In Chapters 3 and 4 the idea of the functional organization of the “final autonomic pathways” that transmit the central information to the peripheral targets was described. This idea sets the limits for the ensuing discussion of transmission of impulses along the final autonomic pathways (i.e., in the autonomic ganglia and to the target cells) as it occurs in vivo. In this section I want to emphasize that the centrally generated signals are faithfully transmitted from the preganglionic neurons through autonomic ganglia to the postganglionic neurons and from the postganglionic axons to the effector cells at the neuroeffector junctions. I will describe the principles of this signal transmission and how it can be modulated by peripheral reflexes and humoral mechanisms. I will not, however, extensively discuss the details of synaptic transmission in autonomic pathways including the different types of receptors for the neurotransmitters, their pharmacology and postreceptor pathways and chemical neuroanatomy (see articles in Burnstock and Hoyle [1992]; Elfvin et al. [1993]; McLachlan [1995]; Skok [2002]).