Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

©2018 Achieve Test Prep Page 169 of 367 14.8 Chapter Fourteen Review The brain and spinal cord make up the central nervous system, and the cranial nerves and spinal nerves constitute the peripheral nervous system: • The CNS consists of the brain and spinal cord; the remainder of the nervous tissue forms the PNS. The spinal cord is encompassed by three meninges and conveys sensory and motor information: • The adult spinal cord includes two localized enlargements, which provide innervation to the limbs. The spinal cord has 31 segments, each associated with a pair of dorsal roots and a pair of ventral roots. • The filum terminale (a strand of fibrous tissue), which originates at the conus medullaris becomes a branch of the coccygeal ligament. • Spinal nerves are mixed nerves: they contain both afferent (sensory) and efferent (motor) fibers. • The spinal meninges provide physical stability and shock absorption for neural tissues of the spinal cord; the cranial meninges surround the brain. • The dura mater conceals the spinal cord; inferiorly, it tapers into the coccygeal ligament. The epidural space divides the dura mater from the walls of the vertebral canal. • Interior to the inner surface of the dura mater is the subdural space, the arachnoid mater (the second meningeal layer), and the subarachnoid space. The subarachnoid space includes cerebrospinal fluid (CSF), which acts as a shock absorber and a diffusion channel for dissolved gases, nutrients, chemical messengers, and waste products. • The pia mater, a meshwork of elastic and collagen fibers, is the innermost meningeal layer. Denticulate ligaments extend from the pia mater to the dura mater. Gray matter is the area of integration and command initiation, and white matter carries information from place to place: • The white matter of the spinal cord includes myelinated and unmyelinated axons, whereas the gray matter includes cell bodies of neurons and neuroglia and unmyelinated axons. The projections of gray matter toward the outer surface of the cord are called horns. • The posterior gray horns contain somatic and visceral sensory nuclei; nuclei in the anterior gray horns function in somatic motor control. The lateral gray horns contain visceral motor neurons. The gray commissures contain axons that cross from one side of the spinal cord to the other. • The white matter can be divided into six columns (funiculi), each of which contains tracts (fasciculi). Ascending tracts relay information from the spinal cord to the brain, and descending tracts carry information from the brain to the spinal cord.