Special Senses: Hearing & Balance Review Ear anatomy Sensory organs for Hearing: _____________ Balance: Otolith organs (saccule and utricle) and 3 semicircular canals Organ of Corti Fig. 10.18

Sound transmission Sound waves Tympanic membrane vibrations Ossicles transmit & amplify vibration Via oval window to perilymph then endolymph 1

cont. Vibrations in endolymph stimulate receptor cells NT release of receptor cell stimulates nearby sensory neuron Impulse to auditory cortex of temporal lobe via ________________ nerve Fig 10-18 2

Interpretation of Sound Waves: Pitch Perception Sound wave frequency expressed in Hertz (Hz) = wavelength / sec Human can hear between 20 and 20,000 Hz High pitch = high frequency Low pitch = low frequency Tone = pure sound of 1 frequency (e.g. tuning fork)

Basilar Membrane Pitch perception is function of basilar membrane BM stiff near oval window BM more flexible near distal end Brain translates location on membrane into pitch of sound →Temporal aspects of frequency are transformed into spatial coding → Spatial coding is preserved in auditory cortex

Effects of different sound pitches on the basilar membrane Fig 10-20

Interpretation of Sound Waves: Loudness perception Rate at which APs are fired   loudness  Sound Intensity Measurement: Decibel Scale (dB) starts at 0 and is logarithmic 130 dB pain threshold > 80 dB frequently or prolonged  ? Examples: noisy restaurant ~ 70 dB rock concert ~ 120 dB

conductive hearing loss sensorineural hearing loss Hearing loss that results from damage to the structures of the inner ear is called _________. central hearing loss conductive hearing loss sensorineural hearing loss

Three Types of Hearing Loss Conduction deafness: Damage to _______or _______ear. Many possible etiologies (?) Sensorineural (perceptive) deafness: Damage _______ear. Most common: gradual loss of receptor cells Central deafness: Damage to _____________ or cortical cells. Age related: ________________ Presbycussis External or middle ear. Otitis media, otosclerosis etc…. Inner ear Neural pathways Fig 10-21 3

near the stiff and narrow proximal end Low frequency sound waves create the maximum displacement ______________________ of the basilar membrane. near the stiff and narrow proximal end near the flexible and wide distal end in the middle near the oval window both A) and D) are correct b

taller more frequent less frequent shorter broader Louder noises result in ____________ action potentials in the sensory neuron taller more frequent less frequent shorter broader

Equilibrium = State of Balance Utricle and saccule (otolith organs) with maculae (sensory receptors) for linear acceleration and head position Semicircular canals and ampullae with cristae ampullaris (sensory receptors) for rotational acceleration Important besides inner ear: input from vision & stretch receptors in muscle

Motion Sickness Due to sensory input mismatch = Equilibrium disorder Not in book Motion Sickness = Equilibrium disorder Due to sensory input mismatch Example? Antimotion drugs (e.g.: Dramamine): Depression of vestibular inputs 4