inner ear part 2

Modiolus

Central core of the cochlea Where blood and nerve supply enter the cochlea

Stereocilia

Found on top of each hair cell Stimulated in response to fluid wave when the stapes displaces the perilymph at the basal end of the cochlea propagating a wave toward the apex of the cochlea

Endolymph

Found within the scala media, utricle, saccule, and semicircular canals High in potassium and low in sodium content

Perilymph

Found within the scala vestibuli and scala tympani High in sodium and low in potassium very similar in composition to the cerebrospinal fluid that surrounds the spinal cord the brain.

Tectorial Membrane

Gelatinous flap covering the tops of the stereocilia of the outer hair cells Hair cells are held between the basilar and tectorial membranes

Contains auditory nerve endings (The Basilar Membrane)

Inner hair cells have approximately 20 nerves for every single hair cell Outer hair cells have approximately 1 nerve for every 10 hair cells

The Organ of Corti

an organ of the inner ear located within the cochlea which contributes to audition. includes three rows of outer hair cells and one row of inner hair cells. Vibrations caused by sound waves bend the stereocilia on these hair cells via an electromechanical force. The hair cells convert mechanical energy into electrical energy that is transmitted to the central nervous system via the auditory nerve to facilitate audition.

What is the organ of Corti composed of?

both supporting cells and mechanosensory hair cells. The arrangement of mechanosensory cells is comprised of inner and outer hair cells along rows

The scala media is filled with a fluid called _________________________

endolymph

Endolymph

has a significant positive ion (+80 m V) in comparison to the essentially neutral ionic charge of the perilymph.

Inner hair cells

1 row of 3,000 hair cells

Outer hair cells

3-5 parallel rows of 12,000 to 15,000 hair cells

The Basilar Membrane

35 millimeter long and variable width (0.1 millimeter at the base and 0.5 millimeter at the apex)

Tonotopically organic (The Basilar Membrane)

Contains the auditory hair cells in its fibrous layer

Wave always travels from the base to the apex of the cochlea

Low frequency tones have longer wavelengths that create maximum wave displacement at the apical end of the cochlea High frequency tones have shorter wavelengths that create maximum wave displacement at the basal end of the cochlea

Ductus reuniens

Pathway that connects the endolymph in the scala media to the endolymph within the vestibular system

Stria vascularis

Produces endolymph Supplies oxygen and nutrients to the cochlea

Reissner's membrane

Separates the scala media from the scala vestibuli

Spiral Ligament

Supports the scala media

The difference or gradient in ion composition and concentration of endolymph versus perilymph serves as an inner ear battery, supplying power for cochlear functions.

The electrochemical potential difference in the cochlea is critical for powering the ongoing active processes within the cochlea

tip-links

Unified movement of stereocilia is enhanced by tiny connections between cilia strands

The organ of Corti

an organ of the inner ear contained within the scala media of the cochlea. It resides on the basilar membrane, a stiff membrane separating the scala tympani and scala media. The scala media is a cavity within the cochlea that contains endolymph which has a high (150 mM) K+ concentration. The endolymph helps to regulate the electrochemical impulses of the auditory hair cells.

The basilar membrane

separates the scala media from the scala tympani

Reissner's membrane

separates the scala vestibuli from another wedge-shaped portion of the tube, named the scala media

Outer Hair Cells

sharpen the fluid wave

Two membranes separate the cochlea

into three portions, or scala

The scala vestibule

is filled with a fluid called perilymph

The scala tympani

is filled with perilymph

cochlea

is tube-shaped and separated into three sections by thin membranes

stereocilia

is used to describe these structures because the cilia move together in a coordinated fashion when deflected by movement of the basilar membrane.

Oval window

moved by the stapes displacing perilymph creating a fluid wave that causes a cascade of movement within the other cochlear structures

What is the primary function of the organ of Corti?

the transduction of auditory signals. Sound waves enter the ear via the auditory canal and cause vibration of the tympanic membrane. Movement of the tympanic membrane causes subsequent vibrations within the ossicles, the three bones of the middle ear, which transfers the energy to the cochlea through the oval window. As the oval window moves, waves propagate through the perilymph fluid inside the scala tympani and then the scala vestibuli of the cochlea. When fluid moves through these structures, the basilar membrane (located between the scala media and scala tympani) shifts respectively to the tectorial membrane