Cell Damage in the Ear

 

The Outer Hair Cells - Inner Ear Prisms


The outer hair cells (there are three rows) act as tiny inner ear amplifiers, and more specifically, act in pitch discrimination.  The visual equivalent would be having a built-in prism in the ear separating sound frequencies from noise.   Interestingly, the human eye cannot pick out individual frequencies in “white light” the same way the outer hair cells allow the ear to pick out frequencies in sound.


As you might expect, that is a very sensitive function built-in to the ear.  It is unfortunately not reparable once it is damaged.
















Noise Damage


Remember the inner ear is an organ with some delicate features, such as the “prism” function.  Exposing the

ear to excessive levels of damaging noise (examples:  music, MP3, industrial sources, engine rooms) is the

same as using a delicate instrument like a jeweller’s screwdriver to open a can of paint.  That instrument becomes dull and useless when used inappropriately to perform gross functions on a repeated basis.

Figure A: Normal outer and inner hair cells in the Organ of Corti. Note three rows of outer hair cells; these act as tiny inner ear amplifiers, and more specifically, act in pitch discrimination. That is a specialized function that allows a person to pick out one frequency of sound among many. The best example is a person’s ability to make out a conversation in a noisy environment.

Robert Preston and Joseph Hawkins, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan

Figure B: Damaged outer and inner hair cells of the Organ of Corti. If these cells are damaged across the spectrum of frequencies, then the person develops difficulties understanding speech in noisy environments. Loud noises can cause a VERY large bump in the floor of the organ of Corti. The cells are violently shifted with respect to the tectorial membrane and it essentially tears the hairs from the cells, both inner and outer. This affects how we hear at the affected frequencies (inner cell damage), and how we discriminate frequencies (outer cell damage).
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