DOCSLIB.ORG

Control of Hearing Sensitivity by Tectorial Membrane Calcium

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Control of Hearing Sensitivity by Tectorial Membrane Calcium Control of hearing sensitivity by tectorial membrane calcium Clark Elliott Strimbua,1,2, Sonal Prasada,1, Pierre Hakizimanaa, and Anders Fridbergera,3 aDepartment of Clinical and Experimental Medicine, Division of Neurobiology, Linköping University, SE-581 83 Linköping, Sweden Edited by Christine Petit, Institut Pasteur, College de France, INSERM, Université Pierre-et-Marie-Curie, Paris 15, France, and approved February 7, 2019 (received for review March 26, 2018) When sound stimulates the stereocilia on the sensory cells in the tation processes provide the hair cell with a high-pass filter and hearing organ, Ca2+ ions flow through mechanically gated ion the dynamic range of the transduction apparatus is extended. + channels. This Ca2 influx is thought to be important for ensuring Additionally, in both processes, as the MET channels close, they that the mechanically gated channels operate within their most exert a pulling force on the tip links that leads to a measurable sensitive response region, setting the fraction of channels open change in the position of the entire bundle of stereocilia (15, 16). at rest, and possibly for the continued maintenance of stereocilia. This mechanical correlate of adaptation results in active hair + Since the extracellular Ca2 concentration will affect the amount bundle motility that may contribute to the amplification of faint + of Ca2 entering during stimulation, it is important to determine sounds, a function that is critical for hearing (17). Much of the the level of the ion close to the sensory cells. Using fluorescence understanding of the two adaptation processes came from experi- imaging and fluorescence correlation spectroscopy, we measured ments performed on low-frequency hair cells from nonmammalian 2+ the Ca concentration near guinea pig stereocilia in situ. Surpris- vertebrates. Despite the success of the model in explaining the ingly, we found that an acellular accessory structure close to the observed MET currents in these low-frequency cells, recent work 2+ + stereocilia, the tectorial membrane, had much higher Ca than has questioned the extent to which this model of Ca2 -dependent 2+ the surrounding fluid. Loud sounds depleted Ca from the tecto- adaptation applies to mammalian hearing organs. Indeed, one re- 2+ rial membrane, and Ca manipulations had large effects on hair cent report suggests that cochlear hair cell adaptation is, in fact, + cell function. Hence, the tectorial membrane contributes to control independent of Ca2 entry (18), while others reached the opposite of hearing sensitivity by influencing the ionic environment around conclusion (19). NEUROSCIENCE the stereocilia. Due to its obvious physiological importance, significant effort + was expended in measuring the level of Ca2 in the fluid that hearing | temporary threshold shift | mechanoelectrical transduction | surrounds stereocilia, the endolymph. These measurements, tectorial membrane | calcium which were performed with ion-selective electrodes or by ana- lyzing aspirated endolymph samples, showed values ranging from he sense of hearing depends on mechanically sensitive ion 15 to 40 μM (20–23). With the understanding that the results are Tchannels located near the tips of the stereocilia on the sen- controversial, cochlear hair cells from mice (19) and rats (18) sory hair cells of the inner ear (1). When an acoustic stimulus tend to show little adaptation, and the number of MET channels causes these mechanoelectric transduction (MET) channels to open at rest increases substantially when stereocilia are exposed + be activated, the flow of potassium and calcium ions into the cell to solutions with micromolar [Ca2 ]. + increases (2). Recent data suggest that the Ca2 component of the receptor 2+ 2+ The Ca concentration ([Ca ]) in the vicinity of the MET current may also be important for maintaining the structural channels is functionally important. For instance, it controls the fraction of MET channels that are open at rest [i.e., high calcium Significance near stereocilia tends to close MET channels, whereas lower calcium does the opposite (3)]. Changes in the resting open A new mechanism that contributes to control of