- The following statements describe the possible functions of the outer hair cells (OHC) of organ of Corti:
A. The outer hair cells (OHC) are depolarized or hyperpolarized depending on the direction of
movement of stereocilia.
B. The OHC are lengthened in depolarization and shortened in hyperpolarization
C. The OHC decrease the amplitude and clarity of sound by shortening and lengthening.
D. The efferent nerve fibers of olivocochlear bundle modulate the sensitivity of the OHC
E. The effect of stimulation of olivocochlear bundle on the OHC is excitatory.
Which one of the options given below represents the correct statements?
(1) A and B (2) C and D
(3) A and D (4) D and E
The outer hair cells (OHCs) of the organ of Corti play a critical role in the mammalian auditory system by enhancing sound sensitivity, frequency selectivity, and dynamic range. Their unique characteristics, such as changing length in response to electrical signals and interaction with efferent nerve fibers, distinguish them functionally from inner hair cells.
Functions and Properties of Outer Hair Cells
Electrical Response to Stereocilia Movement (Statement A)
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Outer hair cells depolarize or hyperpolarize depending on the direction of stereocilia deflection.
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Deflection toward the tallest stereocilia increases tension on tip links, opens ion channels, and causes depolarization.
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Deflection in the opposite direction causes hyperpolarization.
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This polarization change influences outer hair cell activity and auditory sensitivity.ncbi.nlm.nih+1
Electromotility: Length Changes During Polarization (Statement B)
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Prestin, a motor protein in OHC membranes, causes these cells to shorten on depolarization and lengthen on hyperpolarization.
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This electromotility changes the mechanical properties of the cochlear partition, particularly the basilar membrane vibration.biologyinsights+1
Sound Amplification, not Decreasing Amplitude (Statement C)
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Contrary to statement C, the OHCs increase the amplitude and clarity of sound by amplifying basilar membrane movement via their length changes.
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They actively enhance cochlear tuning and frequency discrimination rather than reducing sound clarity.ncbi.nlm.nih+1
Modulation by Olivocochlear Bundle (Statements D and E)
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The efferent olivocochlear bundle innervates OHCs and modulates their sensitivity to sound stimuli.
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Activation typically inhibits or modulates OHC electromotility, protecting the cochlea from damage and adjusting sensitivity under different acoustic environments.
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The effect on OHCs is generally inhibitory, not excitatory, contradicting statement E.biologyinsights+1
Analysis of the Statements
Statement Content Correctness A OHC depolarized or hyperpolarized based on stereocilia movement direction Correct B OHC lengthened in hyperpolarization, shortened in depolarization Correct C OHC decrease amplitude and clarity of sound by changing length Incorrect D Olivocochlear efferents modulate OHC sensitivity Correct E Olivocochlear stimulation of OHC is excitatory Incorrect Correct Option
Among the options, the set of correct statements is A and D, making:
(3) A and D
the correct answer.
Conclusion
Outer hair cells enhance auditory perception through voltage-driven length changes and interaction with efferent neurons from the olivocochlear bundle, which fine-tunes cochlear sensitivity. They serve as mechanical amplifiers, improving sound clarity and frequency resolution, and participate in auditory protection by modulation through efferent pathways.
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