Page 629 - Fundamentals of anatomy physiology

616 Unit 3 Control and Regulation

Checkpoint part of the temporal bone of the skull. Equilibrium sensations
1 1. If you had been born without cones in your eyes, inform us of the position of the head in space by monitoring
gravity, linear acceleration, and rotation. Hearing enables us to
would you still be able to see? Explain. detect and interpret sound waves.
12. How could a diet deficient in vitamin A affect vision?
1 3. What effect would a decrease in phosphodiesterase The basic receptor mechanism for both senses is the same.
The receptors, called hair cells, are mechanoreceptors. The com-
activity in photoreceptor cells have on vision? plex structure of the internal ear and the different arrangement
of accessory structures enable hair cells to respond to different
See the blue Answers tab at the back of the book. stimuli, providing the input for both senses.

17-5 Equilibrium sensations Anatomy of the Ear

originate within the internal ear, while The ear is divided into three anatomical regions: the external
hearing involves the detection and ear, the middle ear, and the internal ear (Figure 17–21). The
interpretation of sound waves external ear—the visible portion of the ear—collects and directs
sound waves toward the middle ear, a chamber located within
Learning Outcome Describe the structures of the external, middle, and the petrous portion of the temporal bone. Structures of the
internal ear, explain their roles in equilibrium and hearing, and trace the middle ear collect sound waves and transmit them to an ap-
pathways for equilibrium and hearing to their destinations in the brain. propriate portion of the internal ear, which contains the sensory
organs for both hearing and equilibrium.
The special senses of equilibrium and hearing are provided
by the internal ear, a receptor complex located in the petrous

17

Figure 17–21 The Anatomy of the Ear. The dashed lines indicate the boundaries separating the

three anatomical regions of the ear (external, middle, and internal).

External Ear Middle Ear Internal Ear
Elastic cartilages Auditory ossicles

Oval Semicircular canals
window
Petrous part of
Auricle temporal bone

Facial nerve (VII)

Vestibulocochlear
nerve (VIII)

Tympanic Bony labyrinth
cavity of internal ear

Cochlea

Auditory tube
To
nasopharynx

External acoustic Tympanic Round Vestibule
meatus membrane window