Hearing
What sound wave characteristic determines the volume of the sound
amplitude
lesions central to the cochlear nucleus cause
bilateral hearing loss
The ability of the ear to discriminate sound intensities over an extremely wide range is called _________. a. Vestibulo-ocular reflex b. The "Place" Principle c.The Power Law d. Impedance Matching
c. The Power Law
If a person has selective hearing loss to particular frequencies of sound waves, what is most likely affected?
cochlea and cochlear nerve
Where do 2nd order neurons terminate
cross over in trapezoid body of medulla
What structure converts sound waves to vibrational frequencies for hearing? a. Semicircular ducts b. Utricle c. Rhodopsin d. Tympanic membrane
d. Tympanic membrane
A majority of fibers for the auditory pathway decussate (cross over) in the _______ a. Auditory cortex b. Pons c. Midbrain d. Thalamus e. Medulla
e. Medulla
What do the top of the hair cells sit in
endolymph
What is the difference between endolymph and perilymph
endolymph= high K+ and low Na+2 perilymph= high Na+2 and low K+
symptoms of conductive hearing loss
equal hearing loss in ALL frequencies well preserved speech discrimmination hear speech in noisy background better than in quiet background speak louder and loud speech is heard
What are the 3 components of the ear
external ear, middle ear, inner ear
Where along the basilar membrane will higher frequency sounds stimulate an action potential? Where are lower frequency sounds "heard"
higher frequency= near base lower frequency= near apex
What structures are affected with sensorineural hearing loss
inner ear basilar membrane/cochlea
Where are intermediate frequencies activating the membrane
intermediate distances between the 2 extremes
causes of conductive hearing loss
lesions of external or middle ear impacted cerumen in external canal chronic otitis
which frequencies are mostly affected by attenuation
low frequency
At what volume can low and high frequencies be detected
low=high volume high= low volume
What is the order of the ossicles from external to internal
malleus, incus, stapes
What is a decibel? How does this relate to the "power law"
measurement of loudness power law= ear can discriminate differences in sound intensity ears can barely detect 1 decibel as a change in sound, can tell difference at greater change
Where are low frequency sounds cause activation of the basilar membrane?
near the apex of the cochlea
Where do higher frequency sounds cause activation of the basilar membrane?
near the base of the cochlea
Is endolymph or perilymph more like CSF
perilymph
what do the base of the hair cells sits in
perilymph
what 2 environments will utilize attenuation of sound
protect the cochlea from damaging vibrations and masks low frequency sounds in loud environments
what is "impedance matching"
reduces the distance between the ossicles but increases the force of movement vibration on tympanic membrane is proportional to vibration on stapes
Which tube has endolymph
scala media
Which inner tubes of the cochlea are filled with perilymph?
scala vestibuli and scala tympani
The cochlea: What are the 3 inner tubes of the cochlea?
scala vestibuli, scala media, scala tympani
amplification to the speech specifically goes with
sensorineural hearing loss
symptoms of sensorineural hearing loss
some frequencies (typically low) heard better difficulty hearing speech, especially when mixed with background noise annoyed by loud speech
What 3 characteristics of sounds are detected in the cerebral cortex
sound frequency (pitch) discrimination of sound patterns (speech) determination of direction from which sound came
what 2 muscles are involved in attenuation of sound
stapedius muscle and tensor tympani
Where is the organ of Corti?
surface of membrane in cochlea
How does change in perilymph pressure travel through the cochlea
through the hair cells
peripheral lesions to the cochlear nucleus cause
unilateral hearing loss
What membranes separate each tube of the cochlea?
vestibular membrane (reissner's membrane) separates vestibuli and media basilar membrane separates tympani and media
Is it common to have vestibular symptoms, such as vertigo, with hearing loss
yes
What other pathways will auditory information travel? What purposes are these alternate pathways
-some will traveling to Reticular activating system to respond to loud sounds to wake up; sympathetic NS response -go to vermis of cerebellum=sympathetic NS in response to loud sound
what is the frequency for understanding speech
500-4000Hz
What type of nerves are cochlear nerve? Where do the cell bodies reside?
Bipolar (some references say Pseudounipolar because of the long central processes) and reside in Spiral Ganglion
What type of deafness occurs with absence or disorders of the ossicles? How is it usually managed?
Conduction deafness. Amplification of all frequencies
Unilateral (uniaural, or monoaural) hearing loss indicates the lesion is _______.
