Physiology of Hearing

Vocabulary terms and definitions covering the anatomy and physiology of the human ear, auditory signal transduction, and cckar mechanics as described in the transcript.

Pinna

Structure of the outer ear that collects sound waves, directs them into the external auditory canal, and helps in localization of sound.

External auditory canal

Part of the outer ear that amplifies sound waves and directs them toward the middle ear.

Ossicles

Three small bones in the middle ear called the malus, enus, and stapes which amplify sound waves and transmit them from the e drum to the inner ear.

Ccka

The main organ of hearing, which is $35\,mm$ long and makes $2\,and\,3/4$ turns, responsible for converting sound waves into neural signals.

Scala vestibuli and Scala tempany

The upper and lower chambers of the ccka, respectively, which contain paraly rich in sodium ion.

Scala media

The Middle cckar chamber which has stria vascularis that secretes endolymph rich in potassium ion.

Endocochlear potential

The electrical state where the Scala media is positive by $85\,molt$ relative to the Scala vestibuli and Scala tempany.

Oval window

A membrane that separates the middle ear from the inner ear through which sound waves enter the ccka.

Bassel membrane

A thin flexible structure running the length of the ccka that contains thousands of tiny hair cells; it is stiffer at the base and more thin and flexible towards the apex.

Tectorial membrane

A gel-like structure that overlies the hair cells in the ccka.

Glutamate

The neurotransmitter released by hair cells when their hair-like projections bend, stimulating auditory nerve fibers.

Cckar amplifier

A specialized system involving outer hair cells that actively contract and expand to amplify the vibrations of the Bassel membrane.

Organ of CTI

The structure that contains the receptors for hearing, including inner and outer hair cells.

Preston

A motor protein found in hair cells.

Stereocilia

Hairlike protrusions on hair cells arranged in a row of progressively decreasing height.

Kinocilia

Specialized single long cilium found at one end of the stereocilia bundle, present in mammals only during early development.

Tip links

Fine elastic structures that connect stereocilia and contain mechanically sensitive cat ion channels for potassium and calcium.

Inner hair cells

A single row of around $3500$ cells responsible for transmitting the majority of sensory input, with $95\%$ of sensory neurons innervating them.

Outer hair cells

Three rows of about $20000$ cells that play a critical role in amplifying sound signals; only $5$ to $10\%$ of sensory neurons innervate them.

Spiral ganglion

Contains the cell bodies of bipolar sensory neurons that form synapses with hair cells to transmit signals to the brain stem.

Traveling wave theory of Von Becki

Theory stating sound waves create a wave along the Bassel membrane that peaks at specific locations: higher frequencies near the base and lower frequencies near the apex.