Question

1. Describe the process of audition, following a sound wave from the outer ear through the middle ear and into the inner ear. How are auditory neurons ultimately activated?

2.Describe the pathway of auditory nerve signals from the auditory nerve to primary auditory cortex.

3. Describe both conductive and sensorineural hearing loss and why they occur. Can they be treated?

Answer 1

1. The ear has three main parts- External ear ( receive sound waves room external environment and convey to the middle ear), Middle ear (form sound vibrations and convey to the inner ear), and inner ear ( receptors and auditory pathways are activated).

The physiology of hearing (audition)

External ear

a. Auricle of the external ear convey sound waves into external auditory canal

b. This sound waves strike tympanic membrane and it vibrates back and forth. Following this eardrum vibrates

Middle ear

c. Malleus (muscle) is connected with central area of the eardrum. other end of malleus is connected to the incus (muscle) and incus is connected with stapes (muscle)When eardrum vibrates Malleus and vibrations are transmitted to incus and stapes.

d. When stapes vibrates back and forth it also pushes oval window - oval window start vibrating more vigorously (20 times more than eardrum)

Internal ear

e. The vibration of oval window creates waves in the perilymph of the cochlea and scala vestibuli

f. This waves transmits from scala vestibuli to the scala tympani then reaches to the round window.

g. Pressure awes in the scala vestibuli and tympani vibrates vestibular membrane back and forth- which produce an pressure waves in the endolymph of the cochlear duct.

h. Pressure waves in the endolymph of cochlear duct vibrate basilar membrane - causes bending of hair cell stereocilia- stimulates receptors - and produces receptors potential. - leads to activation of auditory neuron and propagation of nerve impulses