Autonomic Nervous System
The autonomic nervous system and the role it plays in governing the behavior of the cardiovascular system are significant in both its complexity and importance for one’s quality of life. The hypothalamus is the brain center which governs all essential “ho
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Paul A. Iaizzo and Kevin Fitzgerald
Abstract
The autonomic nervous system and the role it plays in governing the behavior of the cardiovascular system are significant in both its complexity and importance for one’s quality of life. The hypothalamus is the brain center which governs all essential “homeostatic” functions of the human body; these integrative functions include control over the autonomic nervous system, various somatic pathways, and the body’s hormonal systems. The autonomic nervous system can be considered to have two subdivisions that are considered somewhat antagonistic but also function in a complementary nature; simultaneous changes within the parasympathetic and sympathetic branches of this system allow for rapid and essential changes in cardiac parameters such as heart rate, contractility, and/or stroke volume. Increased sympathetic outflow relative to normal resting conditions most often causes an excitatory response in physiologic parameters (such as increases in heart rate and/or smooth muscle contraction), whereas parasympathetic stimulation usually results in calming adjustments (lower heart rates, decreased contractility, and/or vasodilatation). Alterations of the cardiac and aortic baroreceptors, as well as the autonomic nerves that innervate the heart, are important to consider in many disease states. Keywords
Sympathetic anatomy • Parasympathetic anatomy • Baroreceptors • Homeostasis • Hypothalamic control • Effector pathways • Heart rate • Stroke volume • Contractility • Arteriolar pressure • Cardiac denervation
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Introduction
The autonomic nervous system coordinates the involuntary control of the viscera and other tissues throughout the body, with the primary exception of skeletal muscle. The hypothalamus is the brain center which governs all essential homeostatic functions of the human body; these integrative
P.A. Iaizzo, PhD (*) Department of Surgery, University of Minnesota, 420 Delaware St. SE, B172 Mayo, Minneapolis, MN 55455, USA e-mail: [email protected] K. Fitzgerald, MS Medtronic, Inc., Minneapolis, MN, USA
functions include control over the autonomic nervous system, various somatic pathways, and the body’s hormonal systems. Briefly, homeostasis can be defined as the control of the internal milieu, which in general is kept nearly constant within quite narrow limits, despite potential severe perturbations that human bodies can experience (e.g., extreme hot and cold temperatures). The hypothalamus is a small part of the brain considered as a neuronal continuum extending from the midbrain through to the basal regions of the telencephalon. Further, the lateral hypothalamus can be thought to be reciprocally connected with the upper brainstem and the limbic system (these are the brain centers which control emotions, learning, etc.). As such, it receives primary sensory inputs from afferents near the body surface and from internal structures via the ascending spinobulboreticular pathways.
© Springer International Publishing Switzerland 2015 P.A. Iaizzo (ed.), Handbook
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