ABSTRACT
Study objectives Explain how various regions of the central nervous system regulate autonomic nervous system function Explain how autonomic reexes contribute to homeostasis Describe how the neuroeffector junction in the autonomic nervous system differs from that of a neuron-to-neuron synapse Compare and contrast the anatomical features of the sympathetic and parasympathetic systems For each neurotransmitter in the autonomic nervous system, list the neurons that release them and the type and location of receptors that bind with them Describe the mechanisms by which neurotransmitters are removed Distinguish between cholinergic and adrenergic receptors Describe the overall and specic functions of the sympathetic system Describe the overall and specic functions of the parasympathetic system Explain how the effects of the catecholamines differ from those of direct sympathetic stimulation
. Introduction The autonomic nervous system (ANS) is also known as the visceral or involuntary nervous system. It functions without conscious, voluntary control. Because it innervates cardiac muscle, smooth muscle, and various endocrine and exocrine glands, this nervous system inuences the activity of most of the organ systems in the body. Therefore, it is evident that the ANS makes a signicant contribution to homeostasis. The regulation of blood pressure, gastrointestinal responses to food, contraction of the urinary bladder, focusing of the eyes, and thermoregulation are just a few of the many homeostatic functions regulated by the ANS. Several distinguishing features of the ANS and the somatic nervous system, which innervates skeletal muscle, are summarized in Table 9.1.
