This canine Autonomic Nervous System tutorial focuses on visceral efferent pathways that innervate smooth muscle, cardiac muscle, and gland tissue in the dog. An overview of physiological and pharmacological aspects of Autonomic Nervous System operation are also included. Web site information can be accessed via the above navigation bar (click to view a topic).
NOTE: The term "autonomic" means self-rule/self-govern [from the Greek: auto = self; nomos = rule]. The name implies that visceral innervation operates involuntarily on its own (in contrast to the voluntary control characteristic of somatic innervation of skeletal muscle). Visceral organs generally operate below conscious control, even though one can initiate/inhibit some visceral activities (e.g., urination, defecation) and indirectly influence others (e.g., heart rate).
The phrase Autonomic Nervous System (ANS) can be used in three contexts:
1] ANS refers to Visceral Efferent (VE) innervation of viscera, i.e., the two-neuron peripheral pathway from the Central Nervous System (CNS) to visceral organs. This is the original anatomical definition and it is a major focus of this web site, i.e., identifying VE pathways to viscera located in different regions of the body.
2] ANS refers to General Visceral Afferent (GVA) as well as Visceral Efferent (VE) peripheral innervation of viscera and to visceral relexes. Visceral efferent and afferent axons both use the same peripheral nerve pathways, and both are necessary for visceral reflexes.
3] ANS refers to visceral peripheral innervation plus selected brain components that regulate visceral activity. To view CNS components associated with the ANS (in a separate page) click here: CNS Visceral Control Summary.