hearing sensi- probability alter the amplitude of the “silent current” (4, 5) that tivity is described here. We show that an accessory structure in continuously flows into the sensory cells, causing them to operate − the hearing organ, the tectorial membrane, affects the function at a relatively depolarized membrane potential near 40 mV (6). of inner ear sensory cells by storing calcium ions. When the The continuous depolarization is important in one class of sen- calcium store is depleted, by brief exposure to rock concert-level sory cell, the outer hair cell, where it is thought to facilitate the sounds or by the introduction of calcium chelators, the sound- detection of soft sounds by allowing amplification mediated by evoked responses of the sensory cells decrease. Upon restora- somatic electromotility (7) to operate at auditory frequencies (6). tion of tectorial membrane calcium, sensory cell function returns. Like other sensory receptors, hair cells possess an adaptation This previously unknown mechanism contributes to explaining mechanism that reduces the transduction current in response to the temporary numbness in the ear that follows from listening sustained stimuli (8). The conventional model states that this to sounds that are too loud, a phenomenon that most people adaptation is due to two distinct processes, termed fast and slow experience at some point in their lives. adaptation, which operate on different time scales (9), but which 2+ 2+ both may depend on Ca entry. In fast adaptation, or Ca - Author contributions: C.E.S. and A.F. designed research; C.E.S., S.P., and P.H. performed + mediated channel reclosure, Ca2 ions appear to interact di- research; A.F. analyzed data; and A.F. wrote the paper. rectly with the MET channel or its accessory proteins, causing The authors declare no conflict of interest the channel to rapidly close. Slow adaptation is believed to rely This article is a PNAS Direct Submission. 2+ on the Ca -dependent activation of unconventional myosins This open access article is distributed under Creative Commons Attribution-NonCommercial- (10, 11), which move the upper insertion point of the tip links NoDerivatives License 4.0 (CC BY-NC-ND). (12, 13), the tiny extracellular filaments that control the gating of 1C.E.S. and S.P. contributed equally to this work. the MET channels (14). By adjusting the tension in the tip links, 2Present address: Department of Otolaryngology, Columbia University Medical Center, slow adaptation reduces the MET current following prolonged New York, NY 10032. deflections in the positive direction, thus ensuring that the MET 3To whom correspondence should be addressed. Email: [email protected]. channels maintain their responsiveness. Together, the two adap- www.pnas.org/cgi/doi/10.1073/pnas.1805223116 PNAS Latest Articles | 1of9 Downloaded by guest on September 28, 2021 integrity of stereocilia. When isolated rat or mouse hair cells Results + were exposed to MET channel blockers, the length of individual To measure [Ca2 ] near the hearing organ, we used temporal stereocilia and the architecture of the bundle were altered (24). bone preparations isolated from guinea pigs (26). The prepara- These changes, which were reversible upon washout of the tions retained the middle ear, allowing sound stimulation through 2+ blocker, could also be induced by increasing the internal Ca a loudspeaker positioned in the ear canal, and to ensure cellular 2+ buffering capacity of the hair cells or by decreasing external Ca viability, the preparations were continuously perfused with oxy- to levels around 100 μM. genated tissue culture medium. A small opening at the apex of the 2+ It seems clear that it is important to determine the [Ca ] cochlea allowed a glass microelectrode with 10-μm tip diameter to close to the hair bundles, particularly since a previous study (25) be positioned close to the hearing organ. The electrode was used 2+ suggested that local Ca may be elevated as a result of high to introduce the low-affinity fluorescent indicator Asante Calcium activity of plasma-membrane calcium-ATPase type 2, coupled Red. When excited at 488 nm, this dye emitted red light with + with diffusion barriers imposed by the proximity to the tectorial intensity that depended on the Ca2 level, as well as green light + membrane, an acellular accessory structure close to stereocilia. with very