The nervous system supplies efferent innervation to all organs via the motor system (see Chapter 5) or the ANS. In the motor system, there is an uninterrupted path from the cell body of the motor neuron, located in either the ventral horn of the spinal cord or a brainstem motor nucleus, to the skeletal muscle cells. In the ANS, the efferent path consists of a two-neuron chain with a synapse interposed between the CNS and the effector cells (Fig. 6.1). The cell bodies of the autonomic motor neurons are located in the spinal cord or specific brainstem nuclei. An efferent fiber emerges as the preganglionic axon and then synapses with neurons located in a peripheral ganglion. The neuron in the ganglion then projects a postganglionic axon to the autonomic effector cells.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.