1. 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.

2. 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

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

4. The “Ear” is housed within the
TEMPORAL BONE

5. The ear contributes to hearing.
Tympanic Membrane

6. 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

7. 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.

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

9. 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

10. 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

11. 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)

12. 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

13. (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

14. Healthy TM is translucent is silvery in color
Tympanic Membrane
Healthy TM is translucent is silvery in color
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15. Ossicles= 1) Malleus, 2) Incus, and 3) Stapes
Ossicles= 1) Malleus, 2) Incus, and 3) Stapes 3 smallest bones in the body

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

17. 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

18. 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

19. 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

20. Entrance to the Inner ear

21. 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

22. 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

23. 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

24. Cochlea

25. 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

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

27. 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

28. 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

29. 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

30. 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?

31. 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)

32. 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…

33. 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.

34. 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

35. 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

36. 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

37. 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

38. 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