weak Ca2 dependence (27). By taking the ratio between 2+ However, all reported measurements of [Ca ] in the inner ear red and green fluorescence intensities, spatial and temporal vari- 2+ fluids used techniques that lack spatial resolution, so the Ca ations in dye concentration were cancelled out and a sensitive + level near the stereocilia is not known. measure of extracellular [Ca2 ] was obtained. Here, we used fluorescence imaging and spectroscopic mea- + + surements to determine Ca2 in situ. Surprisingly, these experi- High Ca2 Within the Tectorial Membrane. A pivotal finding from + ments revealed that the tectorial membrane had a much higher these experiments was that Ca2 levels were much higher in the + Ca2 concentration than the surrounding endolymph, and that tectorial membrane than in the surrounding fluid. This pattern + reductions in tectorial membrane Ca2 contributed to the acute was evident in single images (Fig. 1A), where high ratios were decrease
Load more

Recommended publications
  • Sound and the Ear Chapter 2
    © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Chapter© Jones & Bartlett 2 Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Sound and the Ear © Jones Karen &J. Kushla,Bartlett ScD, Learning, CCC-A, FAAA LLC © Jones & Bartlett Learning, LLC Lecturer NOT School FOR of SALE Communication OR DISTRIBUTION Disorders and Deafness NOT FOR SALE OR DISTRIBUTION Kean University © Jones & Bartlett Key Learning, Terms LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR Acceleration DISTRIBUTION Incus NOT FOR SALE OR Saccule DISTRIBUTION Acoustics Inertia Scala media Auditory labyrinth Inner hair cells Scala tympani Basilar membrane Linear scale Scala vestibuli Bel Logarithmic scale Semicircular canals Boyle’s law Malleus Sensorineural hearing loss Broca’s area © Jones & Bartlett Mass Learning, LLC Simple harmonic© Jones motion (SHM) & Bartlett Learning, LLC Brownian motion Membranous labyrinth Sound Cochlea NOT FOR SALE OR Mixed DISTRIBUTION hearing loss Stapedius muscleNOT FOR SALE OR DISTRIBUTION Compression Organ of Corti Stapes Condensation Osseous labyrinth Tectorial membrane Conductive hearing loss Ossicular chain Tensor tympani muscle Decibel (dB) Ossicles Tonotopic organization © Jones Decibel & hearing Bartlett level (dB Learning, HL) LLC Outer ear © Jones Transducer & Bartlett Learning, LLC Decibel sensation level (dB SL) Outer hair cells Traveling wave theory NOT Decibel FOR sound SALE pressure OR level DISTRIBUTION
    [Show full text]
  • Stereocilia Rootlets: Actin-Based Structures That Are Essential for Structural Stability of the Hair Bundle
    International Journal of Molecular Sciences Review Stereocilia Rootlets: Actin-Based Structures That Are Essential for Structural Stability of the Hair Bundle Itallia Pacentine, Paroma Chatterjee and Peter G. Barr-Gillespie * Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; [email protected] (I.P.); [email protected] (P.C.) * Correspondence: [email protected]; Tel.: +1-503-494-2936 Received: 12 December 2019; Accepted: 1 January 2020; Published: 3 January 2020 Abstract: Sensory hair cells of the inner ear rely on the hair bundle, a cluster of actin-filled stereocilia, to transduce auditory and vestibular stimuli into electrical impulses. Because they are long and thin projections, stereocilia are most prone to damage at the point where they insert into the hair cell’s soma. Moreover, this is the site of stereocilia pivoting, the mechanical movement that induces transduction, which additionally weakens this area mechanically. To bolster this fragile area, hair cells construct a dense core called the rootlet at the base of each stereocilium, which extends down into the actin meshwork of the cuticular plate and firmly anchors the stereocilium. Rootlets are constructed with tightly packed actin filaments that extend from stereocilia actin filaments which are wrapped with TRIOBP; in addition, many other proteins contribute to the rootlet and its associated structures. Rootlets allow stereocilia to sustain innumerable deflections over their lifetimes and exemplify the unique manner in which sensory hair cells exploit actin and its associated proteins to carry out the function of mechanotransduction. Keywords: rootlet; actin; stereocilia; hair cell 1. Introduction Eukaryotic cells use actin as a basic building block of the cytoskeleton.
