spiral ganglion cells comprise the vast majority of spiral ganglion cells (90–95% in cats and 88% in humans<ref>{{Cite book| title = The Mammalian Auditory Pathway: Neuroanatomy |editor1=Douglas B. Webster |editor2=Arthur N. Popper |editor3=Richard R. Fay | publisher = Springer-Verlag | year = 1992 | isbn = 0-387-97800-3 }}</ref>), and exclusively innervate the [[inner hair cells]].  They are myelinated, bipolar neurons.  Type II spiral ganglion cells make up the remainder.  In contrast to Type I cells, they are unipolar and unmyelinated in most mammals.  They innervate the [[outer hair cells]], with each Type II neuron sampling many (15–20) outer hair cells.<ref>{{Cite journal| title =Innervation densities of the cochlea | author = H Spoendlin | year = 1972 | journal = Acta Otolaryngol | volume = 73 | issue = 2 | pages = 235–48 | doi = 10.3109/00016487209138937 | pmid = 5015157 }}</ref>  In addition, outer hair cells form reciprocal synapses onto Type II spiral ganglion cells, suggesting that the Type II cells have both afferent and efferent roles.<ref>{{Cite journal| title = Synaptic morphology of inner and outer hair cells of the human organ of Corti | author = JB Nadol Jr | year = 1990 | journal = J Elect Micr Tech }}</ref>
 ===Development===
-The [[rudiment (biology)|rudiment]] of the [[cochlear nerve]] appears about the end of the third week as a group of [[ganglion]] cells closely applied to the cephalic edge of the [[auditory vesicle]]. The ganglion gradually splits into two parts, the [[vestibular ganglion]] and the spiral ganglion. The axons of neurons in the spiral ganglion travel to the [[brainstem]] forming the [[cochlear nerve]].
+The [[rudiment (biology)|rudiment]] of the [[cochlear nerve]] appears about the end of the third week as a group of [[ganglion]] cells closely applied to the cephalic edge of the [[auditory vesicle]]. The ganglion gradually splits into two parts, the [[vestibular ganglion]] and the spiral ganglion. The axons of neurons in the spiral ganglion travel to the [[brainstem]], forming the [[cochlear nerve]].
 ==Gallery==
 <gallery>
 file:Gray928.png|Diagrammatic longitudinal section of the cochlea
-file:Organ of corti.svg|[[Organ of corti]]
+file:Organ of corti.svg|[[Organ of Corti]]
 </gallery>
@@ Line 32: / Line 33: @@
 * [http://www.anatomy.dal.ca/Human_Histology/Lab4/96LL.html Slide and overview at anatomy.dal.ca]
 * [http://www.cytochemistry.net/microanatomy/Ear/spiral_ganglion4.jpg Slide at cytochemistry.net]
-* [http://faculty.une.edu/com/abell/histo/cochleaw.jpg Image] at [[University of New England, Maine]]
+* [http://faculty.une.edu/com/abell/histo/cochleaw.jpg Image] {{Webarchive|url=https://web.archive.org/web/20160303181431/http://faculty.une.edu/com/abell/histo/cochleaw.jpg |date=2016-03-03 }} at [[University of New England, Maine]]
 {{Auditory and vestibular pathways}}
@@ Line 41: / Line 42: @@
 [[Category:Sensory ganglia]]
 [[Category:Vestibulocochlear nerve]]
+[[Category:Otology]]
+[[Category:Audiology]]