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Saladin: Anatomy & Physiology: The Unity of Form and Function, Third
© The McGraw-H Companies, 2003
The Spinal Cord, Spinal Nerves, and Somatic Reflexes
Cross section through two fascicles (bundles) of nerve fibers in a nerve
Chapter Review 510
Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text I © The McGraw-Hill
Physiology: The Unity of Nerves, and Somatic Companies, 2003
Form and Function, Third Reflexes Edition
482 Part Three Integration and Control
We studied the nervous system at a cellular level in chapter 12.
In these next two chapters, we move up the structural hierarchy to study the nervous system at the organ and system levels of organization. The spinal cord is an "information highway" between your brain and your trunk and limbs. It is about as thick as a finger, and extends through the vertebral canal as far as your first lumbar vertebra. At regular intervals, it gives off a pair of spinal nerves that receive sensory input from the skin, muscles, bones, joints, and viscera, and that issue motor commands back to muscle and gland cells. The spinal cord is a component of the central nervous system and the spinal nerves a component of the peripheral nervous system, but these central and peripheral components are so closely linked structurally and functionally that it is appropriate that we consider them together in this chapter. The brain and cranial nerves will be discussed in chapter 14.
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