Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 15 - Section 15.3 - Figure 15.9 - Dual Innervation of the Iris - Page 571: 1

Answer

Fig. 15.9:1 In a frightened person, the pupils dilate

Work Step by Step

This is due to a rush of catecholamine neurotransmitters from the sympathetic nervous system ( of the ANS), and the adrenal medulla. In the fight or flight response to fear, threat, or anxiety, the sympathetic nerves from the superior cervical ganglion release release adrenergic neurotransmitters that stimulate the dilator muscles of the iris (pupillae dilators) to contract; the effect is, a greater area of the pupils become exposed (dilation).
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