29.3 The Senses SLO: You will be able to explain the anatomy of the ear as well as hearing physiology and its disruption during hearing loss. Essential Question: How do our ears detect stimulation from our internal and external environments. Science Trivia There are 3,500 inner and 12,000 outer hair cells in the cochlea that contain mechanoreceptors for hearing. The hand has 17,000 mechano­receptors.

29.3 The Senses Vocabulary pinna tympanic membrane cochlea semi- circular canals vestibulocochlear nerve –auditory nerve hair cell –cilia –stereocilia mechanoreceptor ossicles - malleus - incus - stapes stapedius tensor tympani oval window eustachian tube

29.3 The Senses Cranial Nerves- Emerge directly from the brain Axons extend beyond the brain

13.1 Ecologists Study Relationships The “Ear” is housed within the TEMPORAL BONE

29.3 The Senses The ear contributes to hearing. Tympanic Membrane

29.3 The Senses 3 Parts of the Ear Outer, Middle, and Inner Ear Part 1 OUTER EAR- From the Pinna to Tympanic Membrane

29.3 The Senses Outer Ear Structures: Pinna – cartilaginous, highly variable in appearance, some landmarks. External Auditory Canal- (or external auditory meatus), 2.5 cm tube.

29.3 The Senses Pinna Landmarks Helix Antihelix Concha Tragus Intertragal Notch Antitragus

29.3 The Senses External Auditory Canal 2 Parts: lateral portion-cartilage –hairs in lateral part –cerumen (ear wax) secreted in lateral part. medial portion-osseous –lined with epidermal (skin) tissue

29.3 The Senses Outer Ear Functions 1)Amplification / Filtering - makes sound waves stronger - amplifies sound waves 2) Protection - depth of the canal, shape, and rigid walls provides protections of the middle/inner ear from direct injury - wax helps to prevent objects from entering the ear canal and aid in the shedding and migration of skin out of the canal 3) Localization - Restriction/limited to the outer ear

29.3 The Senses Does Ear Wax Have a Purpose? 2 important functions 1.Keeps skin in ear canal soft 2. Keeps bugs out (they don’t like the taste)

29.3 The Senses The Middle Ear: Lining is mucous membrane Tympanic membrane separates it from EAC Eustachian tube connects it to nasopharynx Also connected to Mastoid Air Cells -located within a cleft within the temporal bone

29.3 The Senses Middle Ear Structures 1- Malleus 2- Incus Ossicles 3- Stapes ( Oval Window located beneath stapes) 4- Tympanic Membrane (Eardrum) 5- Round Window 6- Eustachian Tube

29.3 The Senses Tympanic Membrane Healthy TM is translucent is silvery in color Ljkancjbvakjbad svjvbakvjhzvcjvj acvjhzv

29.3 The Senses Ossicles= 1) Malleus, 2) Incus, and 3) Stapes 3 smallest bones in the body

29.3 The Senses The 3 ossicles vibrate - stapes comes into direct contact with the Oval Window - causes a disturbance malleus stapes incus

29.3 The Senses Eustachian Tube What is the purpose? 1)Drain cells/tissue -Clears mucus 2)Equalize air pressure 3)Protects the middle ear from unwanted pressure fluctuations and loud sounds

29.3 The Senses Middle Ear: Functions Transmission –Sound waves change to mechanical energy in the middle ear -Energy associated with motion (vibration) and position Filtering –Acoustic reflex decreases the transmission of mechanical energy to the cochlea

29.3 The Senses Middle Ear Muscles 1)The Stapedius –a ttaches to stapes –contracts in response to loud sounds, chewing, speaking –Innervated by the facial (VIIth cranial) nerve –DAMPENS THE MOVEMENT of STAPES BONE 2) The Tensor Tympani - h elps open Eustachian tube - innervated by V cranial nerve Eustachian tube

29.3 The Senses Entrance to the Inner ear

29.3 The Senses The Inner Ear Structures 1)Cochlea 2) Semi- circular canals 3) Vestibulocochlear nerve (8 th cranial nerve- auditory nerve) Note the changes of energy as the sound waves come through each part of the ear

29.3 The Senses Semicircular Canals –Vestibular part –Transduces motion and pull of gravity Cochlear –Auditory part –Transduces sound energy to electrical energy Both Contain Hair Cells INNER EAR FUNCTIONS

29.3 The Senses The COCHLEA Size of a pea Fluid –filled Contains up to 20,000 hair cells (body-cilia- stereo cilia) –hair cells are mechanoreceptors –Sensory receptors that respond to mechanical pressure or distortion –Hair cells bend in response to vibrations

