What is the Difference Between Inner and Outer Hair Cells?
🆚 Go to Comparative Table 🆚The main difference between inner and outer hair cells lies in their function, innervation, and location within the cochlea. Inner hair cells (IHCs) and outer hair cells (OHCs) are both involved in the process of converting sound waves into electrical signals in the mammalian cochlea, but they have distinct roles and characteristics:
Inner Hair Cells (IHCs):
- Act as sensory receptors, transforming sound vibrations from the fluid in the cochlea into electrical signals.
- Comprise one row of IHCs in humans, with 95% of the fibers of the auditory nerves emerging from this subpopulation towards the brain.
- Have dense innervations.
Outer Hair Cells (OHCs):
- Intensify low-level sounds mechanically entering the fluids of the cochlea.
- Consist of three rows of OHCs in humans.
- Have relatively less dense innervations compared to IHCs.
- Amplify low-level sounds mechanically, with this amplification governed by the movement of the hair bundles.
Furthermore, the outer hair cells are located near the center of the basilar membrane, where vibrations are the greatest, while the basilar membrane is anchored under the inner hair cells.
Comparative Table: Inner vs Outer Hair Cells
The main differences between inner and outer hair cells are their functions, innervations, and their distribution within the cochlea. Here is a tabular comparison of their characteristics:
| Feature | Inner Hair Cells | Outer Hair Cells |
|---|---|---|
| Function | Directly responsible for sending signals to the brain | Involved in the amplification of sounds |
| Innervations | More dense innervations | Less dense innervations |
| Distribution | One row of inner hair cells | Three rows of outer hair cells |
Inner hair cells are the actual sensory receptors, converting sound vibrations from the fluid in the cochlea into electrical signals which are then relayed to the brain via the auditory nerve fibers. On the other hand, outer hair cells amplify low-level sounds mechanically, which are directed towards the cochlea. This amplification is governed by the movement of the hair bundles.
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