- Ear Anatomy chapter 11

-outer ear : sight of nervous stimulation ; collects sound waves , transmit to mid and inner ear

-structure

• pinna : collects sound

• external auditory canal (has a meatus of 2.5 cm ) and leads into middle and inner ear

• ceruminous glands : modified suderdifiours / sweat that produce wax / cerumen

• Tympanic membrane : ear drums , vibrates

-Middle ear : 3 ossicles ; conduct sound waves and transmit to inner ear where hearing receptors are located

• Malleus : hammer ; attached to tympanic membrane

• Incus : anvil ; connected to malleus

• Stapes : stirrup ; touches bony labyrinth

  • bony labyrinth : the rigid, bony structure that houses the membranous labyrinth within the inner ear. outer shell of the inner ear

  • Equilibrium receptors : vestibule

• Auditory ( eustachian ) tube : canal that connects meso ear to nasopharynx. controls pressure of meso ear and equlazes to external canal

- Conductive hearing loss : sound waves cannot get into inner ear due to maybe blockage , membrane , or a separate ossicular issue

-Inner ear

• Utricle : responds to horizontal acceleration in forward direction

• Otoconia crystals + gel membrane : made of calcium carbonate gives opposite direction of motion on hair cells using stereocilia

  • ion channels on stereocilia depolarize and start an action potential signal

  • When the gel membrane moves, the cilia bend, causing ion channels to open.

-vestibulocochlear is cranial nerve 8

Saccule : senses vertical movement as in tilting head down / up

otolithic membrane : pushes stereocilia on hair cells forward when looking down

- Inner ear

• Bony labyrinth's semi - circular canals: part of vestibular apparatus and senses rotation

• 3 semicirular canals have an area called ampullae

  • Crista ampullaris sensory organ : hair cells + cilla extending out of gelatinous culpa

  • Afferent sensory axon synapse with hair cells

-when spinning ; Endolymph fluid flows in opposite direction of rotation and pushes the cupula and cilla

• afferent depolarization

-lateral canal : sense left and right head rotation

-posterior canal : rotation for right ear to touch right shoulder - neck flexion

- anterior canal : up and down

-Organ Corti : transduce mechanical sound waves into nerve impulses

• sound waves from stapes enter oval window of cochlea ( apart of bony labyrinth ) to perilymph

  • perliymph fluid : basilar membrane up and down

  • basilar membrane becomes more stiff with more force based on different pitch making tectorial membrane to move back and forth