Fluid in the Ear

An Interrupted Case in Auditory Physiology

Co Authors:	Jason W. Ho Department of Biology Villanova University Scott M. Leighow Department of Biology Villanova University Sylvie Lee Department of Biology Villanova University Philip J. Stephens Department of Biology Villanova University phil.stephens@villanova.edu
Abstract:	This interrupted case study follows the progress of Julius, a singer in a rock band who suffers from severe headaches and pressure in his ears. While visiting his doctor he loses his balance and hits his head as he collapses to the floor. Julius recovers enough to realize that he has lost his hearing and is then taken to the hospital. The story is further developed in order to guide students in exploring the anatomy of the inner ear, the roles of perilymph and endolymph, and the effect of Meniere's disease on the ability to hear. The case has been used in one-semester courses in animal physiology and neurobiology, but could also be used in an anatomy and physiology course. The case is best delivered when covering the topics of hearing and balance, and could easily be expanded to review membrane potentials, action potentials, concentration gradients, types of channels, influence of blood pressure on filtration/reabsorption dynamics at capillaries, etc.
Objectives:	Describe how sound stimulates hair cells in the cochlea. Recognize the difference between endolymph and perilymph. Describe where endolymph is secreted in the cochlea and into the circulatory system through the endolymphatic sac. Recognize that Meniere's disease can be caused by an inflammation of the endolymphatic duct. Describe how damage to the vestibular membrane can cause mixing of the endolymph and the perilymph and decrease the level of potassium that bathes the stereocilia of the hair cells. Describe how opening potassium channels can depolarize the hair cells and produce action potentials in the sensory nerves. Explain how a decrease in the level of potassium bathing the stereocilia can reduce the amount of hair cell depolarization, neurotransmitter secretion, and stimulation of the sensory neurons.
Keywords:	Ear; hearing; balance; perilymph; endolymph; Meniere’s disease; potassium; endolymphatic sac; cochlea; action potential
Topical Area:	N/A
Educational Level:	Undergraduate lower division, Undergraduate upper division
Formats:	PDF
Type/Method:	Interrupted
Language:	English
Subject Headings:	Biology (General) Physiology Medicine (General) Neuroscience
Date Posted:	4/24/2018
Date Modified:	N/A
Copyright:	Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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