The cochlear nuclear complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus and the dorsal cochlear nucleus. The ventral cochlear nucleus is unlayered. Auditory nerve fibers, fibers that travel through the auditory nerve carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus. At the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus. All acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins; the outputs from the cochlear nuclei are received in higher regions of the auditory brainstem. The cochlear nuclei are located at the dorso-lateral side of the brainstem, spanning the junction of the pons and medulla; the ventral cochlear nucleus on the ventral aspect of the brain stem, ventrolateral to the inferior peduncle. The dorsal cochlear nucleus known as the tuberculum acusticum or acoustic tubercle, curves over the VCN and wraps around the cerebellar peduncle.
The VCN is further divided by the nerve root into the posteroventral cochlear nucleus and the anteroventral cochlear nucleus. The major input to the cochlear nucleus is from the auditory nerve, a part of cranial nerve VIII; the auditory nerve fibers form a organized system of connections according to their peripheral innervation of the cochlea. Axons from the spiral ganglion cells of the lower frequencies innervate the ventrolateral portions of the ventral cochlear nucleus and lateral-ventral portions of the dorsal cochlear nucleus; the axons from the higher frequency organ of corti hair cells project to the dorsal portion of the ventral cochlear nucleus and the dorsal-medial portions of the dorsal cochlear nucleus. The mid frequency projections end up in between the two extremes; this tonotopic organization is preserved because only a few inner hair cells synapse on the dendrites of a nerve cell in the spiral ganglion, the axon from that nerve cell synapses on only a few dendrites in the cochlear nucleus.
In contrast with the VCN that receives all acoustic input from the auditory nerve, the DCN receives input not only from the auditory nerve but it receives acoustic input from neurons in the VCN. The DCN is therefore in a sense a second order sensory nucleus; the cochlear nuclei have long been thought to receive input only from the ipsilateral ear. There is evidence, for stimulation from the contralateral ear via the contralateral CN, the somatosensory parts of the brain. There are three major fiber bundles, axons of cochlear nuclear neurons, that carry information from the cochlear nuclei to targets that are on the opposite side of the brain. Through the medulla, one projection goes to the contralateral superior olivary complex via the trapezoid body, whilst the other half shoots to the ipsilateral SOC; this pathway is called the ventral acoustic stria. Another pathway, called the dorsal acoustic stria, rises above the medulla into the pons where it hits the nuclei of the lateral lemniscus along with its kin, the intermediate acoustic stria.
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, in turn projects to the inferior colliculus; 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. Most 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. Medial superior olive via trapezoid body – Ipsilateral and contralateral stimulation for low frequency sounds. Lateral superior olive directly and via TB – Ipsilateral stimulation for high frequency sounds. Medial nucleus of trapezoid body – Contralateral stimulation. Inferior colliculus – Contralateral stimulation.
Periolivary nuclei – Ipsilateral and contralateral stimulation. Lateral lemniscus and lemniscal nuclei – Ipsilateral and contralateral stimulation. Three types of principal cells convey information out of the ventral cochlear nucleus: Bushy cells, stellate cells, octopus cells. Bushy cells are found in the anterior ventral cochlear nucleus; these can be further divided into large spherical, small spherical and globular bushy cells, depending on their appearance, their location. Within the AVCN there is an area of large spherical cells. An important difference between these subtypes is that they project to differing targets in the superior olivary complex. Large spherical bushy cells project to the contralateral medial superior olive. Globular bushy cells project to the contralateral medial nucleus of the trapezoid body, small spherical bushy cells project to the lateral superior olive, they have a few short dendrites with numerous small branching, which cause it to resemble a “bush”. The bushy cells have specialized electrical propertie
The salivatory nuclei are the superior salivatory nucleus, the inferior salivatory nucleus that innervate the salivary glands. They are located in the pontine tegmentum in the brainstem, they both belong to the cranial nerve nuclei. The superior salivatory nucleus innervates the submandibular gland and the sublingual gland and is part of the facial nerveThe inferior salivatory nucleus innervates the parotid gland and is one of the components of the glossopharyngeal nerve; the superior salivatory nucleus of the facial nerve is a visceromotor cranial nerve nucleus located in the pontine tegmentum. It is one of the salivatory nuclei. Parasympathetic efferent fibers of the facial nerve arise according to some authors from the small cells of the facial nucleus, or according to others from a special nucleus of cells scattered in the reticular formation, dorso-medial to the facial nucleus – the superior salivatory nucleus; some of the preganglionic fibers travel along the greater petrosal nerve through the pterygoid canal (where they join the postsynaptic fibers of the deep petrosal nerve and are called the nerve of the pterygoid canal and synapse in the pterygopalatine ganglion, whereupon the postganglionic, efferent fibers travel to innervate the lacrimal gland and the mucosal glands of the nose and pharynx.