Distal to the cochlear nucleus
Which is FALSE concerning attenuation of sound? Masks low frequency sounds in loud environments Slight contraction of the tensor tympani muscle pulls handle of Malleus in Contraction of the stapedius muscle pulls stapes off the oval window Rapidly reduces higher frequency vibrations by 30-40 decibels Protects the cochlear hair cells from damaging vibrations
Protects the cochlear hair cells from damaging vibrations
From the hair cells of the organ of Corti, where do neural impulses travel? Which hair cells stimulate nerve impulses
They go to the spiral ganglion of Corti, which sends axons to the cochlear nerve; inner and outer hair cells
Where do 1 st order nerve fibers from the spiral ganglion synapse?
In the brainstem, cochlear nuclei
What is the organ of corti function
sensory receptor for hearing
How does the brain determine the direction of sound
the time lag between the entry of sound into one ear and its entry into the opposite ear detected in the medial superior olivary nucleus difference between the intensities of sounds in the 2 ears detected by the lateral SON
What are the structures sound waves pass through as they travel to the inner ear
cochlea and semicircular canals, saccule, and utricle
What are the 3 main categories of hearing loss
conductive, central hearing disorders, sensorineural hearing loss
causes of sensorineural hearing loss
congenital/hereditary cochlear damage ototoxic drugs Meniere's disease presbycusis noise induced acoustic neuroma
What is resonant frequency?
the natural frequency of an object
What characteristic of sound is detected by the place principle?
frequency
What sound wave characteristic determines the pitch or tone of the sound
frequency
How is intensity of sound (loudness) detected and relayed
hair cells excite the nerve endings at a more rapid rate= temporal summation hair cells on fringes are stimulated= spatial summation outer layer of hair cells only stimulated when vibration is high, signaling "very loud" to the CNS
How does endolymph differ from perilymph? (Which is TRUE) Endolymph is more electronegative than perilymph due to lower K+ Endolymph fills the scala vestibule and scala tympani Endolymph resembles cerebrospinal fluid The top of the hair cells of the cochlea are in perilymph The -150mV intracellular potential in the hair cell makes it more sensitive to sound vibrations
The -150mV intracellular potential in the hair cell makes it more sensitive to sound vibrations
Contraction of the stapedius and tensor tympani muscles to protect the cochlea from damaging vibrations is _____ Question options: The "Place" Principle The Attenuation Reflex Vestibulo-ocular reflex Impedance Matching
The Attenuation Reflex
What does the stapes contact
oval window
What mechanisms help the brain determine the direction from which a sound comes from? (choose all that apply) Question options: Stimulation of outer layer of hair cells. Hair cells excited at more rapid rate, causing temporal summation. The amplitude of the vibration of the basilar membrane. Hair cells on the fringes of the frequency range stimulated, causing spatial summation. High frequency causes maximal activation of basilar membrane near the apex of the cochlea. The difference between the sound intensities in the 2 ears with the closer ear hearing a noise louder. Time lag between entry of sound into one ear and its entry into the other ear. High frequency sounds activate the basilar membrane near the base of the cochlea.
-The difference between the sound intensities in the 2 ears with the closer ear hearing a noise louder. -Time lag between entry of sound into one ear and its entry into the other ear.
Place in order the sequence of nerve depolarization of the auditory pathway. ___Auditory cortex of the temporal lobe _Dorsal or Ventral cochlear nuclei of the medulla __Medial Geniculate nucleus _Spiral ganglia_ _Superior Olivary nucleus __Inferior colliculus
1. Spiral ganglia 2. dorsal or ventral cochlear nuclei of medulla 3. superior olivary nucleus 4. inferior colliculus 5. medial geniculate 6. auditory cortex of temporal lobe
Place in order the structures that sound waves pass through as vibrations to stimulate the cochlear nerve. __Malleus __Stapes __Oval window __Incus __Membranous labyrinth of cochlea __Tympanic membrane
1. tympanic membrane 2. malleus 3. incus 4. stapes 5. oval window 6. membranous labyrinth of cochlea
What mechanisms help the brain determine the loudness or volume of the sound entering the ear? (choose all that apply) 1.Hair cells excited at more rapid rate, causing temporal summation. 2.Hair cells on the fringes of the frequency range stimulated, causing spatial summation. 3.The difference between the sound intensities in the 2 ears with the closer ear hearing a noise louder. 4.Stimulation of outer layer of hair cells. 5.The amplitude of the vibration of the basilar membrane. 6.Time lag between entry of sound into one ear and its entry into the other ear. 7. Low frequency sounds cause maximal activation of basilar membrane near the apex of the cochlea. 8. High frequency sounds activate the basilar membrane near the base of the cochlea.
