1. The nervous system: the ear
Emily Torres
Ariana Soto
Per: 5

2. Sense of Hearing The Ear enables us to be able to: - hear sound waves
- have sense of equilibrium
The Ear is composed of the:
- Outer (External) Ear
- Middle Ear
- Inner (Internal) Ear

3. Outer (External) Ear The Outer Ear consists of these structures:
- Auricle (Pinna)
- External Auditory Canal
- Tympanic membrane
The opening before the temporal bone, there are hairs that guard the canal and skin that contains ceruminous glands.
- Ceruminous glands secrete cerumen (wax)
- wax helps keep foreign particles out

4. Middle Ear The middle ear consists of these structures:
- tympanic membrane
- auditory ossicles:
i. Malleus
ii. Incus
iii. Stapes
- oval window
- tensor tympani
- stapedius

5. Malleus, incus, & stapes
These three bones connect the tympanic membrane and inner (internal) ear by tiny ligaments
Malleus
- vibrates at the same time as tympanic membrane, then causing the incus to vibrate
Incus
- vibrates and sends the vibrations on to the stapes
Stapes
- vibrates and sends a fluid into the inner ear through the oval window

6. Tensor tympani & stapedius
- connected to the wall of the auditory tube
- pulls malleus inward when contracted
Stapedius
- pulls the stapes outward
These involuntary actions are part of the effectors in the tympanic reflex

7. Tympanic reflex
Occurs in about 1/10th of a second after a loud sound in order to protect the hearing receptors from possible damage from a loud external noise
- also occurs when a person is simply talking or singing

8. Auditory tube & Ear pressure adjustment
Connects each middle ear to the nasopharynx
Helps provide equal air pressure on each side of the tympanic membrane

9. Ear Infections Infection of the middle ear
Most common ear infection is otitis media and is usually a result from:
- common cold
- flu
- allergies
- sinus infection

10. Inner (Internal) ear Structures include; Cochlea Semicircular canals
Vestibule

11. cochlea
Fluid filled snail-like structure that contains the receptor organ for hearing
Spiral organ of Corti
Divided into 3 chambers
Contains hair cells
2 types of fluid
Perilymph
Endolymph

12. Cochlea Chambers Scala Vestibuli-
Perilymph (provides cushioning support, similar to interstitial fluid)
Scala Media-
Endolymph
Organ of Corti
Scala Tympani-

13. Organ of corti Found on basilar membrane in the scala media chamber
Sensory organ of hearing
Sound sensitive hair cells
Pressure change causes hair cells to bend and stimulate a nerve signal which is carried to the brain
This is how sound can be recognized

14. Semicircular Canal Body’s balance organ
3 canals (superior, horizontal, and posterior) filled with endolymph that are each responsible for detecting motion on a different plane
Sense head rotations/movement

15. Vestibule Senses movement Holds 2 sacs of fluid
 the ultricle & the saccule
Hair cells
Macula
Known as gravity receptors

16. Equilibrium State of balance
Condition in which contending forces are equal
2 types:
Static
Dynamic

17. Static equilibrium
Occurs when the body is motionless or moving in a straight line
Maintains stability and posture
Entrance of inner ear is the Vestibule
Vestibule contains 2 sacs of fluid (Ultricle & Saccule)
The maculae of the ultricle and saccule are the gravity receptors that respond to linear acceleration, deceleration, and position in space
Otoliths are calcium carbonate particles found in the fluid
When your head moves, the otoliths bursh against the hair cells that line the utricle & saccule
Sends message to brain

18. Static equilibrium diagram

19. Dynamic equilibrium
Occurs when the body is moving in a rotational or angular direction (spinning)
Detects motion
Sense of balance is interpreted in the Semicircular Canals
Ampullae, the organs of dynamic equilibrium, are located at the base of each semicircular canal
A gelatinous cupula is found in the ampullae
Hair cells found on the cupula respond to movement
When head rotates, endolymph moves and flows into the ampulla and causes the cupula to bend which triggers the hair cells to send messages to the brain

20. Dynamic equilibrium diagram

21. Sound collection & pathway through the ear canal
The Auricle (Pinna)
- collects sound waves in the air, then sends them into the auditory canal
The Auditory Canal
- once sound waves enter here and pass to the end of the canal, they alter pressure on the tympanic membrane
The Tympanic Membrane
- moves back and forth due to sound waves, which then makes the vibrations

22. Malleus, incus, & stapes (ossicles)
These three bones connect the tympanic membrane and inner (internal) ear by tiny ligaments
Malleus
- vibrates at the same time as tympanic membrane, then causing the incus to vibrate
Incus
- vibrates and sends the vibrations on to the stapes
Stapes
- vibrates and sends fluid into the inner ear through the oval window

23. (Continued) The Oval Window
- is an opening that transmits pressure waves of sound into the cochlea
The Round Window
-waves move to the round window and it releases pressure caused by the vibrations of the stapes in the oval window
The Cochlea
- sound waves make fluid in cochlea move and trigger the hair cells to move as well. The hair cells located on the organ of corti separate the sound waves according to their frequencies

24. (Continued) The Auditory Nerve
- hair cells cause an electrical signal to travel through the auditory nerve and to your brain
The Brain
- the brain responds to these separate frequencies and makes a complete sound from them

25. Sources:
"Audition: Hearing, the Ear, and Sound Localization - Boundless Open Textbook." Boundless. N.p., n.d. Web. 30 Apr
"How We Hear A Sound?" YouTube. YouTube, n.d. Web. 30 Apr
"Ear Ossicles." Ear Ossicles. N.p., n.d. Web. 30 Apr
"Hearing and the Cochlea - Anatomy Video: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine, n.d. Web. 30 Apr
"Sense of Balance." Flashcards. N.p., n.d. Web. 30 Apr
"The Cochlea - HowStuffWorks." HowStuffWorks. N.p., n.d. Web. 30 Apr
"Middle Ear." Middle Ear Anatomy, Function & Diagram. N.p., n.d. Web. 30 Apr
"Ear Infection Facts: Causes, Acute Infections, Chronic Infections, and More."WebMD. WebMD, n.d. Web. 30 Apr
"Pharyngotympanic Tube." Eustachian Tube Function, Anatomy & Diagram. N.p., n.d. Web. 30 Apr
"See Pictures of Ear Infection Causes, Symptoms and Treatment."MedicineNet. N.p., n.d. Web. 30 Apr
"Anatomy of the Ear." Anatomy of the Ear. N.p., n.d. Web. 30 Apr