Canine Autonomic Nervous System

(NOTE: Pathway sections are completed; physiology sections are still under development.)

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 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 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 organ function. In this web site, visceral reflexes are included under Physiololgical Features.

3] ANS refers to visceral peripheral innervation and reflexes plus selected brain components that influence viscera, such as hypothalamus. Brain control of visceral organs is less thoroughly understood than peripheral innervation of viscera. It is presented only superficially in this web site.

General ANS Features: an introduction to the Autonomic Nervous System (ANS):
two-neuron VE pathways; sympathetic & parasympathetic divisions; enteric innervation.

Sympathetic Division: presents the thoracolumbar division of the ANS and turorials
for learning sympathetic VE pathways to six body regions: head, neck, thorax, abdomen, etc.

Parasympathetic Division: presents the craniosacral division of the ANS and turorials
for learning parasympathetic VE pathways to the head, thorax, abdomen, and pelvis.

Trace Pathways: provides opportunities to demonstrate knowledge of ANS pathways by revealing VE pathways to target organs and by taking animated quizes to construct pathways.

Physiological Features: highlights ANS function in three contexts: molecular aspects
of visceral innervation, neural control of visceral organs, and central nervous system involvement.

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