29.3 The Senses Cochlea

29.3 The Senses Transduction- Converting mechanical energy into electrical energy. − Each hair cell has a small patch of cilia with stereocilia on its apex − Movement of the fluid by ossicles stimulates the cilia & stereocilia to move −Creates electrical impulses − If the sound is too loud, the stereocilia can be bent or broken −Dead/damaged hair cell can no longer send sound signals to the brain, do not regenerate

29.3 The Senses Vestibulocochlear nerve- carries electrical impulses from cilia (in cochlea and semicircular canals) to the brain for interpretation

29.3 The Senses Review--Pathway of Sound Sound waves enter pinna travel through the auditory canal Sound waves strike tympanic membrane causing vibrations (mechanical energy) Vibrating TM causes ossicles to vibrate Vibrating stapes bone at oval window generates movement of cochlear fluid Fluid movement stimulates cilia-lined cochlea Cilia sends electrical impulses along vestibulocochlear nerve (auditory nerve) to brain for interpretation

29.3 The Senses Submit your take home quiz Do Now

29.3 The Senses Conductive Hearing Loss Otitis externa Otitis media Otosclerosis Congenital Sensorineural Hearing Loss Vocabulary

29.3 The Senses Gauging Prior Knowledge Was there a time where you had an "ear infection." How do you think this occurred? What caused it? How did it go away?

29.3 The Senses CONDUCTIVE HEARING LOSS Any hearing loss occurring in the OUTER or MIDDLE EAR Examples……. –Malformed pinna –Too much wax –Swimmers ear/infection of outer ear –Torn tympamic membrane –Otitis media/infection of middle ear –Otosclerosis -abnormal growth of bone of the middle ear. This bone prevents structures within the ear from working properly and causes hearing loss. –Torn muscles that control the ossicles

29.3 The Senses Conductive Hearing Loss can be repaired** -surgical repair - if ear structures cannot be corrected… hearing aids may be used to amplify sounds at preset frequencies to overcome a conductive hearing loss in that range CONDUCTIVE HEARING LOSS

29.3 The Senses What Causes Outer Ear Hearing Loss ? Wax pushed up against eardrum (tympanic membrane) from q-tip use  Sharp objects that puncture tympanic membrane Born with damaged ear canal or without pinna Swimmer’s Ear/Otitis Externa - what is that?

29.3 The Senses Swimmer’s Ear Water/moisture + Germs or bacteria + injury to tissue in the auditory canal = infection  Complications –Decreased or muffled hearing –Temporary hearing loss –Deep tissue infection –Bone/Cartilage Damage Treatment - Ear drops-Antibiotics - (Steroids for inflammation)

29.3 The Senses What Causes Hearing Loss in the Middle Ear ? Loud sudden noises- firecracker, gunshot Trauma to the head- fall, car accident Middle Ear Infection/Otitis media…

29.3 The Senses Otitis Media Most common ailment for children- Why??? –D–Drainage –I–Immune system Germs travel up eustachian tube- lodge in middle ear Red or pink or bulging shows an infection.

29.3 The Senses Why is it a concern? Ossicles do not vibrate correctly = 25dB hearing loss Critical time for learning langauge Treatments –antibiotics

29.3 The Senses Chronic Otitis Media- (Persistent/Long Lasting) Ear Tubes- Small slit made in TM and tube put in for drainage from Middle Ear- most tubes fall out after a few months

29.3 The Senses Sensorineural Hearing Loss=(Hearing loss in the Inner Ear) What Causes Hearing Loss in the Inner Ear ? Examples- Inherited Abnormal development in the fetal stages of life Premature birth Trauma -membrane rupture - Airbag -(ruptures tympanic membrane) Multiple Sclerosis Bacterial infection Ototoxic drugs (aspirin) Tumor Noise explosion Meniere’s disease -abnormal composition of fluid Congenital (present at birth) or Acquired (develops after birth)

29.3 The Senses Why do you get dizzy? Vestibular Liquid in Semi –Circular canals Information from cilia sent to brain Must match info sent from eyes Dizzy = brain doesn’t know what to follow

29.3 The Senses Checking our understanding-Vestibular System Group Work (Pairs) Using your computers, answer the following questions. Please write the questions on a sheet of paper. 1)What is the vestibular system? 2)List the structures that make up the vestibular system. 3)List a disorder of the vestibular system.