| Brain: Cochlear nuclei | ||
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| Dissection of brain-stem. The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. Dorsal view. ("Cochlear nucleus" is labeled on left, fifth from the bottom. ) | ||
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| Terminal nuclei of the cochlear nerve, with their upper connections. (Schematic. ) The vestibular nerve with its terminal nuclei and their efferent fibers have been suppressed. On the other hand, in order not to obscure the trapezoid body, the efferent fibers of the terminal nuclei on the right side have been resected in a considerable portion of their extent. The trapezoid body, therefore, shows only one-half of its fibers, viz. , those which come from the left. 1. Vestibular nerve, divided at its entrance into the medulla oblongata. The vestibular nerve is one of the two branches of the Vestibulocochlear nerve (the Cochlear nerve being the other The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure 2. Cochlear nerve. The cochlear nerve (also auditory nerve or VIIIth nerve) is part of the Vestibulocochlear nerve, (or 8th Cranial nerve) that is found in higher 3. Accessory nucleus of acoustic nerve. The spinal accessory nucleus lies within the cervical Spinal cord (C1-C5 in the ventral horn The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve Cranial nerves, and is responsible for transmitting sound 4. Tuberculum acusticum. 5. Efferent fibers of accessory nucleus. The spinal accessory nucleus lies within the cervical Spinal cord (C1-C5 in the ventral horn 6. Efferent fibers of tuberculum acusticum, forming the striae medullares, with 6’, their direct bundle going to the superior olivary nucleus of the same side; 6’’, their decussating bundles going to the superior olivary nucleus of the opposite side. Winding around the Inferior peduncle and crossing the Area acustica and the Medial eminence are a number of white strands the striae medullares, which 7. Superior olivary nucleus. 8. Trapezoid body. The trapezoid body is part of the Acoustic pathway. It is a bundle of fibers and cells in the Pontine tegmentum. 9. Trapezoid nucleus. 10. Central acoustic tract (lateral lemniscus). 11. Raphé. A raphe has different uses In science Pronounced "RAY-fee") it is most commonly used when describing Diatoms, Seeds, and Animal 12. Cerebrospinal fasciculus. 13. Fourth ventricle. The fourth ventricle is one of the four connected fluid-filled cavities within the human Brain. 14. Inferior peduncle. The upper part of the posterior district of the Medulla oblongata is occupied by the inferior peduncle, a thick rope-like strand situated between the lower part of the Fourth |
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| Latin | nuclei cochleares | |
| Gray's | subject #187 788 | |
| Part of | Medulla | |
| System | Auditory system | |
| Artery | AICA | |
| NeuroNames | hier-717 | |
| Dorlands/Elsevier | n_11/12580764 | |
The cochlear nuclei consist of:
- (a) the dorsal cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and
- (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This is a list of the subjects in Gray's Anatomy: IX Neurology The auditory system is the Sensory system for the sense of hearing. The anterior inferior cerebellar artery passes backward to be distributed to the anterior part of the under surface of the Cerebellum, anastomosing with the Posterior inferior NeuroNames is a system of nomenclature for the human and/or macaque Brain. Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The dorsal cochlear nucleus (DCN also known as the "tuberculum acousticum" is a cortex-like structure on the dorso-lateral surface of the brainstem The upper part of the posterior district of the Medulla oblongata is occupied by the inferior peduncle, a thick rope-like strand situated between the lower part of the Fourth The ventral cochlear nucleus (or anterior, or accessory) placed between the two divisions of the Cochlear nerve, is on the ventral aspect of the The upper part of the posterior district of the Medulla oblongata is occupied by the inferior peduncle, a thick rope-like strand situated between the lower part of the Fourth
Contents |
Anatomy and function
The CN is the first relay station in the auditory system and is located at the dorso-lateral side of the brainstem, spanning the junction of the pons and medulla. Information is brought via the cochlear nerve, also called Cranial nerve VIII, to the CN. The cochlear nucleus can be divided into ventral and dorsal sections (DCN). In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The ventral part can further be divided into anterior and posterior sections (AVCN and PVCN), which are separated by the incoming auditory nerve fibers. The auditory nerve fibers form a highly organized system of connections according to their peripheral innervation of the cochlea. Axons from the spiral ganglion cells of the lower frequency innervate the ventral portions of the dorsal cochlear nucleus and the ventrolateral portions of the anteroventral cochlear nucleus. In contrast, the axons from the higher frequency organ of corti hair cells project to the dorsal portion of the anteroventral cochlear nucleus and the uppermost dorsal portions of the dorsal cochlear nucleus. The mid frequency projections end up in between the two extremes, in this way the frequency spectrum is preserved.
