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Auditory Neuropathy Spectrum Disorder and Retrocochlear Disorders in Adults and Children
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
In the physiology of audition, sound energy is transduced to electrical stimuli in the cochlea and transmitted via the auditory nerve. The inner hair cells in the organ of Corti (see Figure 69.1) are responsible for this transduction process as has been shown by Russell and Sellick56 who first demonstrated the importance of the inner hair cells in this process. The afferent auditory nerve consists of 95% type I myelinated nerve fibres (with many type I nerve fibres innervating one inner hair cell), and 5% type II nerve fibres (each type II nerve fibre innervating many outer hair cells (OHCs)). The cell bodies of both these types of bipolar neurons lie in the spiral ganglion. The arrangement of type I neurons in relation to inner hair cells is conducive to synchronous neural impulses whereas the arrangement of type II neurons is not.57 Thus these respective neural anatomical arrangements have implications in relation to the diagnosis of AN, where it is proposed that the afferent neural pathway is involved (Figure 69.1).
Gangliocytoma and Lhermitte–Duclos Disease
Published in Dongyou Liu, Tumors and Cancers, 2017
Neuron is the basic cell of the nervous system that contains a nucleus within a cell body (perikaryon) and extends one or more processes (usually an axon and one or more dendrites). A neuron with an axon only is classified as unipolar neuron, that with an axon and a dendrite is classified as bipolar neuron, and that with an axon and two or more dendrites is classified as multipolar neuron, which is the most common type and widely distributed in the CNS. The axon conducts the impulses to the dendrite of another neuron or to an effector organ. The dendrites receive stimuli from a receptor organ or other nerves and transmit through the neuron to the axon. According to the direction in which they conduct impulses, neurons are categorized into three groups: (i) afferent or sensory neurons (which conduct impulses from a receptor to a center), (ii) efferent or motor neurons (which carry impulses away from a center to an organ of response), and (iii) interneurons (which conduct impulses from afferent to efferent neurons). The point at which an impulse is transmitted from one neuron to another is known as synapse.
Frailty, Nutrition, and the Elderly
Published in David Heber, Zhaoping Li, Primary Care Nutrition, 2017
The sense of smell is mediated through stimulation of the olfactory receptor cells by volatile chemicals. To stimulate the olfactory receptors, airborne molecules must pass through the nasal cavity with relatively turbulent air currents and contact the receptors. Odorants can also be perceived by entering the nose posteriorly through the nasopharynx to reach the olfactory receptor via retronasal olfaction. Each olfactory receptor cell is a primary sensory bipolar neuron. The average nasal cavity contains more than 100 million such neurons. There are more than 900 genes encoding these receptors. The olfactory neurons are unique because they are generated throughout life by the underlying basal cells. New receptor cells are generated approximately every 30–60 days.
Nose to brain transport pathways an overview: potential of nanostructured lipid carriers in nose to brain targeting
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Kousalya Selvaraj, Kuppusamy Gowthamarajan, Veera Venkata Satyanarayana Reddy Karri
The nose is a complex structure. The nasal cavity is divided into three regions namely vestibule, respiratory and olfactory region. Vestibule region is not involved in the absorption functions and it is the anterior external region opening to the nasal cavity. The respiratory epithelium consists of ciliated and non-ciliated columnar cells, mucus secreting goblet cells and basal cells. The respiratory region is mainly involved in the drug absorption and the surface area of respiratory region is approximately 160 cm2 in humans. The third region is olfactory region consists of olfactory receptor cells, basal and sustentacular cells. The olfactory region has a surface area of 10 cm2. Olfactory receptor neurons are bipolar neurons involves in the transduction of information from epithelium to olfactory bulb [13]. The olfactory pathway is explained in the following section.
Estimation of the status of spiral ganglion neurons and Schwann cells in the auditory neural degeneration mouse using the auditory brainstem response
Published in Acta Oto-Laryngologica, 2018
Zhi-Jian Zhang, Hong-Xia Guan, Kun Yang, Bo-Kui Xiao, Hua Liao, Yang Jiang, Tao Zhou, Qing-Quan Hua
Sensorineural hearing loss (SNHL), which results from pathologies of the cochlea and the auditory nerve, is a common communication disorder. Loss of inner ear hair cells and degeneration of spiral ganglion neurons (SGNs) in the cochlea are the typical causes for SNHL. Currently, gene therapy or stem cell replacement therapy is not yet available, cochlear implantation is the best hearing rehabilitation strategy for severe-to-profound SNHL and auditory neuropathy (AN) patients. Cochlear implants (CIs) bypass the lost hair cells and directly stimulate SGNs, of which the axons form the auditory nerve. Proper functioning of CIs hence mainly depends on the existence of sufficient and functional auditory neuronal structures especially the SGNs in the deafened ears, and the status of these remnant neural structures likely directly impacts cochlear implant outcomes [1–3]. SGNs are bipolar neurons that are enwrapped by Schwann cells in the cochlea Rosenthal’s canal. Schwann cells play important roles in providing myelin layers, as well as in energy conservation, neurotrophin support, and in promoting SGNs health and survival [4–7], contribute to an important part as the status of the auditory neuronal structures, therefore, are worthy of detailed investigation.
Impact of intranasal application of nerve growth factor on the olfactory epithelium in rats with chemically induced diabetes
Published in Ultrastructural Pathology, 2018
Sidika Yalim, Kenan Dağlıoğlu, Gülfidan Coskun, Sait Polat
Light microscopic examination of the OE reveals normal pseudostratified columnar epithelium with olfactory sensory neurons (OSNs), sustentacular (supporting) cells, basal cells, and ciliated cells in the control group (Figure 1). The olfactory cells are bipolar neurons with modified, nonmotile cilia present at knob-like endings. Receptors for odorants are present on the surface of these cilia. Unlike most neurons, the olfactory cells also turn over constantly. Under the epithelium, lamina propria includes Bowman’s glands, olfactory nerve fibers, and blood vessels. Bowman’s (serous) glands in the submucosa secrete a fluid that washes over the surface epithelium. Lamina propria continues with hyaline cartilage in the deep of the olfactory mucosa.