Anatomy of the Peripheral Nervous System

The peripheral nervous system consists of those structures containing nerve fibers or axons that connect the CNS to motor, sensory, somatic and visceral end organs. This includes the cranial nerves (III-XII), spinal nerves, cervical, brachial and lumbosacral plexus and nerves of the extremity. These nerves are mostly mixed nerves (motor and sensory). In the peripheral nervous system, excluding the cranial nerves, they have their origin as a spinal nerve that is formed by the union of ventral and dorsal roots. The ventral root is largely formed by efferent fibers that innervate somatic musculature, but also contain some pre-ganglionic autonomic fibers that innervate blood vessels, smooth muscle and glandular epithelium. The dorsal root contains most of the afferent fibers from the somatic and visceral system. These spinal nerves then emerge from the neural foramina in the vertebral column and form extensive plexuses in which radical re-grouping of fibers occurs. Each of the peripheral nerves arising from these plexuses contains fibers contributed by two, three, four or even five ventral rami. As a result, the cutaneous areas supplied by the peripheral nerves do not correspond to the cutaneous area supplied by the individual dorsal roots. Similarly, several ventral roots may contribute fibers to a single muscle and conversely several muscles may receive fibers from a single ventral root.

The integral component of the neural connection between the CNS and motor, sensory, somatic and visceral end organs is the axon, which is the "cable" that makes the connection possible (Fig. 32.1). Axons may be surrounded by a myelin sheath (myelinated) or not (un-myelinated) and are surrounded by a fine connective tissue layer called the endoneurium.

Peripheral Neuropathy Natural Treatment Options

Peripheral Neuropathy Natural Treatment Options

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