Unit 2: Anatomy & Physiology

Which of the following statements is false? Circle all that apply.

Cells in the LSO are mostly EE type; Cells in the MSO are mostly IE type

(T/F) Type-I auditory nerve fibers innervate both the outer and inner hair cells

False

Which among the following nuclei in the midbrain?

Inferior Colliculus

Which among the following nuclei is considered a switchboard to the higher auditory centers?

Inferior colliculus, because auditory inputs from the lower centers converge here

Which cortical layer receives afferent inputs from the thalamus?

Layer 4

When a neuron is activated by a hair cell, or by another neuron...

its firing rate increases above its spontaneous rate

Which among the following is not related to frequency coding?

none of these; all relate to coding of frequency

The ridges in the pinna filter incoming sound. Which type of filter best describes its effect on sound?

notch

Which layer of the cortex receives the majority of the information form lower level nuclei?

4

Which of the following statements about the tuning curve is false?

A tuning curve tells us how much gain is provided by the inner hair cell

The tympanic membrane transfers vibrations from _______ to _____________________.

Air, Ossicles

Which of the following are functions of the outer hair cell? (Select all answers that apply.)

Amplification of basilar membrane motion at low sound levels; Compression of basilar membrane motion at high sound levels; Sharpening of the basilar membrane response

Which order describes the flow of neural inputs in the cortex?

Area 41 -> Area 42 -> Area 42 -> Area 44 -> Area 45

The order of afferent information flow in the auditory system is ______________________________________ Abbreviations: A1 - Primary Auditory Cortex CN - Cochlear Nucleus IC - Inferior Colliculus LL - Lateral Lemniscus MGB - Medial Geniculate Body SOC - Superior Olivary Complex

CN -> SOC -> LL -> IC -> MGB -> A1

The pinna aids in localization on the vertical plane when the sound is coming from which of the following directions?

Directly in front of the head

(T/F) Tonotopic organization occurs only in the cochlea.

False

(T/F) In adults, the external ear is always a straight tube

False

Which of the following descriptions of cochlear fluid is false?

Endolymph is located in the Scala Media and is high in K+, low in Na+

(T/F) The stereocilia of the inner hair cells are attached to the tectorial membrane.

False

Match the following landmarks with their locations in the middle ear space:

Eustachian Tube = anterior wall Stapes tendon = posterior wall Round window = medial wall Jugular bulb = Floor

When you are in the an airplane and your ears "pop", which part of the middle ear is involved in this "pop"?

Eustachian tube

The peripheral auditory system consists of (select all that apply):

External Ear, Inner Ear, Middle Ear

(T/F) The cochlear traveling wave is the same as a sound wave

False: the traveling wave is more like a water wave (surface wave)

(T/F) The cochlear traveling wave is the same as a sound wave.

False: the traveling wave is more like a water wave (surface wave)

(T/F) Deflection of stereocilia in the inner hair cell towards the modiolus leads to auditory nerve firing.

False; Stereocilia deflection away from the modiolus leads to auditory nerve firing

(T/F) Tonotopy that starts in the cochlea is maintained throughout the auditory system, except the cortex.

False; tonotopy is preserved throughout the auditory system, including the cortex.

The large dynamic range in the auditory system is encoded by the auditory nerve using ______________________________________

Fibers that have different spontaneous rates, thresholds, and saturation levels

Which of the following processes is performed by the Pinna? (Select all that apply.)

Filtering, Funneling

Frequency tuning in the auditory nerve means that the auditory nerve is:

Frequency specific

The most basal end of the basilar membrane is responsive to ______ frequencies.

High

The cortex is the center of multimodal processing. Name two other auditory nuclei which also receive multimodal information.

IC; MGB

Name the two functions of the middle ear and explain how the middle achieves this.

Impendence matching; protection

Match the following:

Inner hair cell = Type-I afferent nerve fiber Outer hair cell = Efferent nerve fiber and Type-II afferent nerve fiber Convergence = Type-I afferent nerve fiber Divergence = Type-II afferent nerve fiber

Convergence is a property of __________________________________ and divergence is a property of ______________________________________________.

