TITLE: The physiology of hearing
NAME: Stephanie David, Anatomy and Physiology II, PCC
BACKGROUND- should know the anatomy of the ear : auricle, external auditory canal, eardrum, auditory ossicles, oval window, cochlea, scala vestibuli, scala tympani, and endolymph (I realize that there are more than four that you asked but I think that it is almost impossible to explain this concept if they do not first know the anatomy of the ear)
INTRODUCTION: The problem that I am addressing is the events in stimulation of auditory receptors. This is very important because these are the events that are involved in hearing and hearing is a very, very important sense that we should understand. It is difficult to understand this sense I think because it is very complex compared to the other senses. I found this a difficult concept to understand because it is a long process. What confused me the most is the fact that the organ of Corti is in a spiral and the sound waves loop back near the middle ear.
EXPLANATION: There are many steps in the events of hearing.
1.Of course the first thing to happen is that we receive the sound wave and the auricle does this. The sound wave then goes through the external auditory canal.
2. The sound wave then strikes the eardrum. The intensity of the vibration when hitting the eardrum depends on sound waves.
3. It then passes through the ossicles.
4. After passing the ossicles the sound wave is then pushes the membrane of the oval window in and out.
5. Since there is movement occurring in the oval window it causes fluid pressure waves in the perilymph of the cochlea. Because of the fluid pressure waves the oval window swells inward pushing on the perilymph of the scala vestibuli.
6. Then the sound wave just flows through the scala tympani to the round window and this causes pressure so that it swells outward toward the middle ear.
7. There is then pressure waves in the endolymph inside the cochlear duct because of the pressure waved found within the scala vestibuli and the scala tympani.
8. Since there are pressure waves in the endolymph it causes the basilar membrane to vibrate. This vibration causes hair cells to bend and the bending of these hair cells is very important because it produces nerve impulses by receptor potentials that are produced when these hairs bend.
(There is a great visual found in Tortora on page 552)
SUMMARY: I think that the most important part of this explanation is that the hair cells of the organ of Corti convert a mechanical vibration into a electrical signal which causes nerve impulse. But it is very important to know all the steps. If you really know the anatomy of the ear it should be easy to follow the physiology.