Presbycusis



Presbycusis
Shelley Stewart-Stevens
Brain and Behavior / Week 2
Walden University
March 21, 2010
Doctor Piferi

Presbycusis

Abstract
Presbycusis is the loss of hearing that gradually occurs in most individuals as they grow older. Hearing loss is a common disorder associated with aging. About 30-35 percent of adults between the ages of 65 and 75 years have a hearing loss. It is estimated that 40-50 percent of people 75 and older have a hearing loss. The loss associated with presbycusis is usually greater for high-pitched sounds. For example, it may be difficult for someone to hear the nearby chirping of a bird or the ringing of a telephone. However, the same person may be able to hear clearly the lowpitched sound of a truck rumbling down the street. There are many causes of presbycusis. Most commonly it arises from changes in the inner ear of a person as he or she ages, but presbycusis can also result from changes in the middle ear or from complex changes along the nerve pathways leading to the brain. Presbycusis most often occurs in both ears, affecting them equally. Because the process of loss is gradual, people who have presbycusis may not realize that their hearing is diminishing (Presbycusis, 2002).

Sound Transmission
Sound is transmitted from the environment to the inner ear via the outer, middle, and inner ear. The first step is the pinna must capture the sound and the sound must reach a smaller area, called the auditory canal. The impact of sound hitting the eardrum creates vibrations that cause three bones in the middle ear to move. The malleous (hammer), incus (anvil), and stapes (stirrups). The three bones cause movement of the oval window between the middle and inner ear. When the oval vibrates, fluid in the inner ear transmits the vibrations into the hearing organ, called the cochlea (Mayo, 2010).
In the inner ear, thousands of microscopic hair cells are bent by the wavelike action of fluid inside the cochlea. The bending of these...