4. The cochlea is the place where sound energy is converted into neural impulses—a process called transduction.
The neural impulses flow out of the cochlea, through the auditory nerve on the way toward the brain.
Name the major structures of the auditory system.
Understand the role of each auditory system structure in transmitting auditory information.
Review
1. How does the ear transform sound waves into nerve impulses that our brain can understand?
When a sound wave reaches our head, the pinna (external portion of the outer ear) funnels the sound through the auditory canal to the eardrum.
Review
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2. The alternating bands, or regions, of high and low pressure in the sound wave cause the eardrum to vibrate at the same rate as the object that produced the sound wave.
Vibrations of the eardrum pass through the three small middle ear bones, which serve as a sort of primitive amplifier to intensify the vibrations. When the vibrations reach the cochlea (a snail-shaped tube in the inner ear), they jostle the fluid that fills the tube.
Review
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3. The movement of the fluid within the cochlea bends the tiny hair cells on the basilar membrane. This causes the hair cells to release neurotransmitters.
The greater the intensity of the sound, the more the hair cells are bent, and then more neurotransmitters are released.
Review
4. The cochlea is the place where sound energy is converted into neural impulses—a process called transduction.
The neural impulses flow out of the cochlea, through the auditory nerve on the way toward the brain.
Review
5. The neural impulses from the cochlea pass through the auditory nerve to the thalamus—the relay station for the senses—in the center of the brain.
From there they are relayed on to the auditory cortex (in the temporal lobe of each brain hemisphere) for further processing and interpretation.
Most of the signals from the left ear cross over to the auditory area in the right hemisphere, but a small portion of the signals goes directly to the auditory area of the left hemisphere. The reverse is true for the right ear.
As a result, most of the information contained in the sound wave ends its journey in the hemisphere opposite the ear that detected the sound.
Quiz 1
Quiz 2