Second Level: The Brainstem

Abstract

The sympathetic and parasympathetic divisions of the ANS are integrated and regulated by a hierarchy of central structures. This central autonomic neural net-work has been identified and mapped in recent years and functional neuroimag-ing data largely support it. Such a network involves reciprocal connections, both direct and indirect, between the two efferent systems and with more cranial neu-ral clusters located in the brainstem, hypothalamus, limbic system, and the insu-lar cortex. As examples of that organization, this Chapter discusses the neural mechanisms that control arterial blood pressure, heart rate, breathing, immunity, and gastrointestinal function and how they vary in the three body configurations (wakefulness, NREM sleep, REM sleep).