At the level of the cochlear nuclei, the input from the two ears, for the most part, remains separated. There is evidence, however, that a significant number of neurons in the CN receives input from the contralateral CN. Just as the inner hair cells are arranged according to the best frequency (BF), so is the cochlea nucleus. This so-called tonotopic organization is preserved because only a few inner hair cells synapse on the dendrites of a nerve cell in the spiral ganglion, and the axon from that nerve cell synapes on only a very few dendrites in the cochlear nucleus.
Each cochlear nucleus has two parts, dorsal (DCN) and ventral (VCN). The Cochlear Nucleus receives input from each spiral ganglion, and also receives input from other parts of the brain, such as auditory cortex, pontine nuclei, dorsal column nuclei and the second dorsal root ganglion. The inputs from other areas of the brain play a role in sound localization.
Location and projections from the CN
There are three major projections from the cochlear nuclei. Through the medulla, one projection bifurcates, and projects to the contralateral the superior olivary complex (SOC) via the trapezoid body, whilst the other half shoots to the ipsilateral SOC. The trapezoid body is part of the Acoustic pathway. It is a bundle of fibers and cells in the Pontine tegmentum. This projection is called the ventral acoustic stria (or, more commonly, the trapezoid body). Another projection, called the dorsal acoustic stria (DAS, also known as the stria of von Monakow), rises above the medulla into the pons where it hits the nucleus of the lateral lemniscus along with its kin, the intermediate acoustic stria (IAS, also known as the stria of Held). The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the Brain stem. The lateral lemniscus is a tract of Axons in the Brainstem that carries information about sound from the Cochlear nucleus to various brainstem nuclei and The IAS decussates across the medulla, before joining the ascending fibers in the contralateral lateral lemniscus. The lateral lemniscus contains cells of the nuclei of the lateral lemniscus, and in turn projects to the inferior colliculus. The inferior colliculi ( Latin, lower hills) together with the superior colliculi form the eminences of the Corpora quadrigemina, and also part The inferior colliculus receives direct, monosynaptic projections from the superior olivary complex the contralateral dorsal acoustic stria, some classes of stellate neurons of the VCN, as well as from the different nuclei of the lateral lemniscus. All of these inputs terminate in the inferior colliculus, although there are a few small projections that bypass the inferior colliculus and project to the medial geniculate, or other forebrain structures. The principal projection of the inferior colliculus is to the medial geniculate body in the thalamus. The medial geniculate then projects to the auditory cortex, in the superior temporal gyrus.
Cell types
There are four types of principal cells found in the cochlear nuclei: Bushy cells, stellate cells, octopus cells, and fusiform cells.
- Bushy cells are found in the anterior ventral cochlear nucleus (AVCN). These can be divided into spherical and globular bushy cells, depending on their appearance, and also their location. Within the AVCN here is an area of large spherical cells; caudal to this are smaller spherical cells, and globular cells. They have a few (1-4) very short dendrites with numerous small branching, which cause it to resemble a “bush”. The bushy cells are only found in the ventral portion of the cochlear nucleus. The bushy cells have specialized electrical properties that allow them to transmit timing information from the auditory nerve to more central areas of the auditory system. Some bushy cells can even improve the precision of the timing information. Bushy cells have responses very similar to those in the auditory nerve. The primary difference is that spontaneous activity is decreased by stimulation by adjacent frequencies, therefore leading to an even sharper tuning curve than seen in auditory nerve cells. These cells are usually innervated only by a selected few axons, which dominate its firing patterns. These afferent axons wrap their terminal branches around the entire soma, creating a large synapse onto the bushy cells. Therefore, a single unit recording of an electrically stimulated bushy neuron characteristically produces exactly one action potential and constitutes the primary response.
