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 “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.