Physiology - Cochlear Division

What are the functions of CN VIII?

Detect amplitude, intensity, direction and laterality, frequency components (pitch), temproal components.

Hair cells are what type of receptor?

Mechanoreceptors

The air-filled portion of the ear that receives sound from the external environment and funnels it to the tympanic membrane, causing it to vibrate.

Outer Ear

External, Middle, or Inner Ear? Pinna

External

External, Middle, or Inner Ear? Auricle

External

External, Middle, or Inner Ear? External Auditory Meatus

External

External, Middle, or Inner Ear?Malleus

Middle

External, Middle, or Inner Ear? Incus

Middle

External, Middle, or Inner Ear? Stapes

Middle

External, Middle, or Inner Ear? Semicircular canals

Inner

External, Middle, or Inner Ear? Cochlea

Inner

External, Middle, or Inner Ear? Tragus

External

External, Middle, or Inner Ear? Concha

External

External, Middle, or Inner Ear? Vestibule

Inner

External, Middle, or Inner Ear? Utricle

Inner

External, Middle, or Inner Ear? Saccule

Inner

External, Middle, or Inner Ear? Tympanic Membrane

Middle

External, Middle, or Inner Ear? Oval Window

Middle

The portion of the ear that extends from the tympanic membrane to the external aspect of the oval window.

Middle Ear

This section of the ear functions to transfer sound energy into mechanical energy.

Middle Ear

The middle ear transfers sound energy into mechanical energy via what?

Ossicles

What are the three ossicles?

Malleus, Incus, Stapes

What is the smallest bone in the body?

Stapes

What is the "hammer"?

Malleus

What is the "anvil"?

Incus

What is the "Stirrup"?

Stapes

What is attached to the tympanic membrane and moves when the eardrum vibrates?

Malleus

What muscle is attached to the malleus?

Tensor tympani muscle

What CN innervates the malleus?

CN V

Malleus is attached to what?

Tympanic membrane

What is the middle ossicle?

Incus

What connects the hammer to the stirrup?

Incus

What is in the oval window?

Stapes

What muscle is attached to the stapes?

Stapedius

Stapedius muscle is innervated by what CN?

CN VII

Transforming pressure waves into mechanical vibrations is the goal of what?

Ossicles

The internal surface of the oval window leads to a fluid filled area that contains the sensory receptors for the detection of sound.

Inner ear

The inner ear lies in what bone?

Temporal

The section of the temporal bone in which the inner ear lies is called what?

Bony labyrinth

The passages of the inner ear are lined with a membranous labyrinth that forms a series of sacs and ducts and are suspended within the bony labyrinth by what?

Perilymph

The interior of the membranous labyrinth is filled with what?

Endolymph

What is the small oval chamber that connects the oval window with the cochlea and the semicircular canals?

Vesitbule

The utricle and saccule are sections of what structure?

Vestibule

Both the utricle and saccule have specialized sensory epithelium called what?

maculae

Maculae are innervated by what CN?

CN VIII (vestibular division)

What are the 3 canals within the bony labyrinth that communicate with the vestibule?

Semicircular canals

The semicircular canals occupy how many planes in space?

3

What is the shell shaped part of the bony labyrinth that communicates with the vestibule?

Cochlea

Where is the Organ of Corti located?

Cochlea

In order to have sound detection, there must be movement of fluid in what?

Cochlea

The membranous cochlea is called the what?

Cochlear duct

The membranous cochlea is called the cochlear duct and is firmly anchored to what?

Cochlear canal

The membranous cochlea is called the cochlear duct and is firmly anchored to the cochlear canal by what?

Series of ligaments and memrbanes

The membranous cochlea is called the cochlear duct and is firmly anchored to the cochlear canal, which gives it what shape?

Triangular

What is located above the cochlear duct and is directly continuous with the perilymph of the vestibule.

Scala Vestibuli

The scala vestibuli is separated from the cochlear duct by what?

Reissner's membrane

What is located below the cochlear duct and ends blindly at the round window?

Scala tympani

What contains perilymph and is separated from the cochlear duct by the basilar membrane?

Scala tympani

What is continuous with scala vestibuli at the apex?

Scala tympani

The scala vestibuli and scala tympani are continuous through an opening called what?

Helicotrema

The cochlear duct is filled with what?

Endolymph

What are the 3 walls of the scala media?

Spiral ligament, Reissner's membrane, Basilar membrane

What adheres the duct to the bony surface and contains secretory epithelium that produces the endolymph?

Spiral Ligament

What forms the roof of the cochlear duct?

Reissner's membrane

What forms the floor of the cochlear duct?

Basilar membrane

The Organ of Corti rests on what structure?

Basilar membrane

The hair cells are inserted on their _______________ ends into the overlying gelatinous tectorial membrane.

Apical

The hair cells are inserted on their apical ends into the overlying gelatinous _____________________________________.

Tectorial membrane

Vibrations of the basilar membrane are caused by movement of what?

Perilymph

Vibrations of the basilar membrane move what?

Hair cells

When hair cells shift toward the _________________________, it activates mechanosensitive transduction channels in the hair cell membrane.

Tallest steriocilia

When hair cells shift toward the tallest stereocilia, it activates ______________________________________channels in the hair cell membrane.

mechanosensitive transduction

The opening of the mechanosensitive transduction channels do what to the hair cells?

Depolarize

The narrow portion of the basilar membrane is called the base. It is located near what structure?

Stapes

Which part of the basilar membrane is compliant?

Apex

Which part of the basilar membrane is stiff?

Base

Which part of the basilar membrane is responsible for higher frequencies?

Base

Which part of the basilar membrane is responsible for lower frequencies?

Apex

Why do people lose the ability to hear higher frequencies with presbycusis?

The base of the basilar membrane is stiff and narrow. As we age, it will harden, causing loss of sound of higher frequencies.

Primary neurons of the auditory portion of CN VIII are located in what?

Spiral ganglia

2nd order neurons from the dorsal and ventral cochlear nuclei project _________________.

Bilaterally

2nd order neurons: from the dorsal and ventral cochlear nuclei ascend in the ___________________________.

Lateral lemniscus

3rd order neurons: cell bodies are located where?

Inferior Colliculus

Fibers from the ventral cochlear nucleus project to bilateral ______________________.

Superior olives

What is the function of the superior olives?

Sound localization

The ICs are connected via what?

Commissural fibers

Cells from IC project axons bilaterally via _________________ of the IC to terminate in the medial geniculate nucleus of the thalamus.

Brachium

Cells from IC project axons ____________________ via brachium of the IC to terminate in the medial geniculate nucleus of the thalamus.

Bilaterally

Cells from IC project axons bilaterally via brachium of the IC to terminate in the _________________________ of the thalamus.

Medial geniculate nucleus

The medial geniculate nucleus is located where?

Thalamus

Medial geniculate cells project ipsilaterally to where?

Primary auditory cortex

If there is a lesion on the cochlear nerve or nuclei, what deficit will arise?

Unilateral deafness

If there is a lesion central to the cochlear nuclei, what deficit will arise?

Either no deficit, mild/partial bilateral deafness, or trouble with sound localization

What type of deafness can be described as sound transmissions blocked from reaching inner ear?

Conductive

What type of deafness cause is damage to sensory receptors, nerve, or nuclei?

Sensorineural

What tests help us differentiate between the two types of deafness?

Weber, Rinne