CNS audotiry Flashcards
What does the amplitude of a sound wave correspond to?
Its loudness.
What is sound?
Pressure waves moving past your head.
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: the frequency of the sound waves (pitch) depending of 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 by the cochlea in the inner ear
What is the oval window?
The oval window is a membrane-covered opening in the cochlea of the inner ear that receives vibrations from the stapes, the final ossicle in the middle ear. These vibrations create fluid waves in the cochlea, allowing sound to be converted into electrical signals sent to the brain.
Describe the trajectory of sound up to its arrival in the inner ear.
- Sound waves enter the ear canal and reach the tympanic membrane and causes it to vibrate
- These vibration pass through the ossicles
- The stapes presses agains the oval window, sending the sound waves into the inner ear
What are the three bones in the middle ear and what is their function?
Malleus, incus and stapes. They do amplification of the sound
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 muscles contract to reduce movement of the ossicle and so minimizing the amplification
Where is the round window located and what is its function?
It is just below the oval window
Its main function is to act as a pressure release valve: it moves outward in response to the inward movement of the oval window
Explain how sound energy travels once it has gotten into the inner ear.
When the sound waves have crossed the oval window, the vibrations spread through the cochlear fluid. The fluid waves travel along the cochlear and causes the basilar membrane to vibrate in different areas due to it’s mechanical properties
The motion of the basilar membrane is dependent on […]
the frequency of the sound
What part of the basilar membrane vibrates when the sound is low frequency?
The end
What part of the basilar membrane vibrates when the sound is high frequency?
The beginning
What part of the basilar membrane vibrates when a complex sound is played?
Multiple parts, depending on the frequency break down
Where are the utricle and saccule located and what is their function?
They are in the vestibule of the inner ear. They are part of the vestibular system and are responsible for detecting linear accelerations (such as moving forward or upward) and head position relative to gravity
Describe the structure of the organ of corti and the key cells in it.
It’s in the cochlear duct and on the basilar membrane. In it, there are hair cells with stereocilia that are embedded in the tectorial membrane
Where are ion channels located in the ear?
in the tips of the stereocilia
How many rows of each type of hair cells are there in the organ of Corti?
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.
When the basilar membrane moves, the cells follow that movement, but the stereocilia in the tectorial membrane (gelly) move the other way. The difference in movement causes the channels to open or close
How do the properties of outer hair cells differ from those of inner hair cells
The outer hair cells are electromobile. They receive input from the brain to enhance certain frequencies over others
Outer hair cells […] when depolarized and […] when hyperpolarized.
shorten
lengthened
What is the hypothesized function of hair cell electromotility?
they augment basial membrane motion
Hair cells contain what kind of receptors?
mecano receptors
How does the transduction process occur in hair cells?
When the k+ channels are open at the surface of the stereocilia, the hair cells releases neurotransmitters to the afferent neuron
Mechanotransduction at the […] activates […]
hair cells
afferent neurons
Explain how the tip links activate afferent neurons.
Each stereocilia’s Mecano receptor is connected to the one below, so when they are pulled apart, the receptors open and depolarize the hair cell
What direction of stereocilia movement opens the ion channels?
Pulled apart/ towards the taller ones
K+ causes [hyperpolarization/depolarization] of the membrane of hair cells, because […]
depolarization
it’s bringing more positive ions inside
What is tinnitus?
ringing in the ears
What are the two types of tinnitus?
Transient and chronic
Explain how auditory information travels from the afferents to its final destination.
The 8th cranial nerve brings the information to the medulla, where ipsilateral and contralateral neurons are activated to reach the primary auditory cortex
What is the purpose of the auditory pathways being bilateral?
Bilateral representation comes with a delay in reaching each hemisphere of the primary auditory cortex. It helps localize the sound better
Describe how cochlear implants work.
Electrode are placed to stimulate the basilar membrane in an approximate way
What are the major vestibular organs?
The semicircular canals, the utricle and the saccule
What is the function of each of the vestibular organs?
The 3 semicircular canals detect angular acceleration in the three planes (all about 90° from each other)
The urticle detects horizontal acceleration
The saccule detects vertical acceleration
What is the vestibular ocular reflex?
Even if the head is moving, the eyes can compensate and keep the gaze steady
How does transduction occur in the vestibular organs?
The same stereocilia are present in the semicircular canals. This time, they are in the cupula
Describe the organization of the semicircular canals.
The semicircular canals have an ampulla which is an enlargement in which we can find the hair cells and the stereocilia in the cupula
Describe how the semicircular canals respond to movement.
The fluid in the semicircular canals is in some inertia meaning that the movement of the head will also cause the opening or closing of the ion channels
Describe how the utricle and saccule adapt to motion.
The otoliths are floating above the stereocilia and will move them because of inertia
What causes dizziness and motion sickness
Dizziness: once the rotation is done for a long time, the fluid wants to keep moving after stopping. This will give a perception of spinning
Motion sickness: there is a conflict between the vestibular and the visual information being sent
