Hearing
In this lesson, we'll explore the auditory system. The cochlea is the main site of sound transduction, where sound waves are converted into neural signals, so that's where we'll start.
1) Start with this video:
2) Then, read these articles:
Know Your Brain - Cochlea
Know Your Brain - Auditory Cortex
3) Watch these videos to learn about tinnitus, a common hearing disorder, and cochlear implants, a remarkable example of neurotechnology:
4) Finally, answer these questions to test your understanding:
1. Which structure or structures transmit vibrations from the eardrum to the cochlea?
- A. hair cells
- B. auditory nerve
- C. basilar membrane
- D. ossicles
Show Answer
Correct answer: D
When sound waves travel through the canal of our ear, they hit the tympanic membrane (eardrum) and cause it to vibrate. This vibration prompts movement in the ossicles, a trio of tiny bones that transmit the vibration to a structure called the oval window, which sits in the wall of the cochlea.
2. Which structure in the cochlea contains the hair cells that convert sound vibrations into neural signals?
- A. tectorial membrane
- B. tympanic membrane
- C. scala vestibuli
- D. organ of Corti
Show Answer
Correct answer: D
The organ of Corti is the receptor organ of the ear. It sits atop the basilar membrane and contains receptor cells known as hair cells, which convert sound vibrations into signals the nervous system can understand.
3. Which lobe of the brain contains the auditory cortex?
- A. frontal
- B. temporal
- C. parietal
- D. occipital
Show Answer
Correct answer: B
The auditory cortex is found in the temporal lobe. Most of it is hidden from view, buried deep within a fissure called the lateral sulcus. Some auditory cortex is visible on the external surface the brain, however, as it extends to a gyrus called the superior temporal gyrus.
4. Which of the following is an accepted mechanism underlying tinnitus?
- A. cochlear damage causing compensatory hyperactivity in auditory pathways
- B. complete loss of activity in the auditory cortex
- C. excessive earwax directly stimulating auditory nerve firing
- D. increased blood flow to the cochlea producing phantom sounds
Show Answer
Correct answer: A
The mechanisms underlying tinnitus are not well understood, but it’s thought that hearing loss might be linked to tinnitus in a number of ways. Damage to the cochlea, for example, may lead to increased signaling in other auditory structures to compensate for the reduction in auditory input from the cochlea, and the resultant amplification of neural noise may lead to tinnitus.
5. How does a cochlear implant improve hearing in someone who is deaf or has severe hearing loss?
- A. it causes vibration of the eardrum to create the sensation of sound
- B. it enhances auditory processing through stimulation of brainstem nuclei
- C. it amplifies existing sound waves so they are loud enough to detect
- D. it stimulates the auditory nerve to send auditory information to the brain
Show Answer
Correct answer: D
Cochlear implants involve a microphone that detects sound, as well as a sound processor that converts the sound into a radio frequency signal. The signal is transmitted to a receiver implanted under the skin behind the ear. The receiver decodes the signal, then converts it into electrical currents. The currents are sent along wires to stimulate the auditory nerve, which sends auditory information to the brain.