    [Show full text]
  • Nomina Histologica Veterinaria, First Edition
    NOMINA HISTOLOGICA VETERINARIA Submitted by the International Committee on Veterinary Histological Nomenclature (ICVHN) to the World Association of Veterinary Anatomists Published on the website of the World Association of Veterinary Anatomists www.wava-amav.org 2017 CONTENTS Introduction i Principles of term construction in N.H.V. iii Cytologia – Cytology 1 Textus epithelialis – Epithelial tissue 10 Textus connectivus – Connective tissue 13 Sanguis et Lympha – Blood and Lymph 17 Textus muscularis – Muscle tissue 19 Textus nervosus – Nerve tissue 20 Splanchnologia – Viscera 23 Systema digestorium – Digestive system 24 Systema respiratorium – Respiratory system 32 Systema urinarium – Urinary system 35 Organa genitalia masculina – Male genital system 38 Organa genitalia feminina – Female genital system 42 Systema endocrinum – Endocrine system 45 Systema cardiovasculare et lymphaticum [Angiologia] – Cardiovascular and lymphatic system 47 Systema nervosum – Nervous system 52 Receptores sensorii et Organa sensuum – Sensory receptors and Sense organs 58 Integumentum – Integument 64 INTRODUCTION The preparations leading to the publication of the present first edition of the Nomina Histologica Veterinaria has a long history spanning more than 50 years. Under the auspices of the World Association of Veterinary Anatomists (W.A.V.A.), the International Committee on Veterinary Anatomical Nomenclature (I.C.V.A.N.) appointed in Giessen, 1965, a Subcommittee on Histology and Embryology which started a working relation with the Subcommittee on Histology of the former International Anatomical Nomenclature Committee. In Mexico City, 1971, this Subcommittee presented a document entitled Nomina Histologica Veterinaria: A Working Draft as a basis for the continued work of the newly-appointed Subcommittee on Histological Nomenclature. This resulted in the editing of the Nomina Histologica Veterinaria: A Working Draft II (Toulouse, 1974), followed by preparations for publication of a Nomina Histologica Veterinaria.
    [Show full text]
  • 36 | Sensory Systems 1109 36 | SENSORY SYSTEMS
    Chapter 36 | Sensory Systems 1109 36 | SENSORY SYSTEMS Figure 36.1 This shark uses its senses of sight, vibration (lateral-line system), and smell to hunt, but it also relies on its ability to sense the electric fields of prey, a sense not present in most land animals. (credit: modification of work by Hermanus Backpackers Hostel, South Africa) Chapter Outline 36.1: Sensory Processes 36.2: Somatosensation 36.3: Taste and Smell 36.4: Hearing and Vestibular Sensation 36.5: Vision Introduction In more advanced animals, the senses are constantly at work, making the animal aware of stimuli—such as light, or sound, or the presence of a chemical substance in the external environment—and monitoring information about the organism’s internal environment. All bilaterally symmetric animals have a sensory system, and the development of any species’ sensory system has been driven by natural selection; thus, sensory systems differ among species according to the demands of their environments. The shark, unlike most fish predators, is electrosensitive—that is, sensitive to electrical fields produced by other animals in its environment. While it is helpful to this underwater predator, electrosensitivity is a sense not found in most land animals. 36.1 | Sensory Processes By the end of this section, you will be able to do the following: • Identify the general and special senses in humans • Describe three important steps in sensory perception • Explain the concept of just-noticeable difference in sensory perception Senses provide information about the body and its environment. Humans have five special senses: olfaction (smell), gustation (taste), equilibrium (balance and body position), vision, and hearing.
    [Show full text]
  • Ultrastructural Analysis and ABR Alterations in the Cochlear Hair-Cells Following Aminoglycosides Administration in Guinea Pig
    Global Journal of Otolaryngology ISSN 2474-7556 Research Article Glob J Otolaryngol Volume 15 Issue 4 - May 2018 Copyright © All rights are reserved by Mohammed A Akeel DOI: 10.19080/GJO.2018.15.555916 Ultrastructural Analysis and ABR Alterations in the Cochlear Hair-cells Following Aminoglycosides Administration in Guinea Pig Mohammed A Akeel* Department of Anatomy, Faculty of Medicine, Jazan University, Jazan, Kingdom of Saudi Arabia Submission: April 18, 2018; Published: May 08, 2018 *Corresponding author: Mohammed A Akeel, Faculty of Medicine, Jazan University, P.O.Box 114, Jazan, Kingdom of Saudi Arabia. Tel: ; Email: Abstract Aims: since their introduction in the 1940. The aim of the present work was to characterize ultrastructural alterations of the sensory hair-cell following different aminoglycosides Aminoglycosides administration, (AG) antibiotics intratympanic were the first VS ototoxic intraperitoneal agents to and highlight to correlate the problem them with of drug-induced auditory brainstem hearing responses and vestibular (ABR). loss, Methods: streptomycin, gentamycin, or netilmicin; respectively, via the peritoneal route. The next four groups received similar treatment via trans- tympanic route. A Thetotal treatment of 48 adult was guinea administered pigs were dividedfor seven into consecutive 8 groups; sixdays. animals On day in 10,each ABR group. was The utilized first fourfor hearing groups receivedevaluation saline and (control),scanning electron microscopy (SEM) examination of the sensory organs was used for morphological study. Results: Streptomycin produced the most severe morphological changes and a higher elevation of ABR thresholds, followed, in order, by gentamycin and netilmicin. Netilmicin ototoxicity observed in both systemic and transtympanic routes was low because of lesser penetration into the inner ear or/ and lower intrinsic toxicity.
