12.16.4 The Ear and Hearing

Question 1

The Ear and Hearing

Answer 1

• Review: All sense organs, including hearing, smell, vision, and taste, operate on the cellular level through biochemical reactions.
• The basic mechanism by which hearing occurs is as follows:
· The pinna of the ear channels air vibrations, or sound, down the outer ear to the tympanic membrane.
· The middle ear contains three bones, the malleus, incus, and stapes, which conduct and amplify sound vibrations.
· In the inner ear, vibrations travel through fluid that fills the coils of the cochlea, which results in vibrations of the basilar membrane. The organ of Corti, located
in the basilar membrane, converts the vibrations into nerve impulses.

Question 2

note

Answer 2

• Like other sense organs, the process of hearing sounds involves the translation of an environmental stimulus to a nerve impulse.
• Sounds enter the ear via the pinna (the structure commonly thought of as the ear), which channels the air vibrations to the tympanic membrane of the middle ear.
• Once the air vibrations reach the tympanic membrane, it sequentially vibrates the malleus, incus, and stapes, the three bones of the middle ear. The vibrations then move into the inner ear. The inner ear is filled with fluid, and the sound vibration now travels through a liquid medium.
• High frequency waves travel through the middle and inner ear at a high number of cycles per unit of time. Low frequency waves travel at a low number of cycles per unit of time. The frequency of a particular wavelength is translated into sound in the cochlea.
• The diagram of the uncoiled cochlea on the left shows how high and low frequency vibrations are translated into sound. Vibrations travel through the fluid-filled cochlea and cause reverberations along the basilar membrane. A high frequency vibration will cause a deflection along a different point of the membrane than a low frequency vibration will.
• A structure inside of the basilar membrane called the Organ of Corti contains hair cells, which detect vibrations. The hair cells transmit the signal to neurons, which rely the information to the brain.

Question 3

Soundwaves are transformed into action potentials

Answer 3

• as hair cells are bent by the tectorial membrane

Question 4

True or false?

Pitch is a function of the amplitude of a sound wave.

Answer 4

• false

Question 5

The _______________ is the outside part of the ear that can be seen.

Answer 5

• pinna

Question 6

The eardrum is also known as the _______________ membrane

Answer 6

• tympanic

Question 7

Low frequency sounds are detected at the

Answer 7

• distal end of the cochlea, near the tip of the cochlear duct