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Saladin: Anatomy & Physiology: The Unity of Form and Function, Third

13. The Spinal Cord, Spinal Nerves, and Somatic Reflexes


© The McGraw-H Companies, 2003


Cross Section Spinal Cord Stretch

The Spinal Cord, Spinal Nerves, and Somatic Reflexes

Cross section through two fascicles (bundles) of nerve fibers in a nerve


The Spinal Cord 482

  • Functions 482
  • Gross Anatomy 482
  • Meninges of the Spinal Cord 482
  • Cross-Sectional Anatomy 485
  • Spinal Tracts 486

The Spinal Nerves 490

  • General Anatomy of Nerves and Ganglia 490
  • Spinal Nerves 492
  • Nerve Plexuses 494
  • Cutaneous Innervation and Dermatomes 503

Somatic Reflexes 503

  • The Nature of Reflexes 503
  • The Muscle Spindle 504
  • The Stretch Reflex 504
  • The Flexor (Withdrawal) Reflex 506
  • The Crossed Extensor Reflex 507
  • The Golgi Tendon Reflex 508

Chapter Review 510


  1. 1 Clinical Application: Spina Bifida 484
  2. 2 Clinical Application: Poliomyelitis and Amyotrophic Lateral Sclerosis 490
  3. 3 Clinical Application: Shingles 493
  4. 4 Clinical Application: Spinal Nerve Injuries 494
  5. 5 Clinical Application: Spinal Cord Trauma 508

Brushing Up

To understand this chapter, it is important that you understand or brush up on the following concepts:

  • Function of antagonistic muscles (p. 329)
  • Parallel after-discharge circuits (p. 472)

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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