1. Human Anatomy & Physiology I
Special Senses
Human Anatomy & Physiology I
Dr. Rivera

2. Anatomy of the Ear

3. Anatomy of Cochlea
cochlea has three fluid-filled chambers separated by membranes:
scala vestibuli – superior chamber
filled with perilymph
begins at oval window and spirals to apex
scala tympani – inferior chamber
begins at apex and ends at round window
secondary tympanic membrane – membrane covering round window
scala media (cochlear duct) – triangular middle chamber
filled with endolymph
separated from:
scala vestibuli by vestibular membrane
scala tympani by thicker basilar membrane
contains spiral organ - organ of Corti - acoustic organ – converts vibrations into nerve impulses

4. Cochlea, and Spiral Organ
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Oval window
Figure 16.13
Vestibular
membrane
Cochlear duct
(scala media)
Spiral ganglion
Cochlear nerve
(a)
Scala vestibuli
(with perilymph)
Vestibular
membrane
Tectorial
membrane
Cochlear duct
(with
endolymph)
Hairs
(stereocilia)
Scala tympani
(with perilymph)
Outer
hair cells
Supporting
cells
Tectorial
membrane
Basilar
membrane
Spiral
organ
Inner hair
cell
Basilar
membrane
Fibers of
cochlear nerve
(b)
(c) 4

5. Spiral Organ (Organ of Corti)
The spiral organ has epithelium composed of hair cells and supporting cells
The hair cells have long, stiff microvilli called stereocilia on apical surface
gelatinous tectorial membrane rests on top of stereocilia

6. Organ of Corti Inner Ear
16-6 6

7. Physiology of Hearing
The auricle directs sound wanes into the external auditory canal.
When sound waves strike the eardrum, the alternating high and low pressure of the air causes the eardrum to vibrate back and forth. The eardrum vibrates slowly in response to low-pitched sounds and rapidly in response to high-pitched sounds.

8. Physiology of Hearing
3. The central area of the eardrum connects with to the ossicles. The vibration is transmitted from the malleus to the incus and then to the stapes.
4. As the stapes moves back an forth, it pushes the membrane of the oval window in and out.

9. Physiology of Hearing
5. The oval window vibrates about 20 times more vigorously than the eardrum (because the ossicles are very efficient at transmitting the vibrations).
6. The movement of the oval window sets up fluid pressure waves in the perilymph. As the oval window bulges inward, it pushes on the perilymph of the scala vestibuli.
7. Pressure waves are trasmitted from the scala vestibuli to the scala tympani and eventually to the round window, causing it to bulge outward into the middle ear.

10. Physiology of Hearing
8. As the pressure wave deform the walls of the scala vestibuli and tympanic, they also push the vestibular membrane back and forth, creating pressure waves in the endolymph inside the cochlear duct.

11. Physiology of Hearing
9. The pressure wave in the endolymph cause the basilar membrane to vibrate, which moves the hair cells of the spiral organ against the tectorial membrane.
10. Bending of the stereocilia produces receptor potentials that ultimately lead to the generation of nerve impulses.

12. Potassium Gates Figure 16.16 16-12 12 Unstimulated Stimulated Tip link
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Unstimulated
Stimulated
Tip link
Mechanically
gated K+
channel
Stereocilia K+
Surface of
hair cell K+
K+ gate
closed
K+ gate
open
Figure 16.16
16-12 12

13. Equilibrium
Equilibrium – coordination, balance, and orientation in three-dimensional space
Static equilibrium – the perception of the orientation of the head when the body is stationary
Dynamic equilibrium - perception of motion or acceleration
linear acceleration - change in velocity in a straight line (elevator)
angular acceleration - change in rate of rotation (car turns a corner)

14. Anatomy of the Eye

15. Retina