Inner hair cells and type-I auditory fibers; Outer hair cells and type-II auditory fibers

Match the following terms with their meaning:

Ipsilateral = same side as the stimulus or measurement Contralateral = side opposite to the stimulus or measurement Monaural = inputs/processing information from only one ear Binaural = inputs/processing information from both ears

The middle ear is important because:

It matches the impedance of the air in the ear canal with the fluid in the cochlea

Match the auditory nerve fiber type with its properties

Low threshold = high spontaneous rate fibers High threshold = low spontaneous rate fibers Small dynamic range = high spontaneous rate fibers Large dynamic range = low spontaneous rate fibers

An input sound is played to the ear, causing both the inner and outer hair cells to respond. The sound remains constant, but at some point the activity of the outer hair cells is reduced. Which among the following mechanisms may be responsible for this reduction?

Medial olivocochlear system

Which among the following is not related to frequency coding?

None of these: all relate to coding of frequency

The ossicles are connected to the cochlea via the __________________.

Oval window

Which of the following are examples of frequency coding? Select all that apply.

Place theory; Volley theory

When the stereocilia move, causing ion channels to open, ______________________ is the ion that flows into the cell

Potassium K+

Match the each following Brodmann areas with its name.

Primary auditory cortex = 41 Secondary auditory cortex = 42 Auditory association cortex = 22 Broca's area= 44 & 45

The traveling wave occurs because of the pressure differential between:

Scala vestibuli and Scala tympani

Which of the following parts of the inner ear does not take part in hearing?

Semicircular canals

The cochlea is where __________________ occurs. (Select all that apply.)

Separation of frequency components, Transduction

What is tonotopic organization?

Spatial arrangement of the basilar membrane based on which frequencies achieve maximal traveling wave amplitude

Match the following with their function/projection:

Spherical bushy cell = sends axons to both lateral and medial superior olive Octopus cell = coincidence detector Fusiform cells = spectral notch detector Globular bushy cell = sends axons to the contralateral medial nucleus of the trapezoid body

Which of the following nuclei is responsible for binaural integration?

Superior Olivary Complex

Which of the following is true about the resting potentials of the inner and outer hair cells? Circle all that apply.

The resting potential for inner hair cells is -45 mV; The resting potential for outer hair cells is -70 mV

Which of the following describe differences between the stereocilia of the inner hair cells (IHCs) and outer hair cells (OHCs)? Select all answers that apply.

The stereocilia of the IHCs are not embedded in the tectorial membrane, whereas the stereocilia of the OHCs are; The stereocilia of the OHCs are arranged in a V or W shape, whereas the stereocilia of the IHCs are arranged in a straight or slightly-curved line

Which among the following statements is true about the IHCs and OHCs?

There are more OHCs than IHCs

Which among the following statements about action potentials is false?

They cannot be generated by neurons in the absence of external stimulation

What is the primary function of the efferent fibers that project from the medial olivary nucleus to the cochlea? How do they achieve this?

They inhibit the cochlear active process, decreasing OHC amplification

Match the three chambers of the cochlea with their order from top to bottom.

Top: Scala Vestibuli Middle: Scala media Bottom: Scala tympani

(T/F) A tuning curve for an AN fiber tells us the characteristic frequency and the bandwidth of the fiber

True

(T/F) The action potential is an all-or-none phenomenon

True

(T/F) The medial superior olive (MSO) is responsible for processing interaural time differences (ITD).

True

(T/F) The pinna helps us in localizing sounds when the sound source is in the median plane.

True

The thumbtack analogy works for the sounds boosted by the middle ear because the ______________________ is bigger than the ____________________

Tympanic membrane, Oval window

The amplification and compression in the cochlea leads to:

a large dynamic range of hearing

The activity of the medial olivocochlear neurons (MOC) causes ________________ in the cochlea.

a reduction in outer hair cell amplification

What is the epithelial migration in the ear canal useful for?

