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Hearing-Physiology PowerPoint Presentation

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Description : Check out this medical PowerPoint presentation titled "Hearing: physiology".

This medical PowerPoint presentation is about hearing, the physiological process by which sound waves are detected and interpreted by the brain. The process of hearing involves the ear, which is responsible for collecting sound waves and transmitting them to the brain for interpretation. The ear is divided into three main parts: the outer ear, middle ear, and inner ear.

The outer ear consists of the pinna (the visible part of the ear) and the ear canal. Sound waves enter the ear canal and cause the eardrum (tympanic membrane) to vibrate.

The middle ear contains three small bones called the ossicles (the malleus, incus, and stapes). These bones amplify and transmit the vibrations from the eardrum to the inner ear.

The inner ear contains the cochlea, which is responsible for converting the vibrations into neural signals that are sent to the brain. The cochlea is filled with fluid and contains thousands of hair cells, which are responsible for detecting different frequencies of sound.

When the hair cells are stimulated by the vibrations, they send electrical signals through the auditory nerve to the brainstem, where they are processed and interpreted as sound. The brain then interprets these signals and allows us to hear and understand speech, music, and other sounds.

Tags : Hearing, sound waves, perception of hearing

Published on : Jun 23, 2023 | Views : 1543 | Downloads : 6

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Slide 1-

Hearing: physiology
Slide 2-

Receptors / physiology Energy transduction First goal of a sensory/perceptual system? Transduce environmental energy into neural energy (or energy that can be interpreted by perceptual system). In hearing, environmental energy = pressure or sound waves.
Slide 3-

Energy Transduction (cont.) Pressure / Sound waves
Slide 4-

Energy Transduction (cont.) Pressure / Sound waves When people create a wave, it looks like this: When air molecules do, it looks like this: (Animations courtesy of Dr. Dan Russell, Kettering University)
Slide 5-

Energy Transduction (cont.) Pressure / Sound waves (cont.) We can create a graph of pressure at different locations in space:
Slide 6-

Energy Transduction (cont.) Pressure / Sound waves (cont.) Amplitude (loudness) Loudness is measured by how much the air molecules are compressed after the sound starts, while frequency (pitch) is measured by how long it takes the wave to finish a complete cycle.
Slide 7-

Energy Transduction (cont.) Pressure / Sound waves (cont.) Humans hear tones with frequencies from 20-20,000 Hz. Highest sensitivity in 2000-5000 range. (Baby cry) Most tones aren't pure tones, like those in previous slides, they're complex tones:
Slide 8-

Anatomy of the ear: outer ear, middle ear, inner ear
Slide 9-

Anatomy of the ear: outer ear, middle ear, inner ear Outer ear pinna: part you see; amplifies sounds around 400 hz; plays a role in sound localization auditory canal: cylindrical tube; conducts vibrations to eardrum; acts like a horn - amplifies sound (esp. around 3000 hz) eardrum (tympanic membrane): pressure waves are converted into mechanical motion
Slide 10-

Anatomy of the ear: outer ear, middle ear, inner ear Middle ear
Slide 11-

Anatomy of the ear: outer ear, middle ear, inner ear Middle ear (cont.) ossicles : malleus (hammer), incus (anvil), stapes (stirrup). conduct vibrations from eardrum to oval window more amplification muscles attached to the ossicles can retract reflexively if loud, low frequency sounds are heard, reducing amplitudes at levels that might cause hearing damage.
Slide 12-

Anatomy of the ear: outer ear, middle ear, inner ear Middle ear (cont.) eustachian tube : ossicles are surrounded by air; important to keep pressure in middle ear the same as pressure outside; otherwise eardrum would stiffen and become less responsive. E. tubes go to throat, open every time we swallow, equalizing pressure. A cold can block tubes, resulting in hearing loss (usually temporary). Infection can be transmitted through E. tubes, esp. in children, causing fluid buildup - eardrum can bulge or even burst.
Slide 13-

Anatomy of the ear: outer ear, middle ear, inner ear Middle ear (cont.) Bones of the middle ear are necessary because of the problem of impedance mismatch. That is, sound doesn't conduct well between air & water - most sound will be reflected back. Middle ear problems (conduction deafness) ear drum punctured ear infection - fluid or solid build up in auditory canal. otosclerosis - stiffens stapes so won't function.
Slide 14-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear
Slide 15-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) semicircular canals : Already discussed - used for determining orientation, not hearing oval window 1/15th area of eardrum; helps increase pressure & deal with impedance mismatch problem. cochlea : snail-shell-like structure; contains auditory receptors that transduce sound into neural signals.
Slide 16-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.)
Slide 17-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) vestibular canal: next to oval window; liquid is set in motion here; vibrates reissner's membrane. tympanic canal: connected to vestibular canal via helicotrema (basically a small hole). Vibrates basilar membrane. cochlear duct: separate canal, contains organ of corti.
Slide 18-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) basilar membrane : When pressure is applied to vestibular & tympanic canals, basilar membrane becomes distorted - creating a traveling wave
Slide 19-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) basilar membrane (cont.) Traveling wave Because of the traveling wave, the basilar membrane vibrates differently depending on tone of sound stimulating it.
Slide 20-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) organ of corti : contains hair cell receptors that rest between basilar membrane & tectorial membrane. hair cells : receptors that cause cell to fire when tips are bent.
Slide 21-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) When basilar membrane is displaced, hair cells are bent by tectorial membrane; when a hair cell is stimulated, its neuron fires.
Slide 22-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) inner ear problems - nerve deafness hair cells damaged or broken - can cause tinnitus, or ringing in the ears, other problems cochlear implants - can essentially replace a cochlea for people who have damage for any number of reasons. The implant breaks sounds into component frequencies & then stimulates auditory nerve, much as cochlea would.
Slide 23-

Anatomy of the ear: outer ear, middle ear, inner ear Inner ear (cont.) Bone conduction: alternate way of transmitting sound to inner ear. sounds produce vibration in skull that stimulates inner ear directly (bypassing middle ear) - usually only low frequencies. ex: chewing on food; dentists drill explains why your voice sounds different on tape.
Slide 24-

Brain and auditory cortex
Slide 25-

Brain and auditory cortex auditory nerve : carries info from ear to cortex. Different auditory neurons are sensitive to different frequency tones; frequency tuning curves:
Slide 26-

Brain and auditory cortex Cochlear nucleus: First stop; transmits half info to same side of brain, and half to opposite side. (allows binaural processing) inferior & superior colliculus : Superior colliculus involved in integration of vision & audition. I.C. Has tonotopic organization, meaning neurons sensitive to similar tones are found near each other. auditory cortex : Still tonotopic, some cells require more complex stimuli (than mere pure tones) to become active; clicks, bursts of noise, etc.
Slide 27-

List of terms, section 3 Transduction Pressure/Sound waves Amplitude (loudness) Compression, rarefaction Frequency (pitch) Wavelength Pure tone, complex tone Pinna Auditory canal Eardrum/tympanic membrane Ossicles Malleus, Incus, Stapes Eustachian tube Impedence mismatch Otosclerosis Oval window Vestibular Canal Helicotrema Cochlear duct Organ of Corti Basilar membrane Traveling wave Hair cells Tectorial membrane Tinnitus Nerve deafness/ Conduction deafness Cochlear implants Bone conduction Auditory Nerve Frequency tuning curve Cochlear nucleus Superior/Inferior colliculus Auditory cortex Tonotopic organization