1. Senses: Hearing and Equilibrium
Ch. 17-3

2. Hearing Anatomy of the ear External ear Middle ear Inner ear
Collects sound waves and channels them inward
Middle ear
Conveys sound vibrations to the oval window
Inner ear
Houses the receptors for hearing and equilibrium

3. Ear Anatomy

4. Outer Ear
Auricle (pinna) – flap of elastic cartilage shaped like a trumpet
External auditory canal – curved tube that lies in the temporal bone and leads from the auricle to the eardrum
Eardrum (tympanic membrane) – thin, semitransparent partition between the external auditory canal and the middle ear
Ceruminous glands – produce wax to protect ear from dust and foreign objects

5. Outer Ear

6. Middle Ear Small, air-filled cavity
Contains 3 smallest bones in the body
Auditory ossicles
Malleus, incus, and stapes
contains auditory tube (eustachian tube) – connects middle ear to the throat and nasal cavities
Helps maintain air pressure
Can lead to ear pain during sore throats

7. Middle Ear

8. Inner Ear Labyrinth – communicating chambers and tubes Contains
Semicircular canals – sense of equilibrium
Cochlea – sense of hearing
Organ of Corti – contains hearing receptors, hair cells detect vibrations
Turn pressure waves into electrical signals to the brain

9. Inner Ear

10. Hearing Pinna directs sound waves into auditory canal
Sound waves strike ear drum and it vibrates
Auditory ossicles amplify vibrations to cochlea
Organs of Corti contain receptor cells (hair cells) that deform the vibrations
Impulses sent to nerves
Temporal lobe interprets sensory impulses

11. Hearing

12. Equilibrium Balance – 2 types
Static – maintenance of body relative to gravity
Dynamic – maintenance of body in response to sudden movements like rotation, acceleration, and deceleration
Organs that control this are called the vestibular apparatus – all lined with hairs
Saccule and utricle
Semicircular ducts (canals)

13. Equilibrium
The hair cells send signals to the brain that tell it the position of the head
As the hair cells move, the brain can interpret and fix balance