    [Show full text]
  • The Tectorial Membrane of the Rat'
    The Tectorial Membrane of the Rat’ MURIEL D. ROSS Department of Anatomy, The University of Michigan, Ann Arbor, Michigan 48104 ABSTRACT Histochemical, x-ray analytical and scanning and transmission electron microscopical procedures have been utilized to determine the chemical nature, physical appearance and attachments of the tectorial membrane in nor- mal rats and to correlate these results with biochemical data on protein-carbo- hydrate complexes. Additionally, pertinent histochemical and ultrastructural findings in chemically sympathectomized rats are considered. The results indi- cate that the tectorial membrane is a viscous, complex, colloid of glycoprotein( s) possessing some oriented molecules and an ionic composition different from either endolymph or perilymph. It is attached to the reticular laminar surface of the organ of Corti and to the tips of the outer hair cells; it is attached to and encloses the hairs of the inner hair cells. A fluid compartment may exist within the limbs of the “W’formed by the hairs on each outer hair cell surface. Present biochemical concepts of viscous glycoproteins suggest that they are polyelectro- lytes interacting physically to form complex networks. They possess character- istics making them important in fluid and ion transport. Furthermore, the macro- molecular configuration assumed by such polyelectrolytes is unstable and subject to change from stress or shifts in pH or ions. Thus, the attachments of the tec- torial membrane to the hair cells may play an important role in the transduction process at the molecular level. The present investigation is an out- of the tectorial membrane remain matters growth of a prior study of the effects of of dispute.
    [Show full text]
  • A Role for Tectorial Membrane Mechanics in Activating the Cochlear Amplifer Amir Nankali1, Yi Wang4, Clark Elliott Strimbu4, Elizabeth S
    www.nature.com/scientificreports OPEN A role for tectorial membrane mechanics in activating the cochlear amplifer Amir Nankali1, Yi Wang4, Clark Elliott Strimbu4, Elizabeth S. Olson3,4 & Karl Grosh1,2* The mechanical and electrical responses of the mammalian cochlea to acoustic stimuli are nonlinear and highly tuned in frequency. This is due to the electromechanical properties of cochlear outer hair cells (OHCs). At each location along the cochlear spiral, the OHCs mediate an active process in which the sensory tissue motion is enhanced at frequencies close to the most sensitive frequency (called the characteristic frequency, CF). Previous experimental results showed an approximate 0.3 cycle phase shift in the OHC-generated extracellular voltage relative the basilar membrane displacement, which was initiated at a frequency approximately one-half octave lower than the CF. Findings in the present paper reinforce that result. This shift is signifcant because it brings the phase of the OHC-derived electromotile force near to that of the basilar membrane velocity at frequencies above the shift, thereby enabling the transfer of electrical to mechanical power at the basilar membrane. In order to seek a candidate physical mechanism for this phenomenon, we used a comprehensive electromechanical mathematical model of the cochlear response to sound. The model predicts the phase shift in the extracellular voltage referenced to the basilar membrane at a frequency approximately one-half octave below CF, in accordance with the experimental data. In the model, this feature arises from a minimum in the radial impedance of the tectorial membrane and its limbal attachment. These experimental and theoretical results are consistent with the hypothesis that a tectorial membrane resonance introduces the correct phasing between mechanical and electrical responses for power generation, efectively turning on the cochlear amplifer.
