Physiology

PhysiologyHearing = neural perception of sound energy Aspect : what and whereSound waves : traveling vibration of air, consist of region of high pressure (caused by compression of air molecules) alternating with regions of low pressure (caused by rarefaction of the molecules)(disturbance pattern in air molecule produces sound)Media : air, waterin water require greater pressures to cause this disturbanceRarefaction = penjernihan, penghalusan2Gambar 6-32, table 6-5Sound waves :Pitch (tone) determined by the frequency of vibrationIntensity (loudness) depends on the amplitude of sound waves (pressure difference between high and low pressure)measured in decibels (dB) logarithmic measure of intensity compared w/ the hearing thresholdTimbre (quality) : sound depends on its overtonesTunig fork has a pure tone, most sounds lack of purityComplex mixture of overtones different sounds to different instruments playing the same note (ex : trumpet and piano)Overtones responsible for characteristic differences in voicesWe can tell whether it is our mother or girlfriends voiceExternal ear plays a role in sound localizationReceptors (for sound) in the fluid-filled inner ear.Function of External & Middle ear : airborne sound waves be channeled into inner ear, compensating loss of sound energy when pass from air into water.Pinna (relative immobile) : collects sound waves, and channels them down the MAE.Partially shield sound waves that approach the ear from the rear changing the timbre of sound & distinguish sound from in front or behind.From right or left determined by 2 cues :The sound wave reaches the closer ear slightly before it arrives at the farther ear.The sound is less intense at the farther ear (head acts as a sound barrier partially disrupts the propagation of sound waves)Cortex of auditory determine the location of the sound source, by differences in the timing of neural firing patterns (bukan seperti mata yg mengetahui lokasi benda dari hasil proyeksi perhitungan dari objek ke retina).One ear difficult to localize the sound.Hair and earwax : prevent from airborne particles from reaching the inner portion (could accumulate or injure the tympanic membrane).

External ear plays a role in sound localizationTympanic membrane vibrates in unison with sound waves in the external earHigher and lower pressure regions of sound wave eardrum bow inward and outward in unison with waves frequency.The resting air pressure on both side of tympanic membrane must equal For the membrane to be free to move as sound waves strike it.The middle ear bones convert tympanic membrane vibrations into fluid movements in the inner earVibratory movements of tympanic membrane ossicular chain (malleus, incus, stapes), that is set into motion at the same frequency oval window (same freq as original sound waves) entrance into fluid-filled cochlea (greater pressure is required to set fluid in motion).Tympanic membrane has much larger surface area than oval window pressure is increased as force exerted on tympanic membrane is conveyed by ossicles to oval window.The lever action of the ossicles provides an additional mechanical advantage. Increase the force/pressure on the oval window 20x motion of cochlear fluidThe middle ear bones convert tympanic membrane vibrations into fluid movements in the inner earLoud sounds (>70dB) muscles in middle ear contract reflexly (40msec after exposure) tympanic membrane tighten & limiting movement of the ossicular chain reduced movement of middle ear structure diminished loud sound waves to inner ear (protect the delicate sensory apparatus from damage from prolonged loud sound, not from sudden loud sound, like explosion).Organ of Corti, the sense organ of hearingHair cells in the Organ of Corti transduce fluid movement into neural signals Pitch discrimination depends on the region of the basilar membrane that vibratesLoudness discrimination depends on the amplitude of vibrationThe auditory cortex is mapped according to toneDeafness is caused by defects either in conduction or neural processing of sound wavesSensory system of Inner ear house :Cochlea : sound waves nerve impulseVestibular apparatus : sense of equilibriumEquilibriumvestibular apparatusVestibular apparatus = sense of equilibrium and coordinating head movementConsists of two sets of structures : (gambar 6-38a) nj8uSemicircular canalsOtolith organs (utricule and saccule)Detects changes in position and motion of the headEach contain hair cells respond to mechanical deformation triggered by specific movements of the endolymphDepolarized or hyperpolarized depending on the direction of the fluid movementMuch of this information doesnt reach the level of conscious awarenessSemicircular canalsDetect rotational or angular acceleration or deceleration of the head, such as when starting or stopping spinning, somersaulting, or turning the headReceptive hair cells located at ampullaThese hair cells are embedded in cupula (caplike, gelatinous layer, which protrudes into the endolymph) gambar 6-38bCupula sways in the direction of fluid movement (just like seaweed in the tide) gambar 6-39Somersaulting = jungkir balik, embedded = tertanam, protrude menonjol, tide = gelombang laut17Hairs of vestibular hair cell consist ofOne cillium = kinocillium20-50 microvilli = stereociliaTersusun dengan ketinggian tidak sama (gambar 6-38 c)

Gambar 6-38 dOtolith organs