- Stellate cells, morphologically, have a radial, star-like dendritic tree, which is where they get their name. They are also called, chopper cells, in reference to their ability to fire a regularly-spaced train of action potentials for the duration of a tonal or noise stimulus. The chopping pattern is intrinsic to the electrical excitability of the stellate cell, and the firing rate depends on the strength of the auditory input more than on the frequency.
- Octopus cells are found in a small region of the Posterior Ventral Cochlear Nucleus (PVCN). The distinguishing features of these cells are their long, thick dendrites that typically emanate from one side of the cell body. Octopus cells produce an "Onset Response" to simple tonal stimuli. That is, they respond only at the onset of a specific frequency or frequency range at higher amplitudes. The octopus cells can fire with some of the highest temporal precision of any neuron in the brain. Electrical stimuli to the auditory nerve has been shown to evoke a graded post synaptic potential in the octopus cells. These EPSP’s are very brief. The octopus cells are thought to be important extracting timing information. It has been reported that these cells can respond to click trains at a rate of 800 Hz.
- Fusiform cells (also known as pyramidal cells) are found in the Dorsal Cochlear Nucleus (DCN). See the separate page concerning the DCN. The dorsal cochlear nucleus (DCN also known as the "tuberculum acousticum" is a cortex-like structure on the dorso-lateral surface of the brainstem
Structures
The input of auditory stimulus is through the Auditory Nerve (CN VIII). The auditory stimulus further travels through the AVCN as neural impulses and branches through the following structures:
- Medial superior olive (MSO) via Trapezoid Body (TB) – Ipsilateral and contralateral stimulation for low frequency sounds.
- Lateral superior olive (LSO) directly and via TB – Ipsilateral stimulation for high frequency sounds.
- Medial Nucleus of Trapezoid body (MNTB) – Contralateral stimulation. The trapezoid body is part of the Acoustic pathway. It is a bundle of fibers and cells in the Pontine tegmentum.
- Inferior colliculus – Contralateral stimulation. The inferior colliculi ( Latin, lower hills) together with the superior colliculi form the eminences of the Corpora quadrigemina, and also part
- Neurotransmitters: There are four neurotransmitters responsible for transmission of neural impulses, namely, GABA, Norepinephrine, Glutamate, and Acetylcholine. See Chemical synapse for an introduction to concepts and terminology used in this article Gamma-aminobutyric acid (GABA is the chief inhibitory Neurotransmitter in the Mammalian Central nervous system. Norepinephrine ( INN) (abbreviated norepi or NE) or noradrenaline ( BAN) (abbreviated NA or NAd) is a Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its The Chemical compound acetylcholine (often abbreviated ACh) is a Neurotransmitter in both the Peripheral nervous system (PNS and Central
- Periolivary nuclei (PON) – Ipsilateral and Contralateral stimulation.
- Lateral lemniscus (LL) and Lemniscal Nuclei (LN) – Ipsilateral and Contralateral Stimulation. The lateral lemniscus is a tract of Axons in the Brainstem that carries information about sound from the Cochlear nucleus to various brainstem nuclei and
See also
References
Additional images
 Dissection of brain-stem. The auditory system is the Sensory system for the sense of hearing. The cochlear nerve (also auditory nerve or VIIIth nerve) is part of the Vestibulocochlear nerve, (or 8th Cranial nerve) that is found in higher Lateral view. |
 The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue. |
 Primary terminal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral view. |
 Scheme showing the course of the fibers of the lemniscus; medial lemniscus in blue, lateral in red. |
External links
This article was originally based on an entry from a public domain edition of Gray's Anatomy. The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone Henry Gray's Anatomy of the Human Body (or Gray's Anatomy as it has commonly been shortened is an English-language Human anatomy Textbook As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
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