    [Show full text]
  • VESTIBULAR SYSTEM (Balance/Equilibrium) the Vestibular Stimulus Is Provided by Earth's Gravity, and Head/Body Movement. Locate
    VESTIBULAR SYSTEM (Balance/Equilibrium) The vestibular stimulus is provided by Earth’s gravity, and head/body movement. Located in the labyrinths of the inner ear, in two components: 1. Vestibular sacs - gravity & head direction 2. Semicircular canals - angular acceleration (changes in the rotation of the head, not steady rotation) 1. Vestibular sacs (Otolith organs) - made of: a) Utricle (“little pouch”) b) Saccule (“little sac”) Signaling mechanism of Vestibular sacs Receptive organ located on the “floor” of Utricle and on “wall” of Saccule when head is in upright position - crystals move within gelatinous mass upon head movement; - crystals slightly bend cilia of hair cells also located within gelatinous mass; - this increases or decreases rate of action potentials in bipolar vestibular sensory neurons. Otoconia: Calcium carbonate crystals Gelatinous mass Cilia Hair cells Vestibular nerve Vestibular ganglion 2. Semicircular canals: 3 ring structures; each filled with fluid, separated by a membrane. Signaling mechanism of Semicircular canals -head movement induces movement of endolymph, but inertial resistance of endolymph slightly bends cupula (endolymph movement is initially slower than head mvmt); - cupula bending slightly moves the cilia of hair cells; - this bending changes rate of action potentials in bipolar vestibular sensory neurons; - when head movement stops: endolymph movement continues for slightly longer, again bending the cupula but in reverse direction on hair cells which changes rate of APs; - detects “acceleration”
    [Show full text]
  • Anatomic Moment
    Anatomic Moment Hearing, I: The Cochlea David L. Daniels, Joel D. Swartz, H. Ric Harnsberger, John L. Ulmer, Katherine A. Shaffer, and Leighton Mark The purpose of the ear is to transform me- cochlear recess, which lies on the medial wall of chanical energy (sound) into electric energy. the vestibule (Fig 3). As these sound waves The external ear collects and directs the sound. enter the perilymph of the scala vestibuli, they The middle ear converts the sound to fluid mo- are transmitted through the vestibular mem- tion. The inner ear, specifically the cochlea, brane into the endolymph of the cochlear duct, transforms fluid motion into electric energy. causing displacement of the basilar membrane, The cochlea is a coiled structure consisting of which stimulates the hair cell receptors of the two and three quarter turns (Figs 1 and 2). If it organ of Corti (Figs 4–7) (4, 5). It is the move- were elongated, the cochlea would be approxi- ment of hair cells that generates the electric mately 30 mm in length. The fluid-filled spaces potentials that are converted into action poten- of the cochlea are comprised of three parallel tials in the auditory nerve fibers. The basilar canals: an outer scala vestibuli (ascending spi- membrane varies in width and tension from ral), an inner scala tympani (descending spi- base to apex. As a result, different portions of ral), and the central cochlear duct (scala media) the membrane respond to different auditory fre- (1–7). The scala vestibuli and scala tympani quencies (2, 5). These perilymphatic waves are contain perilymph, a substance similar in com- transmitted via the apex of the cochlea (helico- position to cerebrospinal fluid.
    [Show full text]
  • Physiology of the Inner Ear Balance
    § Te xt § Important Lecture § Formulas No.15 § Numbers § Doctor notes “Life Is Like Riding A § Notes and explanation Bicycle. To Keep Your Balance, You Must Keep Moving” 1 Physiology of the inner ear balance Objectives: 1. Understand the sensory apparatus of the inner ear that helps the body maintain its postural equilibrium. 2. The mechanism of the vestibular system for coordinating the position of the head and the movement of the eyes. 3. The function of semicircular canals (rotational movements, angular acceleration). 4. The function of the utricle and saccule within the vestibule (respond to changes in the position of the head with respect to gravity (linear acceleration). 5. The connection between the vestibular system and other structure (eye, cerebellum, brain stem). 2 Control of equilibrium } Equilibrium: Reflexes maintain body position at rest & movement through receptors of postural reflexes: 1. Proprioceptive system (Cutaneous sensations). 2. Visual (retinal) system. 3. Vestibular system (Non auditory membranous labyrinth1). 4. Cutaneous sensation. } Cooperating with vestibular system wich is present in the semicircular canals in the inner ear. 3 1: the explanation in the next slide. • Ampulla or crista ampullaris: are the dilations at the end of the semicircular canals and they affect the balance. • The dilations connect the semicircular canals to the cochlea utricle Labyrinth and saccule: contain the vestibular apparatus (maculla). Bony labyrinth • bony cochlea, vestibule & 3 bony semicircular canals. • Enclose the membranous labyrinth. Labyrinth a. Auditory (cochlea for hearing). b. Non-auditory for equilibrium (Vestibular apparatus). composed of two parts: • Vestibule: (Utricle and Saccule). • Semicircular canals “SCC”. Membranous labyrinth • Membranous labyrinth has sensory receptors for hearing and equilibrium • Vestibular apparatus is responsible for equilibrium 4 Macula (otolith organs) of utricle and saccule } Hair cell synapse with endings of the vestibular nerve.