1.Hair cells excited at more rapid rate, causing temporal summation. 2.Hair cells on the fringes of the frequency range stimulated, causing spatial summation. 4.Stimulation of outer layer of hair cells= only when vibration is high
What is the central auditory pathway
1.receptor cell body in spiral ganglion, synapses in brainstem (medulla) in cochlear nerve 2. cell bodies in cochlear nuclei of medulla, decussate and synapse in SON of Pons (superior olivary nucleus of Pons) on same side 3. cell bodies in SON of Pons terminate in midbrain (inferior colliculi) 4. cell bodies in inferior colliculi terminate in thalamus 5. medial geniculate nucleus of thalamus to cerebral cortex (temporal lobe)
Match the type of deafness with its cause(s). __Chronic exposure to loud sounds damages basilar fibers near the apex. __Sensitivity to certain antibiotics damages the Organ of Corti __Old age damages basilar fibers at the base of the cochlea. __Chronic ear infections and otosclerosis scar the ossicles, preventing transmission of vibration 1.High frequency nerve deafness 2.Low frequency nerve deafness 3.All frequency nerve deafness 4.Conduction deafness
2,3,1,4
Match the structure to its description or function. __Communicates with the round window, inferior to the basilar membrane. __Separates the scala tympani from the scala media and contains the organ of corti __Separates the scala media from the scala vestibuli __Bending of hair cells toward this perilymph filled structure causes depolarization __Contains the stria vascularis, which makes endolymph 1. Scala vestibuli 2. Scala media 3. Scala tympani 4. Vestibular Membrane (Reissner's) 5. Basilar membrane
3,5,4,1,2
Match the cell or structure to its description or function. __Contains the gel coating in which the ends of the hair cells are embedded. __About 12,000. Stimulated only when vibration is high, signaling "very loud" to the CNS. __Project upward from hair cells to gel coating, bend toward or away from scala vestibule. __About 3500. Stimulated first, main cell responsible for conducting receptor potential to cochlear nerve endings. __Anchors the basilar fiber to the basilar membrane as it vibrates. 1. Outer hair cells 2. Inner hair cells 3. Stereocilia 4. Tectorial membrane 5. Modiolus
4,1,3,2,5
Reducing the distance between the ossicles but increasing the force of movement is called _______ Question options: The "Place" Principle Attenuation of sound Impedance Matching Vestibulo-ocular reflex
Impedance Matching
What is the place principle?
Nervous system detects sound frequencies by determining positions along basilar membrane that are most stimulated activate specific neurons in response to specific frequencies
What is the receptor for hearing? Question options: Macula of the utricle Rods and Cones Crista ampullaris Organ of Corti
Organ of Corti
Which is FALSE concerning the basilar membrane of the cochlea? a.The basilar membrane separates the scala vestibuli from the scala media b.The basilar membrane contains 20,000-30,000 fibers projecting from the modiolus c.The fibers of the basilar membrane at the base are shorter d.The fibers of the basilar membrane at the base are stiffer e. The Organ of Corti lies on the surface of the basilar membrane
a. The basilar membrane separates the scala vestibuli from the scala media
What happens to the lengths and widths of the basilar fibers as they get farther from the base and closer to the apex? How does this affect the pitch of the sound
lengths of fibers increase from base to apex and decrease in diameter this would lower the frequency
what structures are affected with conductive hearing loss
outer and middle ear trouble getting sound in
How is sound frequency registered in the auditory cortex
there are 6 tonotopic maps in auditory cortex high frequency sounds excite neurons at one end of map, low frequency= excite neurons at opposite ends
How does the difference of endolymph and perilymph contribute to the sensitization of the hair cell?
there's a 80+ millivolts difference between endolymph and perilymph. -150 millivolt intracellular potential in hair cell at top and -70 millivolt potential in hair cell at base This allows the hair cells to be extra sensitized and able to respond to the slightest sound
How is spatial orientation of sound preserved through the auditory pathway?
through 3 spatial patterns for termination of different frequencies to in cochlear nuclei, 2 patterns in inferior colliculi, 1 precise pattern for discrete sound frequencies in auditory cortex
