1. Nervous System
Ms. Doshi

2. Sensory Division: The Ear
What does the ear do?
Transduces sound energy into impulses.
Responsible for balance.
Memorize the parts of the ear. You have 10 minutes.

3. The Ear: Structure 6 1 2 3 4 11 5 12 8 7 10 9 14 13

4. How do we hear? I Sound wave vibrations enter the ear.
First, they enter the outer ear. The outer ear consists of the pinna and the auditory canal.
At the end of the auditory canal, is the tympanic membrane of the middle ear.
The tympanic membrane vibrates at the same frequency as the sound we hear.
3 bones, or ossicles (malleus, incus, and stapes) amplify the stimulus.

5. How do we hear? II
The stimulus moves through the oval window to the inner ear. The inner ear consists of the cochlea and the semi-circular canals. It contains fluid.
The cochlea contains the organ of Corti, which has hair cells.
When the ossicles vibrate, pressure is put on the fluid in the cochlea.
This pressure causes the hair cells to be stimulated.
The hair cells transduce the pressure into action potentials.
The action potentials travel, through the auditory nerve, to the brain.

6. The Ear and Balance
The three semicircular canals are filled with a fluid called endolymph.
At the base of each canal, is a chamber with sensory hair cells.
The rotation of the head moves endolymph in one of the canals.
This puts pressure on the hair cells and changes the impulses to the brain.
The brain then knows the position of the head.

7. Questions 14