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Special Senses

Special Senses. Hearing. Hearing. Ear is a very sensitive structure. The sensory receptors convert vibrations 1,000 times faster than the photoreceptors of the eye can respond to light . Structure. Three main regions Outer Ear Collects sounds waves and channels them inward Middle Ear

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Special Senses

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  1. Special Senses Hearing

  2. Hearing • Ear is a very sensitive structure. • The sensory receptors convert vibrations 1,000 times faster than the photoreceptors of the eye can respond to light

  3. Structure • Three main regions • Outer Ear • Collects sounds waves and channels them inward • Middle Ear • Conveys the sound vibrations to the oval window • Inner Ear • Which houses the receptors for hearing and equillibrium

  4. Structure of the Ear

  5. Outer Ear • Consists of: • Auricle • External Auditory canal • Eardrum

  6. Auricle • Part of the ear you see • Structure: • Skin covered flap of elastic cartilage • Function: • Collect sound waves and direct them toward external auditory canl

  7. External Auditory Canal • Structure: • Two structures help keep out invaders • Few Hairs • Ceruminous gland • Secret cerumen (earwax) • Function: • Curved tube directs sound waves toward the eardrum

  8. Eardrum • A.k.a. Tympanic membrane • Structure: • Thin, semitransparent partition between external auditory canal and the middle ear • Function: • Changes sounds waves into vibrations

  9. Middle/Inner Ear

  10. Middle Ear • Small, air-filled cavity between eardrum and inner ear • Consists of • Auditory tube • Auditory ossicles

  11. Auditory Tube • Opening in the anterior wall of the middle ear leads to auditory tube (Eustachian tube) • Connects the middle ear to upper portion of throat • When it is open, air pressure equalizes on both sides of the eardrum • When closed – if air pressure builds the eardrum can rupture • Swallowing or yawing opens up the auditory tube

  12. Auditory Ossicles • 3 tiny bones span across the middle ear by means of ligaments • Malleus • Incus • Stapes • Forms a small opening, oval window, where the inner ear begins • Function • To pass the vibration from the outer ear to the inner ear

  13. Ossicles

  14. Inner Ear • Divisions • Bony Labyrinth • Series of cavities in the temporal bone, including the cochlea, vestibule, and semicircular canals • Contains a fluid called perilymph • Inner membranous labyrinth • Series of sacs and tubes with the general shape as the bony labyrinth • Contains a fluid called endolymph

  15. Bony Labyrinth • Cochlea • Sense organ for hearing • Semicircular canals and vestibule • Sense organs for balance and equilibrium

  16. Inner Ear

  17. Process of Hearing • Auricle directs sound waves to external auditory canal • External auditory canals continues to direct sounds waves to the eardrum • Eardrum converts sound waves into vibrations • Eardrum vibrates the malleus • Malleus vibrates the incus then to the stapes • Stapes move back and forth and pushing oval window in and out • Movement of oval window sets up the fluid pressure waves in the perilymph of the cochlea • Fluid pressure waves build and eventually cause the endolymph to transmit waves to the hairs inside the cochlea • Hairs are stimulated they release neurotransmitter molecules, change waves into electrical impulses • Electrical impulses to the brain through the auditory nerve

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