Preganglionic parasympathetic fibers are distributed via the chorda tympani and lingual nerves to the submandibular ganglion, thence by postganglionic fibers to the submandibular and sublingual salivary glands. The term "lacrimal nucleus" is sometimes used to refer to a portion of the superior salivatory nucleus; the inferior salivatory nucleus is a cluster of neurons in the pontine tegmentum, just above its junction with the medulla. It is the general visceral efferent component of the glossopharyngeal nerve supplying the parasympathetic input to the parotid gland for salivation, it lies caudal to the superior salivatory nucleus and just above the upper end of the dorsal nucleus of the vagus nerve in the medulla. The preganglionic parasympathetic fibres originate in the inferior salivatory nucleus of the glossopharyngeal nerve, they leave the glossopharngeal nerve by its tympanic branch and pass via the tympanic plexus and the lesser petrosal nerve to the otic ganglion. Here, the fibres synapse, the postganglionic fibers pass by communicating branches to the auriculotemporal nerve, which conveys them to the parotid gland.
They produce secretomotor effects. Parasympathetic input from fibers of the inferior salivatory nucleus stimulates the parotid gland to produce vasodilation and secrete saliva; this article incorporates text in the public domain from the 20th edition of Gray's Anatomy Kiernan, John A.. Barr's The Human Nervous System: An Anatomical Viewpoint. Lippincott Williams & Wilkins. P. 150. ISBN 0-7817-5154-3. Diagram Diagram Cluster Headache Pathogenesis https://web.archive.org/web/20060907231522/http://sprojects.mmi.mcgill.ca/cns/histo/systems/cranialnerves/main.htm
The basilar sulcus is a groove in the pons, part of the brainstem. The basilar sulcus lies in the midline of the pons on its anterior surface; the basilar artery runs within the basilar sulcus. The basilar sulcus is bounded on either side by an eminence caused by the descent of the cerebrospinal fibers through the substance of the pons; this article incorporates text in the public domain from page 785 of the 20th edition of Gray's Anatomy https://web.archive.org/web/20100426123803/http://anatomy.med.umich.edu/atlas/n2a4p1.html
Costanzo Varolio, Latinized as Constantius Varolius, was an Italian anatomist and a papal physician to Gregory XIII. Varolio was born in Bologna, he was a pupil of the anatomist Giulio Cesare Aranzio, himself a pupil of Vesalius. He received his doctorate in medicine in 1567. In 1569 the Senate of the University of Bologna created an extraordinary chair in surgery for him with responsibility to teach anatomy as well and where a statue of him is housed at the Anatomical Theatre of the Archiginnasio, he is believed to have taught at the Sapienza University of Rome although he is not listed on the roll there. He is known to have had considerable success in Rome both as a physician and as a surgeon and his memorial plaque in that city refers to his great skill in removing stones, he died in Rome. He is best remembered for his work on the cranial nerves, he was the first to examine the brain from its base upwards, in contrast with previous dissections, performed from the top downwards. In 1573 he published this new method of dissecting the brain whereby he separated the brain from the skull and began the dissection from the base.
Varolio described many of the brain's structures for the first time including the pons or pons Varolii, a reflex center of respiration and a communication bridge between spinal cord and brain, the crura cerebri and the ileocecal valve. Another area of interest to him was the mechanism of erectile function. Although the “Musculi erectores penis” had been described by Galen in the 2nd century A. D. this knowledge was lost by the time of Varolio, who re-discovered them and gave a accurate description of the mechanism of erection although his inaccurate attribution of erection to "erector muscles" continued to be believed by most anatomists for three centuries. Varolius' work is the following:De Nervis Opticis nonnullisque aliis praeter communem opinionem in Humano capite observatis. Ad Hieronymum Mercurialem, Patavii apud Paul et Anton. Meiettos fratres, 1573, 8º, 8 and 32 leaves, it consists of a letter to Merculiaris, dated April 1, 1572, his answer, Varolius' reply to the latter. Appended are three woodcuts pertaining to the brain and drawn by Varolius himself.
The engraving is distinct and instructive. A second work by Varolius, a teleologic physiology of man, was published for the first time after his death: Anatomiae sive de resolutione corporis humani ad Caesarem Mediovillanum libri iv, Eiusdem Varolii et Hieron. Mercrialis De nervis Opticis, etc. epistolae, apud Joh. Wechelum et Petr. Fischerum consortes, 1591, 8º, 8 and 184 pp; this contains one illustration. The former book is republished as a part of this work with unchanged text and the woodcuts recarved in a somewhat different manner. Il Catalogo Unico delle Biblioteche Italiane Bio Infobank Library Tubbs RS, Loukas M, Shoja MM, et al.. "Costanzo Varolio and the Pons Varolli". Neurosurgery. 62: 734–7, discussion 734–7. Doi:10.1227/01.neu.0000317323.63859.2a. PMID 18425020. Gaetano Luigi Marini, Degli archiatri pontifici, 2 vols. Milestones in Neuroscience Research, Eric H. Chudler. Varolio at the Galileo Project Richard S. Westfall, Department of History and Philosophy of Science, Indiana University
Basal plate (neural tube)
In the developing nervous system, the basal plate is the region of the neural tube ventral to the sulcus limitans. It extends from the rostral mesencephalon to the end of the spinal cord and contains motor neurons, whereas neurons found in the alar plate are associated with sensory functions; the cell types of the basal plate include four types of interneuron. The left and right sides of the basal plate are continuous, but during neurulation they become separated by the floor plate, this process is directed by the notochord. Differentiation of neurons in the basal plate is under the influence of the protein Sonic hedgehog released by ventralizing structures, such as the notochord and floor plate. BibliographyJohn A. Kiernan. Barr's the Human Nervous System: An Anatomical Viewpoint. Hagerstown, MD: Lippincott Williams & Wilkins. ISBN 0-7817-5154-3. Overview at temple.edu ancil-451 at NeuroNames
The cerebellum is a major feature of the hindbrain of all vertebrates. Although smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or larger. In humans, the cerebellum plays an important role in motor control, it may be involved in some cognitive functions such as attention and language as well as in regulating fear and pleasure responses, but its movement-related functions are the most solidly established. The human cerebellum does not initiate movement, but contributes to coordination and accurate timing: it receives input from sensory systems of the spinal cord and from other parts of the brain, integrates these inputs to fine-tune motor activity. Cerebellar damage produces disorders in fine movement, equilibrium and motor learning in humans. Anatomically, the human cerebellum has the appearance of a separate structure attached to the bottom of the brain, tucked underneath the cerebral hemispheres, its cortical surface is covered with finely spaced parallel grooves, in striking contrast to the broad irregular convolutions of the cerebral cortex.