    [Show full text]
  • The Nervous System: General and Special Senses
    18 The Nervous System: General and Special Senses PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska © 2012 Pearson Education, Inc. Introduction • Sensory information arrives at the CNS • Information is “picked up” by sensory receptors • Sensory receptors are the interface between the nervous system and the internal and external environment • General senses • Refers to temperature, pain, touch, pressure, vibration, and proprioception • Special senses • Refers to smell, taste, balance, hearing, and vision © 2012 Pearson Education, Inc. Receptors • Receptors and Receptive Fields • Free nerve endings are the simplest receptors • These respond to a variety of stimuli • Receptors of the retina (for example) are very specific and only respond to light • Receptive fields • Large receptive fields have receptors spread far apart, which makes it difficult to localize a stimulus • Small receptive fields have receptors close together, which makes it easy to localize a stimulus. © 2012 Pearson Education, Inc. Figure 18.1 Receptors and Receptive Fields Receptive Receptive field 1 field 2 Receptive fields © 2012 Pearson Education, Inc. Receptors • Interpretation of Sensory Information • Information is relayed from the receptor to a specific neuron in the CNS • The connection between a receptor and a neuron is called a labeled line • Each labeled line transmits its own specific sensation © 2012 Pearson Education, Inc. Interpretation of Sensory Information • Classification of Receptors • Tonic receptors
    [Show full text]
  • Stiffness and Tension Gradients of the Hair Cell's Tip-Link Complex In
    RESEARCH ARTICLE Stiffness and tension gradients of the hair cell’s tip-link complex in the mammalian cochlea Me´ lanie Tobin1,2, Atitheb Chaiyasitdhi1,2†, Vincent Michel2,3,4†, Nicolas Michalski2,3,4, Pascal Martin1,2* 1Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France; 2Sorbonne Universite´, Paris, France; 3Laboratoire de Ge´ne´tique et Physiologie de l’Audition, Institut Pasteur, Paris, France; 4UMRS 1120, Institut National de la Sante´ et de la Recherche Me´dicale (INSERM), Paris, France Abstract Sound analysis by the cochlea relies on frequency tuning of mechanosensory hair cells along a tonotopic axis. To clarify the underlying biophysical mechanism, we have investigated the micromechanical properties of the hair cell’s mechanoreceptive hair bundle within the apical half of the rat cochlea. We studied both inner and outer hair cells, which send nervous signals to the brain and amplify cochlear vibrations, respectively. We find that tonotopy is associated with gradients of stiffness and resting mechanical tension, with steeper gradients for outer hair cells, emphasizing the division of labor between the two hair-cell types. We demonstrate that tension in the tip links that convey force to the mechano-electrical transduction channels increases at reduced Ca2+. Finally, we reveal gradients in stiffness and tension at the level of a single tip link. We conclude that mechanical gradients of the tip-link complex may help specify the characteristic frequency of the hair cell. DOI: https://doi.org/10.7554/eLife.43473.001 *For correspondence: [email protected] †These authors contributed equally to this work Introduction The cochlea—the auditory organ of the inner ear—is endowed with a few thousands of mechanosen- Competing interests: The sory hair cells that are each tuned to detect a characteristic sound frequency (Fettiplace and Kim, authors declare that no 2014).
    [Show full text]