22-23 Ch 7 Auditory Sensory Perception

• ​Pinna

  • ​cartilage CT

  • ​epithelial tissue

• External auditory canal

  • ​chamber in the temporal bone

  • ​Ceruminous (wax) glands are present

• Tympanic membrane

  • ​Sound waves entering the canal hit the tympanic membrane or eardrum and cause it to vibrate

• Tympanic Cavity​

  • ​small cavity

  • ​opens to the eustachian tube

    • ​The auditory tube connecting the middle ear with the throat

    • Allows for equalizing pressure during yawning or swallowing

      • ear infections

• ​Ossicles (bones)

  • connect the tympanic membrane to the inner ear

    • ​malleus

      • attaches to the tympanic membrane

    • ​incus

    • ​stapes

      • attaches to the oval window

• ​Bony Labyrinth

  • maze of temporal bone that houses the membranous labyrinth

    • perilymph

      • fluid between the bone and the membrane

• ​Membranous Labyrinth

  • a collection of ​membrane-covered bony chambers

  • ​specialized organs and receptors for hearing or balance

    • endolymph

      • fluid within the membrane

​

• ​Vestibule (chamber)

  • oval window​

    • ​ a membrane-covered opening from the middle ear to the cochlea of the inner ear

• ​Cochlea

  • spiraled structure

    • Scala vestibule/vestibular canal

      • perilymph

    • Scala Tympani/tympanic canal

      • perilymph

    • Cochlear duct

      • basilar membrane

        • endolymph

      • Organ of Corti

• tectorial membrane

  • Changes in the fluid caused by the vibrations pull on the tectorial membrane.

• hair cells

  • mechanoreceptors

    • Tectorial membrane bends/pulls on hair cells, causing depolarization.

• cochlear nerve

• Cochlear organization

  • ​stereocilia are organized by height

    • ​different sound waves result in the movement of different hair cells

  • ​high frequencies are at the base and low frequencies near the apex

• The amplitude or wave height determines the loudness of the sound.

• Vibrations from sound waves move the tectorial membrane

  Hair cells are bent by the membrane

  An action potential starts in the cochlear nerve

• ​Relaying to the brainstem

• The thalamus transmits to the auditory cortex of the temporal lobe.

• Temporal Lobe

  • Area of the brain that corresponds to the frequencies detected by the cochlea

Vestibular Apparatus

• Semicircular canals

  • rotational movement

• Saccule and Utricle

  • static and linear motion

• Ampulla - opening of semicircular canals filled with endolymph

  • Crista ampullaris – receptors in the semicircular canals

    • Tuft of hair cells

    • Cupula (gelatinous cap) covers the hair cells

• Saccule and Utricle

  • macula

    • hair cells

    • otolithic membrane

      • gelatinous matrix

    • otoliths

      • protein-calcium granules

• • Sensorineural hearing loss

    • damage to the organ of Corti

      • presbycusis - age-related

      • Noise-induced hearing loss

      • infections

      • head trauma

      • tumors

• Conductive Hearing Loss

  • Sound waves are not reaching the organ of Corti.

    • blockage

    • bony lesions or anatomical malformations

    • Inner ear infection

• Mixed

  • a mixture of both sensorineural and conductive hearing loss

• ​Tinnitus

  • ringing in the ears

    • subjective

      • abnormal nerve activity

    • Objective

      • physiological middle ear muscle spasm

• ​Vertigo

  • ​sensation of spinning or tilting

    • dizziness, mental bewilderment, confusion, nausea

  • Traumatic brain injury

  • Ménière’s Disease

    • too much endolymph is produced