These parallel grooves conceal the fact that the cerebellar cortex is a continuous thin layer of tissue folded in the style of an accordion. Within this thin layer are several types of neurons with a regular arrangement, the most important being Purkinje cells and granule cells; this complex neural organization gives rise to a massive signal-processing capability, but all of the output from the cerebellar cortex passes through a set of small deep nuclei lying in the white matter interior of the cerebellum. In addition to its direct role in motor control, the cerebellum is necessary for several types of motor learning, most notably learning to adjust to changes in sensorimotor relationships. Several theoretical models have been developed to explain sensorimotor calibration in terms of synaptic plasticity within the cerebellum; these models derive from those formulated by David Marr and James Albus, based on the observation that each cerebellar Purkinje cell receives two different types of input: one comprises thousands of weak inputs from the parallel fibers of the granule cells.
The basic concept of the Marr–Albus theory is that the climbing fiber serves as a "teaching signal", which induces a long-lasting change in the strength of parallel fiber inputs. Observations of long-term depression in parallel fiber inputs have provided support for theories of this type, but their validity remains controversial. At the level of gross anatomy, the cerebellum consists of a folded layer of cortex, with white matter underneath and a fluid-filled ventricle at the base. Four deep cerebellar nuclei are embedded in the white matter; each part of the cortex consists of the same small set of neuronal elements, laid out in a stereotyped geometry. At an intermediate level, the cerebellum and its auxiliary structures can be separated into several hundred or thousand independently functioning modules called "microzones" or "microcompartments"; the cerebellum is located in the posterior cranial fossa. The fourth ventricle and medulla are in front of the cerebellum, it is separated from the overlying cerebrum by a layer of leathery dura mater, the tentorium cerebelli.
Anatomists classify the cerebellum as part of the metencephalon, which includes the pons. Like the cerebral cortex, the cerebellum is divided into two hemispheres. A set of large folds is, by convention, used to divide the overall structure into 10 smaller "lobules"; because of its large number of tiny granule cells, the cerebellum contains more neurons than the total from the rest of the brain, but takes up only 10% of the total brain volume. The number of neurons in the cerebellum is related to the number of neurons in the neocortex. There are about 3.6 times as many neurons in the cerebellum as in the neocortex, a ratio, conserved across many different mammalian species. The unusual surface appearance of the cerebellum conceals the fact that most of its volume is made up of a tightly folded layer of gray matter: the cerebellar cortex; each ridge or gyrus in this layer is called a folium. It is estimated that, if the human cerebellar cortex were unfolded, it would give rise to a layer of neural tissue about 1 meter long and averaging 5 centimeters wide—a total surface area of about 500 square cm, packed within a volume of dimensions 6 cm × 5 cm × 10 cm.
Underneath the gray matter of the cortex lies white matter, made up of myelinated nerve fibers running to and from the cortex. Embedded within the white matter—which is sometimes called the arbor vitae because of its branched, tree-like appearance in cross-section—are four deep cerebellar nuclei, composed of gray matter. Connecting the cerebellum to different parts of the nervous system are three paired cerebellar peduncles; these are the superior cerebellar peduncle, the middle cerebellar peduncle and the inferior cerebellar peduncle, named by their position relative to the vermis. The superior cerebellar peduncle is an output to the cerebral cortex, carrying efferent fibers via thalamic nuclei to upper motor neurons in the cerebral cortex; the fibers arise from the deep cerebellar nuclei. The middle cerebellar peduncle is connected to the pons and receives all of its input from the pons from the pontine nuclei; the input to the pons is from the cerebral cortex and is relayed from the pontine nuclei via transverse pontine fibers to the cerebellum
The pontine arteries are a number of small vessels which come off at right angles from either side of the basilar artery and supply the pons and adjacent parts of the brain. Superior cerebellar artery