CNS/Sensory VI Flashcards
What is sound?
Pressure waves moving past your head.
What does the amplitude of a sound wave correspond to?
Its loudness.
What does the frequency of sound correspond to?
The number of cycles per second, which indicates pitch.
What is the normal audibility curve?
It depicts the relationship between how you perceive sound and the frequency of the sound waves (pitch) + the loudness of the sound (amplitude).
What is the formula for a dB?
dB = 20 log (sound pressure / reference pressure)
Going from 20 dB to 60 dB means that the sound amplitude has gotten […] times larger. Explain why.
100 X, since every 20 dB equals 10 X more.
How does the damage threshold differ from the pain threshold?
The pain threshold exists above the damage threshold, meaning that you can damage your hearing without necessarily feeling pain.
What frequency range do humans hear best?
100 to 10,000 Hz
What is the damage threshold for audibility?
Around 85 dB
What is the pain threshold for audibility?
At low frequencies, around 160 dB and within our typical audible range, around 130-140 dB.
Why is presbycusis?
It is the gradual loss of the ability to hear high frequency sounds will age.
Describe the major parts of the ear from outside to inside.
Pinna, external auditory canal, tympanic membrane, middle ear (malleus incus and stapes connected to eustachian tube), inner ear (cochlea).
What is the function of the pinna?
It is shaped in order to reflect sound into the ear canal.
What is the function of the eustachian tube?
It connects the middle ear to the throat.
What is the function of the cochlea?
It is where transduction occurs.
Where are the semicircular canals located and what is their function?
They are located in the inner ear. Their function is to encode angular acceleration of the head.
What is the oval window?
It serves as an input to the cochlea.
Where are the sensory epithelia located and what is their function?
They are located in the inner ear as part of the cochlea. They are where neurons are located and where the transduction of ion channels occurs.
Where are the utricle and saccule located and what is their function?
They are located in the inner ear as part of the cochlea. They encode vertical and horizontal acceleration.
Describe the trajectory of sound up to its arrival in the inner ear.
Sound energy will push and pull the tympanic membrane. The membrane is connected to the malleus, incus, and stapes, which are in turn attached to the oval window in the inner ear. When the typanic membrane vibrates, the bones transmit this to the oval window, allowing the energy to reach the inner ear and exert pressure on the cochlear fluid.
What are the three bones in the middle ear and what is their function?
The malleus, incus, and stapes. Their function is to connect the tympanic membrane to the oval window in the inner ear, amplifying the vibrations to the small inner space. This produces a pressure force that can produce vibrations in the fluid of the cochlea in the inner ear.
The movement of the middle ear bones is mediated by […]
Skeletal muscles
How does the activity of the inner ear bones change in a very noisy environment?
The skeletal muscles that modulate the amplification by the inner ear bones will tense so that it takes more energy to move the oval window back and forth. This protects the auditory system.
Where is the round window located and what is its function?
It is located right below the oval window at the boundary between the middle ear and the inner ear. It moves opposite to the movement of the oval window (moves out when the OW moves in and vice versa). This helps cochlear fluid move in the inner ear.
Explain how sound energy travels once it has gotten into the inner ear.
The movement of the oval and round windows allows for the vibrations to travel through the cochlear fluid. The waves in the fluid cause the basilar membrane to move up and down.
The motion of the basilar membrane is dependent on […]
Frequency
What part of the basilar membrane vibrates when the sound is low frequency?
The outermost part relative to the middle ear.
What part of the basilar membrane vibrates when the sound is high frequency?
The innermost part relative to the middle ear.
What part of the basilar membrane vibrates when a complex sound is played?
Many different locations will vibrate at once.
What is done with the motion of the basilar membrane once it vibrates? Where does this occur?
The motion is converted into neuronal activity at the organ of Corti.
Describe the structure of the organ of corti and the key cells in it.
The basilar membrane is at the bottom. Stacked on top of it is various cells, increase outer hair cells and inner hair cells. These hair cells have stereocilia. On top of the hair cells is the tectorial membrane.
Where are ion channels located in the ear?
In the hair cells.
How many rows of each type of hair cells are there in the organ of Corti?
There are 3 rows of outer hair cells and 1 row of inner hair cells.
Explain how the basilar membrane interacts with the hair cells and the effect produced.
As the basilar membrane moves up and down, the stereocilia of the hair cells move and get bent. This produces biomechanical forces with the tectorial membrane. This causes the stereocilia to bend one way or the other depending on how the basilar membrane is moving.
How do the properties of outer hair cells differ from those of inner hair cells
Outer hair cells are capable of moving on their own, and they have electomotility. This allows them to move back and forth in response to sound.
Outer hair cells […] when depolarized and […] when hyperpolarized.
Shorten, lengthen
What is the hypothesized function of hair cell electromotility?
It augments basilar membrane motion.
Give an example of how outer hair cell electromotility can be used clinically.
The otoacoustic emissions, meaning the reflex of the outer hair cells to move, can be used to evaluate hearing in newborns. If a click is produced, this means the auditory system is functioning correctly.
