Essential Question: How do the senses detect SLO: You will be able to explain how senses help maintain homeostasis and explain how the senses detect physical and chemical stimuli. Essential Question: How do the senses 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.

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

Cranial Nerves- Emerge directly from the brain Axons extend beyond the brain

The “Ear” is housed within the TEMPORAL BONE

The ear contributes to hearing. Tympanic Membrane

3 Parts of the Ear Outer, Middle, and Inner Ear Part 1 OUTER EAR- From the Pinna to Tympanic Membrane Pinna for humans has a poor design (too flat on head) try “cupping” ears and see how sound quality improves Speed of sound-Speed of sound- at 68 degrees 1,125 feet per second = 756 mph Higher temps= faster speed for sound

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

Helix Antihelix Concha Tragus Intertragal Notch Antitragus Pinna Landmarks Helix Antihelix Concha Tragus Intertragal Notch Antitragus

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

Outer Ear Functions 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

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)

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

(Oval Window located beneath stapes) 4- Tympanic Membrane (Eardrum) 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

Healthy TM is translucent is silvery in color Tympanic Membrane Healthy TM is translucent is silvery in color Ljkancjbvakjbadsvjvbakvjhzvcjvjacvjhzv

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

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

What is the purpose? Drain cells/tissue -Clears mucus Eustachian Tube What is the purpose? Drain cells/tissue -Clears mucus Equalize air pressure Protects the middle ear from unwanted pressure fluctuations and loud sounds

Sound waves change to mechanical energy in the middle ear 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

Middle Ear Muscles The Stapedius attaches 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 - helps open Eustachian tube - innervated by V cranial nerve Eustachian tube

Entrance to the Inner ear

The Inner Ear Structures Cochlea Semi- circular canals Vestibulocochlear nerve (8th cranial nerve-auditory nerve) Note the changes of energy as the sound waves come through each part of the ear Wave to mechcanical to hydralic to electrical

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

Contains up to 20,000 hair cells (body-cilia-stereo cilia) 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

Cochlea

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

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

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

CONDUCTIVE HEARING LOSS Any hearing loss occurring in the OUTER or MIDDLE EAR Examples……. Malformed pinna Too much wax Swimmers ear (or water stuck in 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

CONDUCTIVE HEARING LOSS 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

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?

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)

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…

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

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

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

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

Liquid in Semi –Circular canals Information from cilia sent to brain Why do you get dizzy? 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 Have students spin

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