Hell

Question 1

(Inner Ear)

1. What does the inner ear consist of?
2. What is cochlea a component of and contains what?
3. The cochlear duct is a component of what and what does it contain?

Answer 1

1. the cochlea and vestibular apparatus
2. component of osseous labyrinth that contains perilymph and cochlear duct
3. Component of membranous labyrtinth and contains endolymph

Question 2

1. The cochlear duct separates two perilymph chambers, what are their names (and which membrane does each contact)?

Answer 2

1. scala vestibuli (contacts the oval window membrane); scala tympani (contacts the round window membrane)

Question 3

1. The cochlear duct (scala media) is ____ in cross section. What separates the cochlear duct from scala vestibuli? What does this present?
2. Should the vestibular membrane be ignored in regard to the mechanicis of hearing?

Answer 3

1. triangular; vestibular membrane; an ionic barrier between perilymph and endolymph
2. yes

Question 4

1. What two things separate the cochlear duct from the scala tympani?
2. What is the basilar membrane critical in? What does it consist of?
3. Are the fibers shortest and stiffest at the base or the apex?

Answer 4

1. an osseous spiral lamina and basilar membrane
2. the physiology of hearing; consists of radial fibers that extend outward from the osseous spiral lamina
3. At the base (longest at the apex)

Question 5

(Spiral Organ)

1. Within the cochlear duct, what sits atop the basilar membrane along its entire length from the base to the apex of the cochlea?
2. What does it feature?
3. Each of the thing above has dozens of what on its free surface?
4. What are the hair cells held in place by?
5. Stereo-cilia project above the reticular plate to make contact with what?
6. Answer above arises from what, and what is it?

Answer 5

1. A Spiral organ (organ of Corti)
2. features receptor cells (hair cells) arranged along one inner row and three outer rows
3. stereo-cilia
4. Reticular membrane (plate) anchored to the basilar membrane
5. tectorial membrane
6. Limbus, tissue mass set solidly on the osseous spiral lamina

Question 6

(Cochlear Nerve)

1. Afferent Neurons of the cochlear nerve have _____ cell bodies located in what, and within what?
2. From the spinal ganglion, zxons traverse what? What percenage of the axons synapse on inner hair cells?

Answer 6

1. bipolar; in a spiral ganglion; within the modiolus

2. The osseous spiral lamina; more than 90%

Question 7

(Cochlear Nerve Cont)

1. Centrally, axons leave the spiral ganglion and pass through what to form what?
2. Where do axons synapse in the brain?

Answer 7

1. Pass though venter of the modiolus to form the cochlear division of the vestibular-cochlear nerve
2. in dorsal and ventral cochlear nuclei

Question 8

(Cochlear nerve cont cont)

1. Cochlear nerve also contains inhibitory efferent axons (from where?) that synapse on what?
2. What does brain accomplish with efferent axons (selectively speaking)

Answer 8

1. (from dorsal nucleus of the trapezoid body); synapse on dendritic endings of afferent neurons and on outer hair cells.
2. Selectively tunes ear sensitity (attention) to different ranges of sound pitch

Question 9

(Mechanics of hearing)

1. Pressure waves are transmitted to what and displace what?
2. Hearing begins with pressure waves impacting the ________, causing in to vibrate. The vibration is transmittted from ____ to ____ to ____. The stapes rocks in and out, causing the membrane of the ______ to produce pressure waves within perilymph of teh _______. Pressure is transmitted without loss to endolymph in the _______ (the vestibular membrane offers no resistance to fluid pressure). The pressure wave displaces the _____, transmitting pressure to the _______ and displacing the membrane of the round window.

Answer 9

1. transmitted to cochlea and displace basilar membrane
2. Tympanic membrane; malleus; incus; stapes; oval window; scala vestibuli; cochlear duct; basilar membrane; scala tympani

Question 10

(Mechanics of Hearing - part two)

1. Movement of the basilar membrane leads to what in hair cells?
2. Movement of the basilar membrane imparts a rocking action, proportional to degree of ______, to the ________, which rests upon the membrane. Cilia, in contact with the stationary _____ membrane, are displaced relative to the moving hair cells. The tectorial membrane doesn’t rock because it is attached to the ________, which sits on bone
3. Cilia displacement (in one direction) opens what kinds of channels? What does this depolarization of? release of what? depolarization of what? and increased frequency of what?
4. Cilia displacement in other direction results in what?
5. Cilia displacement modulates what? Hair cell excitability modulates what? What maintains the high K+ conc of the endolymph?

Answer 10

1. signal transduction
2. displacement; spiral organ; tectorial; limbus
3. K+; hair cells; glutamate neurotransmitter; dendrites that synapse on hair cells; action potential in cochelar nerve
4. hyperpolarization and decreased frequency of action potentials
5. an on-going K= current from the endolymph through the hair cell to the perilymph; APs in the cochlear nerve; dedicated ion pumping cells in the stria vascularis

Question 11

(Properties of Sound)

1. Pressure Waves of air can be interepreted as what?
2. What are the subjective properties of sound?

Answer 11

1. sound

2. pitch, volume, direction

Question 12

(Wave frequency or pitch)

1. As a pressure wave travels from the base to the apex of the cochlea, displacement to the basilar membrane is greatest where?
2. Which frequencies cause displacement of the base of the cochlea? Which travel to the apex of the cochlea?
3. As the pitch increases, the peak amplitude of basilar membrane displacement _______, from the ___ (longest fibers) towards the ____ (shortest fibers) of the cochlea.

