Autonomic reflexes help regulate internal organs and maintain homeostasis. This lesson explains how the pupillary light reflex works and how forebrain structures—especially the hypothalamus and amygdala—coordinate autonomic responses.
A visceral reflex is an automatic response involving sensory input from an organ or tissue and autonomic motor output to an organ. Its afferent branch carries sensory information toward the central nervous system (CNS), while its efferent branch carries commands from the CNS to a target.
All flashcards
What are the afferent and efferent branches of a visceral reflex?
The afferent branch carries sensory information toward the CNS. The efferent branch carries autonomic commands from the CNS to an organ or other target.
What is the bilateral pupillary light reflex?
When light enters one eye, both pupils constrict. The response occurs in both eyes even though the stimulus is presented to only one.
How does bright light produce pupil constriction?
Retinal input reaches central control pathways, and parasympathetic output travels through the oculomotor nerve and ciliary ganglion to contract the iris's circular muscles.
What is autonomic tone?
It is the ongoing level of organ activity resulting from the balance between sympathetic and parasympathetic input.
How can the amygdala affect autonomic activity?
The amygdala can signal the hypothalamus through the medial forebrain bundle. During fear or anxiety, this can promote sympathetic fight-or-flight activity and influence stress-hormone release.
Quiz questions
Which information does the solitary nucleus receive through the glossopharyngeal and vagus nerves?Answer: Sensory information about blood pressure and cardiac function.
What happens to both pupils when bright light is shone into only one eye?Answer: Both pupils constrict because the response to the unilateral stimulus is bilateral.
Which function is associated with the dorsal motor nucleus of the vagus?Answer: It contributes to slowing the heart, constricting bronchi, and activating digestive activity.
Which statement describes a contribution of the nucleus ambiguus?Answer: It supplies muscles involved in swallowing and speech and contributes to parasympathetic cardiac control.
Which pattern of autonomic changes commonly supports physical exercise?Answer: Heart rate, breathing, and sweating increase while digestive activity decreases.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.