The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the organ of Corti, the sensory organ of hearing, which is distributed along the partition separating the fluid chambers in the coiled tapered tube of the cochlea.
The basilar membrane is a stiff structural element within the cochlea of the inner ear which separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani. The basilar membrane moves up and down in response to incoming sound waves, which are converted to traveling waves on the basilar membrane.
The organ of Corti, or spiral organ, is the receptor organ for hearing and is located in the mammalian cochlea. This highly varied strip of epithelial cells allows for transduction of auditory signals into nerve impulses' action potential. Transduction occurs through vibrations of structures in the inner ear causing displacement of cochlear fluid and movement of hair cells at the organ of Corti to produce electrochemical signals.
Hair cells are the sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates, and in the lateral line organ of fishes. Through mechanotransduction, hair cells detect movement in their environment.
Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. It is also called Scarpa's fluid, after Antonio Scarpa.
Perilymph is an extracellular fluid located within the inner ear. It is found within the scala tympani and scala vestibuli of the cochlea. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid. The major cation in perilymph is sodium, with the values of sodium and potassium concentration in the perilymph being 138 mM and 6.9 mM, respectively. It is also named Cotunnius' liquid and liquor cotunnii for Domenico Cotugno.
Prestin is a protein that is critical to sensitive hearing in mammals. It is encoded by the SLC26A5 gene.
The superior olivary complex (SOC) or superior olive is a collection of brainstem nuclei that is located in pons, functions in multiple aspects of hearing and is an important component of the ascending and descending auditory pathways of the auditory system. The SOC is intimately related to the trapezoid body: most of the cell groups of the SOC are dorsal to this axon bundle while a number of cell groups are embedded in the trapezoid body. Overall, the SOC displays a significant interspecies variation, being largest in bats and rodents and smaller in primates.
The olivocochlear system is a component of the auditory system involved with the descending control of the cochlea. Its nerve fibres, the olivocochlear bundle (OCB), form part of the vestibulocochlear nerve, and project from the superior olivary complex in the brainstem (pons) to the cochlea.
The cochlear amplifier is a positive feedback mechanism within the cochlea that provides acute sensitivity in the mammalian auditory system. The main component of the cochlear amplifier is the outer hair cell (OHC) which increases the amplitude and frequency selectivity of sound vibrations using electromechanical feedback.
Auditory fatigue is defined as a temporary loss of hearing after exposure to sound. This results in a temporary shift of the auditory threshold known as a temporary threshold shift (TTS). The damage can become permanent if sufficient recovery time is not allowed before continued sound exposure. When the hearing loss is rooted from a traumatic occurrence, it may be classified as noise-induced hearing loss, or NIHL.
Annette Catherine Dolphin is a Professor of Pharmacology in the Department of Neuroscience, Physiology and Pharmacology at University College London (UCL).
Peter Dallos is the John Evans Professor of Neuroscience Emeritus, Professor Emeritus of Audiology, Biomedical Engineering and Otolaryngology at Northwestern University. His research pertained to the neurobiology, biophysics and molecular biology of the cochlea. This work provided the basis for the present understanding of the role of outer hair cells in hearing, that of providing amplification in the cochlea. After his retirement in 2012, he became a professional sculptor.
Maria Fitzgerald is a professor in the Department of Neuroscience at University College London.
Anne Jacqueline Ridley is professor of Cell Biology and Head of School for Cellular and Molecular Medicine at the University of Bristol. She was previously a professor at King's College London.
Andrew John King is a Professor of Neurophysiology and Wellcome Trust Principal Research Fellow in the Department of Physiology, Anatomy and Genetics at the University of Oxford and a Fellow of Merton College, Oxford.
(Robert) Charles Swanton is British physician scientist specialising in oncology and cancer research. Swanton is a senior group leader at London's Francis Crick Institute, Royal Society Napier Professor in Cancer and thoracic medical oncologist at University College London and University College London Hospitals, co-director of the Cancer Research UK (CRUK) Lung Cancer Centre of Excellence, and Chief Clinician of Cancer Research UK.
Hensen's cells are a layer of tall supporting cells around the outer hair cells (OHC) in the organ of Corti in the cochlea. Their appearance are upper part wide with lower part narrow, column like cells. One significant morphologic feature of Hensen's cells is the lipid droplets, which are most noticeable at the third and forth turns of the cochlear, the lipid droplets are thought to have association with the auditory process because they are parallel to the innervation. One significant structure found among the Hensen's cells and the hair cells are the gap junctions, which are made of connexins which serve important functions in distribution and connection between cells; the gap junctions enable long distance electrical communication.
Caetano Maria Pacheco Pais dos Reis e Sousa is a senior group leader at the Francis Crick Institute and a professor of Immunology at Imperial College London.
Anant B. Parekh is professor of Physiology at the University of Oxford and a Fellow of Merton College, Oxford.