Answer 12

1. where the membrane is resonant to the frequency of the traveling wave
2. High frequency; low frequency
3. Regresses; apex; base

Question 13

1. The location of peak amplitude of basilar membrane displacement corresponds to maximal activity of what?
2. How does the brain decipher pitch?
3. The basilar membrane contains a _____ map, which is maintained by the ___.

Answer 13

1. the corresponding hair cells and cochlear nerve fibers (relative to other hair cells in the spiral organ)
2. By determining which fibers of the cochlear nerve (which hair cells of the spiral organ; what place along the basilar membrane) are maximally active (for > 200 Hz)
3. tonotopic, CNS

Question 14

What is the Place Principle?

Answer 14

Pitch is determined by the place of maximal amplitude displacement along the basilar membrane

Question 15

(Volume - amplitude from the high point to the high point in a pressure wave)

1. For a given pitch, the brain interprets volume as a function of what?
2. Increased volume (amplitude) will result in what in each of the following…
   a) basilar membrane
   b) cilia
   c) receptor cells
   d) cochlear nerve axons

Answer 15

1. of the number of axons firing and the frequency of their action potentials
   a) greater excursion of basilar membrane
   b) greater displacement of cilia
   c) greater depolarization of receptor cells
   d) high frequencies of APs in more cochlear nerve axons

Question 16

(Direction - location of the source of teh sound waves)

1. For sounds of low frequency, the brain uses what to determine which ear is closer to the source of the sound? At high frequencites?

Answer 16

1. the phase difference (time-lag) between inputs to right and left ears ; head acts as a barrier resulting in an intensity difference between the near and far ear (pinna also modify and can be moved)

Question 17

(Auditory Pathway)

1. Cochlear nerves synapse in what?
2. The cochlear nuclei contain what order neuron? Thereafter, the auditory pathway is bilateral and complex because of many synaptic possibilites.
3. Fibers from the cochlear nuclei project to what?

Answer 17

1. Dorsal and ventral cochlear nuclei (typically each fiber synapses in both nuclei)
2. second-order neurons
3. dorsal nucleus of the trapezoid body and caudal colliculus (the trapezoid body contains decussating fibers from the cochlear nuclei)

Question 18

1. What is a tract that carries fibers from the cochlear nuclei and the dorsal nucleus of the trapezoid body to the caudal colliculus?
2. Fibers from the caudal colliculus project to the what via the what?
3. Neurons in the medial geniculate nucleus send their axons through the what to the what (which surrounds what)?

Answer 18

1. the lateral
2. to the medial geniculate nucleus via the brachium of the caudal colliculus
3. through the internal capsule, to cerebral cortex surrounding the sylvian sulcus (primary auditory cortex)

Question 19

What are the six main CNS nuclei in the auditory pathway?

Answer 19

1. cochlear nuclei (dorsal and ventral)
2. dorsal nucleus of the trapezoid body
3. caudal colliculus
4. medial geniculate
5. primary auditory cortex
6. auditory association cortex

Question 20

(Cochlear Nuclei)

1. receive input from what?
2. What order of neuron? how organized? source of what?
3. Do second order neurons exhibit continuous background firing that is changed by excursions?
4. Lesions of cochlear nuclei (or cochlea nerve or a cochlea) produce what? Lesions central to the cochlear nuclei affect one or both ears? why?

Answer 20

1. ipsilateral cochlear nerve
2. second order, tonotopically, all central auditory pathways
3. yes
4. unilateral deafness; both; central pathways are bilateral

Question 21

(Dorsal Nucleus of the trapezoid body)

1. each nucleus receives input from what?
2. The nucleus functions in ______ ie detecting phase and intensity differences between the two ears (different neurons respond to the different time lags between the two ears. Pther neurons respond to different intensity differences between the two ears)
3. The nucleus sends output to cranial nerves __ and ___. for what?
4. The nucleus is the source of what that selectively tune the spiral organ for frequency discrimination?

Answer 21

1. right and left ears (via cochlear nuclei)
2. sound localization
3. V and VII - for reflex contraction of tensor tympani and stapedius muscles to dampen loud sound
4. efferent axons (efferent innervation affects the length of outer hair cells which changes the position of teh tectorial membrane which adjusts the sensitivity of inner hair cells)

Question 22

(Caudal colliculus)

1. Receives input via what?
2. Via tectospinal/tectobulbar tracts, output from the caudal colliculus produces what?

Answer 22

1. via the lateral lemniscus

2. reflex turning of the head, ears and eyes toward a sudden sound stimulus

Question 23

(Medial Geniculate)

1. Receives input via what?
2. What takes place at the medial geniculate level?
3. Geniculate neurons project their axons through what to what?

Answer 23

1. via the brachium of the caudal colliculus
2. imprecise sound conciousness
3. through the internal capsule to the primary auditory cortex (the geniculate body functions for sound like the thalamus functions for tactile sense)

Question 24

(Primary Auditory Cortex)

1. Located around what?
2. necessary for what?
3. Has separate what for detecting pitch and direction? Are pitch and direction relayed to the cortex on the same pathway?

Answer 24

1. around the sylvian sulcus
2. recognizing temporal patterns of sound and direction of pitch change (elements of melody, speech, etc)
3. tonotopic maps ; no, they are separate

Question 25

(Auditory Association Cortex)

1. surrounds what?
2. Required to do what?

Answer 25

1. the primary auditory cortex (from which it receives input)
2. to extract meanings of sound patterns and associate learned significance with a particular sound pattern