Evolution of the Cardiovascular Autonomic Nervous System in Vertebrates

Publisher Summary This chapter discusses the evolution of the cardiovascular autonomic nervous system (ANS) in vertebrates and comparative aspects of the autonomic regulation of the cardiovascular system. Many of the basic functions of the ANS were originally discovered in ectothermic vertebrates. Within hagfishes and lampreys the ANS is considered rudimentary, because either some organs are devoid of innervation or most organs lack dual innervation. Therefore, while the ANS of early vertebrates can be considered simple in comparison to subsequent groups of vertebrates, the basic foundations of the ANS were established by the time of fishes and evolved prior to the invasion of terrestrial habitats. The morphology and the function of the heart and cardiovascular systems of vertebrates have undergone large evolutionary changes associated with the transition between water and air-breathing and during the evolution of endothermy within mammals and birds. In tunicates and Amphioxus, the endothelium within the blood vessel is either very poorly developed or absent, and there is no endothelium in innervation amongst protostomes.