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Basilar membrane

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Title: Basilar membrane  
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Subject: Analog ear, Temporal theory (hearing), Inner ear, Sulcus spiralis externus, Cochlear duct
Collection: Auditory System, Ear
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Basilar membrane

Basilar membrane
Section through organ of corti, showing basilar membrane
Cross section of the cochlea.
Latin membrana basilaris ductus cochlearis
MeSH A09.246.631.246.125
Anatomical terminology

The basilar membrane within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani (see figure).


  • Structure 1
  • Function 2
    • Endolymph/perilymph separation 2.1
    • A base for the sensory cells 2.2
    • Frequency dispersion 2.3
  • Additional images 3
  • See also 4
  • References 5
  • External links 6


The basilar membrane is a pseudo-resonant structure[1] that, like strings on an instrument, varies in width and stiffness. The "string" of the basilar membrane is not a set of parallel strings, as in a guitar, but a long structure that has different properties (width, stiffness, mass, damping, and the dimensions of the ducts that it couples to) at different points along its length. The motion of the basilar membrane is generally described as a traveling wave.[2] The parameters of the membrane at a given point along its length determine its characteristic frequency (CF), the frequency at which it is most sensitive to sound vibrations. The basilar membrane is widest (0.42–0.65 mm) and least stiff at the apex of the cochlea, and narrowest (0.08–0.16 mm) and most stiff at the base.[3] High-frequency sounds localize near the base of the cochlea (near the round and oval windows), while low-frequency sounds localize near the apex.


Sinusoidal drive through the oval window (top) causes a traveling wave of fluid–membrane motion. A modeled snapshot of fluid streamlines is shown. The wavelength is long compared to the duct height near the base, in what is called the long-wave region, and short (0.5 to 1.0 mm in typical observations[4][5]) near the place where the displacement and velocity are maximized, just before cutoff, in the short-wave region.

Endolymph/perilymph separation

The fluids in these two tubes, the

  • several animations showing basilar membrane motion under various stimulus conditionsAuditory Neuroscience | The Ear
  • plenty of images, animations, and very concise functional explanationsFunctional anatomy of the inner ear:
  • Video and Scripts to Simulate the Basilar MembraneBasilar Membrane Simulator
  • : good explanation and diagramsThe role of the basilar membrane in sound reception

External links

  1. ^ M. Holmes and J. D. Cole, "Pseudoresonance in the cochlea, ' in: Mechanics of Hearing, E. de Boer and M. A. Viergever (editors), Proceedings of the IUTAM/ICA Symposium, Delft (1983), pp. 45-52.
  2. ^ Richard R. Fay, Arthur N. Popper, and Sid P. Bacon (2004). Compression: From Cochlea to Cochlear Implants. Springer.  
  3. ^ Oghalai JS. The cochlear amplifier: augmentation of the traveling wave within the inner ear. Current Opinion in Otolaryngology & Head & Neck Surgery. 12(5):431-8, 2004
  4. ^ Shera, Christopher A. (2007). "Laser amplification with a twist: Traveling-wave propagation and gain functions from throughout the cochlea". Journal of the Acoustical Society of America 122 (5): 2738–2758.  
  5. ^ Robles, L.; Ruggero, M. A. (2001). "Mechanics of the mammalian cochlea". Physiological Reviews 81 (3): 1305–1352. Retrieved 13 April 2013. 
  6. ^ Salt, A.N., Konishi, T., 1986. The cochlear fluids: Perilymph and endolymph. In: Altschuler, R.A., Hoffman, D.W., Bobbin, R.P. (Eds.), Neurobiology of Hearing: The Cochlea. Raven Press, New York, pp. 109-122
  7. ^ Fritzsch B: The water-to-land transition: Evolution of the tetrapod basilar papilla; middle ear, and auditory nuclei. In: Douglas B. Webster, Richard R. Fay, Arthur N. Popper, editors (1992). The Evolutionary biology of hearing. Berlin: Springer-Verlag. pp. 351–375.  
  8. ^ Schnupp J., Nelken I., King A. (2011). Auditory Neuroscience. Cambridge MA: MIT Press.  
  9. ^ Beament, James (2001). "How We Hear Music: the Relationship Between Music and the Hearing Mechanism". Woodbridge: Boydell Press. p. 97. 
  10. ^ Nilsen KE, Russell IJ (1999). "Timing of cochlear feedback: spatial and temporal representation of a tone across the basilar membrane". Nat. Neurosci. 2 (7): 642–8.  
  11. ^ Nilsen KE, Russell IJ (2000). "The spatial and temporal representation of a tone on the guinea pig basilar membrane". Proc. Natl. Acad. Sci. U.S.A. 97 (22): 11751–8.  


Deiters cells

See also

Additional images

Sound-driven vibrations travel as waves along this membrane, along which, in humans, lie about 3,500 inner hair cells spaced in a single row. Each cell is attached to a tiny triangular frame. The 'hairs' are minute processes on the end of the cell, which are very sensitive to movement. When the vibration of the membrane rocks the triangular frames, the hairs on the cells are repeatedly displaced, and that produces streams of corresponding pulses in the nerve fibers, which are transmitted to the auditory pathway.[9] The outer hair cells feed back energy to amplify the traveling wave, by up to 65 dB at some locations.[10][11]

A third, evolutionarily younger, function of the basilar membrane is strongly developed in the cochlea of most mammalian species and weakly developed in some bird species:[7] the Greenwood function and its variants.

Frequency dispersion

The basilar membrane is also the base for the sensory cells of hearing, the hair cells that are equipped with "Stereocilia". There are approximately 15,000 hair cells in each human ear (see figure). This function as base of the sensory cells gave the basilar membrane its name, and it is again present in all land vertebrates. Due to its location, the basilar membrane places the hair cells in a position where they are adjacent to both the endolymph and the perilymph, which is a precondition of hair cell function.

A base for the sensory cells


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