In the interaction of emotion and physiology, two important conceptualizations can be distinguished: efferent and afferent effects of the autonomic nervous system (ANS) in emotion. Although the afferent and efferent definitions of emotional response are not mutually exclusive, the large majority of research on emotion has been based on the efferent conceptualization. This chapter draws on research findings in support of each conceptualization. It first considers the anatomy and central control of the ANS. The anatomical structure of the ANS and its central control constitute the basis for understanding autonomic effects of emotion. The chapter talks about neural feedback mechanisms, although hormonal, chemical, and physical feedback mechanisms may also operate through interactions with central components of this neural pathway. Various neural feedback mechanisms exist that allow for the transmission of information on homeostatic parameters. The exact nature and role of peripheral physiological responses to emotional feelings remain to be determined.