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The human internal environment is regulated in large measure by the integrated activity of the autonomic nervous system and endocrine glands. Their visceral and homeostatic functions, essential to life and survival, are involuntary. Why the forces of evolution favored this separation from volition is an interesting question. Claude Bernard expressed this idea in sardonic terms when he wrote, “nature thought it prudent to remove these important phenomena from the caprice of an ignorant will.”

Although relatively few neurologic diseases exert their effects primarily or exclusively on the autonomic–neuroendocrine axis, there are numerous medical diseases that implicate this system in some way: hypertension, asthma, and certain dramatic disorders of cardiac conduction, such as ventricular tachycardia, to name some of the important ones. And many general neurologic diseases involve the autonomic nervous system to a varying extent, giving rise to symptoms such as syncope, sphincteric dysfunction, pupillary abnormalities, impotence, diaphoresis, and disorders of thermoregulation. Finally, in addition to their central role in visceral innervation, autonomic parts of the neuraxis and parts of the endocrine system are used in all emotional experience and its display, as discussed in Chap. 25. Furthermore, a wide variety of commonly used pharmacologic agents influence autonomic functions, making them the concern of every physician.

Breathing is unusual among nervous system functions. Although continuous throughout life, it is not altogether automatic, being partly under volitional control. Current views of the central and peripheral control of breathing, and the ways in which it is altered by certain diseases are of considerable interest to neurologists, if for no other reason than the frequency of respiratory failure resulting from neurologic conditions such as coma, cervical spinal cord injury, and neuromuscular diseases. Treatment of the resultant respiratory failure constitutes a most important part of the specialty of neurologic intensive care. Many of these same comments pertain to the function of swallowing, which is largely automatic and continues at regular intervals even in sleep but is also initiated voluntarily. Furthermore, swallowing fails in ways similar to breathing as a consequence of neurologic diseases.

The autonomic and endocrine systems, although closely related, give rise to disparate clinical syndromes so that each is accorded a separate chapter. This chapter deals more strictly with the autonomic nervous system and the next with the hypothalamus and neuroendocrine disorders. The following discussion of anatomy and physiology serves as an introduction to both chapters.

Anatomic Considerations

The most remarkable feature of the autonomic nervous system (also called the visceral, vegetative, or involuntary nervous system) is that a major part of it is located outside the brain and spinal cord, in proximity to the visceral structures that it innervates. This position alone seems to symbolize its relative independence from the cerebrospinal system. Also, in distinction from the somatic neuromuscular system, where a single motor neuron bridges the gap between the central nervous system (CNS) and the effector organ, in the autonomic ...

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