ear

Senses 

1. Be able to label the ear; identify which parts are associated with the outer, middle, and inner ear; know the functions 

   1. auricle/pinna

• Collects sound waves and funnels them into the ear

• Poorly directs sound waves to the external auditory canal

• External ear 

2. Auditory canal/external auditory meatus 

• Channels sound waves towards the eardrum 

• Sound waves funnel down and are amplified 

• Acidity helps protect against infections, secretes ear wax to prevent canal from drying out and repels insects

• External ear 

3. Eardrum/tympanic membrane 

• Vibrates when hit by sound waves and transfer vibrations to the ossicles

• Sound waves from external auditory canal hit this membrane and cause it to vibrate

• Reproduces frequency and forms sound wave  

• Middle ear 

4. Auditory ossicles include malleus (hammer), incus (anvil), stapes (stirrup) 

• Mechanical linkages between tympanic membrane and inner ear 

• Deliver sound vibrations to inner ear fluids 

• Amplify airborne sounds by 30 dB

• Middle ear 

5. Which one hits the oval window

• Stapes hits the oval window 

6. Auditory tube/eustachian tube

• Equalizes air pressure on either side of the eardrum  

• Allows drainage of normal and deceased middle ear secretions

• Middle Ear 

• Connects middle ear to the throat 

• Maintains air pressure

7. Labryinith 

• Communicating chambers and tubes that include: 

1. Vestibule utricle & saccule 

• Membranous sacs w/ receptors for sensation of gravity 

• Upright & acceleration to maintain equilibrium 

2. Semicircular canals 

• 3 tubes that detect movement in 3D spaces; sense of equilibrium 

3. Cochlea 

• Converts stimulus from outside environment into nerve impulses for transmission to brain 

1. Why do we lose our hearing 

• Loud noises and aging damage hair cells in inner ear; older people usually can’t hear frequencies that younger people can 

2. Organ of corti 

   1. Located in the center of cochlea

   2. Has microscopic hairs

   3. Shorter, thinner hairs respond to higher frequencies 

   4. Middle, frequencies moves hair around middle of spiral 

   5. Longer, thicker hair pick up lower frequencies 

   6. The more hair cells that vibrate, the louder the sound 

3. Vestibulocochlear or auditory nerve 

   1. Terminates in a center of brain stem near point where pons and medulla are joined

2. Describe the path sound waves take within the ear and are eventually processed by the brain 

   1. Sound waves enter external auditory canal 

   2. Eardrum vibrates 

   3. Auditory ossicles amplify vibrations 

   4. Stapes hits oval window and transmits vibrations to cochlea 

   5. Organ of corti contains receptor cells that deform from vibrations

   6. Impulses sent to the auditory nerve 

   7. Auditory cortex of temporal lobe interprets sensory impulses 

   8. Round window dissipates vibrations within cochlea 

3. Compare static equilibrium with dynamic equilibrium 

• Static equilibrium (vestibule) - maintains stability and posture 

• Dynamic equilibrium (semicircular canals) - balance during sudden movement or rotation 

• Cerebellum - part of brain that interprets impulses from semi circular canals and vestibule and maintains overall balance 

1. What part of the ear maintains your equilibrium 

   1. Semicircular canals

   2. Utricle

   3. Saccule

2. What is the role of the cerebellum in equilibrium