Organ of corti
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Organ of Corti. Organ of Corti (limbus). Organ of Corti (tectorial memb.). Organ of Corti (inner hair cells). Organ of Corti (outer hair cells). Organ of Corti (spriral lamina). Organ of Corti (habenula perforata). Organ of Corti (supporting cells). Organ of Corti (basilar membrane).

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Organ of Corti

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Organ of Corti


Organ of Corti (limbus)


Organ of Corti (tectorial memb.)


Organ of Corti (inner hair cells)


Organ of Corti (outer hair cells)


Organ of Corti (spriral lamina)


Organ of Corti (habenula perforata)


Organ of Corti (supporting cells)


Organ of Corti (basilar membrane)


Organ of Corti (VIIIth nerve)


More on Cells

  • Hair Cells

    • Outer Hair Cells

    • Inner Hair Cells

  • Supporting Cells (modiolus to stria vascularis)

    • Vestibular Lip

    • Border Cells of Held

    • Inner Phalangeal Cells

    • Rods of Corti (Pillar Cells)

    • Dieters Cells

    • Hensons Cells

    • Claudius and Boettcher Cells


Insert zemlin page 471


Cross section showing hair cells and supporting cells

  • Note: modiolus is to the right of slide


Inner Hair Cells

  • Inner Hair Cells (see previous slide)

    • Jug shaped

    • Larger than OHCs

    • Single Row

    • 3000 to 4000 in number

    • Innervated by both afferent and efferent fibers

  • IHC cilia

    • 50 to 70 cilia per cell in U shaped configuration.

    • Cilia not embedded in tectorial membrane


Outer Hair Cells

  • Outer Hair Cells (see previous slide)

    • Tube shaped

    • Smaller than IHCs

    • 3 rows except at apical end where it increases to 4 and then 5 rows

    • 12,000 to 13,000 in number

    • Innervated by both afferent and efferent fibers

  • OHC cilia

    • 58 cilia at apical end to 150 per cell at basal end in W or V shaped configuration.

    • Cilia embedded in tectorial membrane


Cilia

  • Photo showing U shaped configuration of IHC (top) and W or V shaped configuration of OHC (bottom)


Hair Cell Structures


Hair Cell (stereocilia)


Hair Cell (dendrite)


Hair Cell (synaptic cleft)


Hair Cell (cuticle)


Hair Cell (reticular lamina)


Hair Cell (photo)

  • Outer Hair cells showing the stereocilia, reticular lamina and cuticle.


Hair Cell (efferent axon)


Cross-section of the auditory nerve


Auditory Nerve Fiber Bundle

High frequency fibers: outer auditory nerve

Low frequency fibers: inner auditory nerve

Tonotopicity in the auditory nerve

Mapping of frequency to place along the basilar

membrane preserved in central auditory nervous system

fiber CF

200

500

1000

Hair cells

Apex: wide and loose

Basilar membrane

Base: narrow and tight


Auditory Pathways


Auditory Pathways


Auditory Pathways


Effects of decusation


Central auditory system

StructureFunction/Description

IHC to Auditory Nerve Fiber1st synapse located in the cochlea

Cochlear Nucleus2nd synapse (1st central way station)

Superior Olivary Complex3rd synapse, Convergence of inputs from two ears, Delay line, localization

Inferior Colliculi4th synapse, multi-sensory integration

Medial Geniculate Body5th synapse, located in the thalamus

Auditory Cortex6th synapse


Sagittal view of the brain


Primary auditory cortex is tonotopically organized


fiber CF

8000 Hz

4000

2000

fiber CF

200

500

1000

fiber CF

8000 Hz

4000

3000

fiber CF

200

500

700

Plasticity: flexibility,

the ability to adapt to

new situations.

Tonotopically organized

Auditory Cortex

Normal

Hair cell death, 1-2 kHz


Central auditory pathways: review


Acoustic Reflex Arc

  • Acoustic reflex:

  • Contraction of the stapedius and tensor tympani muscles occurs at high intensity levels

  • The response is bilateral

  • Some functions:

    • Protection from intense sounds

    • Smoothing of the frequency response of the outer and middle ears


Acoustic Reflex Arc

Midline of the brain

Efferent

(ipsilateral pathway)

Efferent

(contralateral pathway)

STIMULUS

Afferent


Inner Ear Fluids


Blood Supply


Summary


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