This lesson introduces the two functional parts of the nervous system and explains how the autonomic nervous system helps maintain internal balance.
The nervous system can be divided functionally into the somatic nervous system and the autonomic nervous system. They differ chiefly in the tissues they control and the kinds of responses they produce.
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What does the somatic nervous system control?
It causes contraction of skeletal muscle. Its actions are often voluntary, although some can occur without conscious awareness.
What does the autonomic nervous system control?
It regulates cardiac muscle, smooth muscle, and glandular tissue, primarily through involuntary activity.
What is the general role of the sympathetic division?
It coordinates body changes associated with responding to challenges, commonly summarized as fight or flight.
What is the general role of the parasympathetic division?
It supports routine maintenance, digestion, and recovery, commonly summarized as rest and digest.
What is dual innervation?
It is the arrangement in which an organ receives input from both sympathetic and parasympathetic divisions, which can have different effects on its activity.
Quiz questions
Where do sympathetic preganglionic neurons originate?Answer: The thoracic and upper lumbar spinal cord
Which branch carries myelinated preganglionic fibers into the sympathetic chain?Answer: The white ramus communicans
About how many targets may one sympathetic preganglionic neuron influence through divergence?Answer: Approximately 10–20 targets
Which cells receive sympathetic preganglionic fibers in the adrenal medulla?Answer: Chromaffin cells
What signaling molecule do most sympathetic postganglionic fibers release?Answer: Norepinephrine
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.