cleaning debris/repairing tympanic membrane perforations

There are two types of neural connections to the hair cells. The _______________ fibers carry information from the hair cell to the brain and the _____________ fibers bring information from the brain back to the hair cell

afferent; efferent

The middle ear matches the impedance (loosely, resistance to the flow of energy) between ______________________ and ____________________

air in the ear canal; fluid in the cochlea

There are two labyrinths which house our auditory system. The hard shell is called the __________ labyrinth and the softer inside is called the ________________ labyrinth.

bony; membranous

Which among the following cells are involved in coding interaural time differences?

cells in the medial superior olive

Where does diversification and parallel processing in the auditory system start?

cochlear nucleus

You take part in an experiment where you are blindfolded and sounds are played to you through speakers. You are asked to indicate which of 5 locations the sound is coming from; directly in front of you, 90 degree to your left, 90 degrees to your right, directly behind you, or directly above you. Which part(s) of your auditory system would be most helpful for localizing the sound if it is coming from...

directly in front of you = fusiform cells in the CN 90 degrees to your left = cells in both the MSO and LSO 90 degrees to your right = cells in both the MSO and LSO directly behind you = fusiform cells in the CN directly above you = fusiform cells in the CN

The large dynamic range in the auditory system is encoded by the auditory nerve using __________________________________

fibers that have different spontaneous rates, thresholds, and saturation levels

What moves the stereocilia of the inner hair cells?

fluid displacement

The malleolar-incudal joint is formed by the:

head of the malleus and body of incus

In the image on the right, the ____________ frequencies are carried by the blue auditory nerve fiber, and the __________ frequencies are carried by the yellow auditory nerve fiber

high; low

The traveling wave starts with _______ velocity, ____________ close to the characteristic frequency place, and has its _____________ amplitude close to the characteristic frequency place

high; slows down; highest

What does the transfer function illustrate?

how a system changes the sound that passes through it. For each frequency, it plots the change (gain) from input to output

How does the acoustic reflex change sound transduction through the middle ear?

it attenuates low frequencies

In 1-2 sentences, describe the structure and role of the modiolus

it is the bony stem around the cochlea coils. The bone in the modiolus is porous, allows Auditory Nerve fibers to pass through it

Rate coding helps the auditory nerve encode _____________ information for the brain.

level

The rate of auditory nerve fibers encodes _________ information for the brain.

level

Which of the bones of the ossicular chain act in a lever action, and how are they able to achieve this feat?

malleus; incus

The Jeffress model of coincidence detection for interaural time differences (ITDs) works for birds, but not so well for mammals because:

mammals do not appear to have a spatial representation of time difference in the brain

Someone shrunk you down to the size of a grain of rice and dropped you into the tympanic cavity. You see a stirrup-shaped bone attached to the wall that you facing. You also see a translucent membrane lower down, and in between the bone and this translucent window, you see a big bulge. You realize you are staring at the ____________ wall of the middle ear, and that the translucent membrane is the _________________.

medial; round window

As you move from base to apex, the cochlea gets _______________, and the basilar membrane gets _____________ and _____________.

narrower; wider; looser

Type II auditory nerve fibers innervate which of the following organ of Corti structures?

outer hair cells

The pushing of the stapes into the oval window causes the _________________ to be pushed out.

round window

When the stapes pushes into the oval window, which membrane pushes out?

round window

Which of the following parts of the inner ear does not take part in hearing?

semicircular canals

Which structure in the organ of Corti is considered part of the auditory nerve?

spiral ganglion cells

Which of the following is responsible for supplying nutrients to the organ of Corti?

stria vascularis

The peripheral auditory system is in the ____________ bone

temporal

What does "threshold" mean with respect to the auditory nerve?

the minimum sound level required to raise the firing rate of the auditory nerve above its spontaneous firing rate

The place on the basilar membrane where the characteristic frequency = 1 kHz is:

the place where the movement is maximal when you put in a 1 kHz tone

The fact that perilymph and endolymph have different concentrations of K+ and Na+ ions means:

they enable hair cell depolarization (the endolymph is rich in K+ which flows into hair cells when their ion channels are open, depolarizing them)

Phase locking in the auditory nerve helps code ___________ & __________.

timing; frequency

Deflection of the stereocilia away from the modiolus causes:

tip links to open, leading to depolarization of the inner or outer hair cell