How could this be helped by taking a decongestant

Test Yourself Before You Continue

1. Describe the structure of the utricle and saccule and explain how linear acceleration results in stimulation of the hair cells within these organs.

2. Describe the structure of the semicircular canals and explain how they provide a sense of angular acceleration.

Fox: Human Physiology, I 10. Sensory Physiology I Text I I © The McGraw-Hill

Eighth Edition Companies, 2003

Chapter Ten

Helix

Auricle

External auditory meatus

Earlobe

Helix

Auricle

External auditory meatus

Earlobe

Semicircular canals

Facial nerve Vestibular nerve

Cochlear nerve Cochlea Temporal bone Round window Tympanic cavity Auditory tube

Tympanic membrane

Tympanic membrane

■ Figure 10.17 The ear. Note the structures of the outer, middle, and inner ear.

Semicircular canals

Facial nerve Vestibular nerve

Cochlear nerve Cochlea Temporal bone Round window Tympanic cavity Auditory tube

Temporal bone

Epitympanic recess

Tendon of-

tensor tym|

Temporal bone

Epitympanic recess

Auditory

(eustachian) tube

Figure 10.18 A medial view of the middle ear. The locations of auditory muscles, attached to the middle-ear ossicles, are indicated.

Tendon of stapedius mu: Pyramid

Tympanip membrane Tympanic cavity

Auditory

(eustachian) tube

Figure 10.18 A medial view of the middle ear. The locations of auditory muscles, attached to the middle-ear ossicles, are indicated.

The fact that vibrations of the tympanic membrane are transferred through three bones instead of just one affords protection. If the sound is too intense, the ossicles may buckle. This protection is increased by the action of the stapedius muscle, which attaches to the neck of the stapes (fig. 10.18). When sound becomes too loud, the stapedius muscle contracts and dampens the movements of the stapes against the oval window. This action helps to prevent nerve damage within the cochlea. If sounds reach high amplitudes very quickly, however—as in gunshots—the stapedius muscle may not respond soon enough to prevent nerve damage.

Scala vestibuli (contains perilymph)

Cochlear duct (contains endolymph)

Scala tympani (contains perilymph)

Apical turn

Apical turn

Scala tympani (contains perilymph)

Spiral organ (of Corti)

Vestibulocochlear nerve (VIII)

To round window

Cochlea Middle turn

Vestibulocochlear nerve (VIII)

Cochlea Middle turn

From oval window Vestibular membrane

Basal turn Basilar membrane

Spiral organ (of Corti)

To round window

■ Figure 10.19 A cross section of the cochlea. In this view, its three turns and its three compartments—the scala vestibuli, cochlear duct (scala media), and scala tympani—can be seen.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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