Medical Terminology

12 Nervous System Learning Objectives Upon completion of this chapter, you will be able to: ■ Identify and define the combining forms and suffixes introduced in this chapter. ■ Correctly spell and pronounce medical terms and major anatomical structures relating to the nervous system. ■ Locate and describe the major organs of the nervous system and their functions. ■ Describe the components of a neuron. ■ Distinguish between the central nervous system, peripheral nervous system, and autonomic nervous system. ■ Build and define nervous system medical terms from word parts. ■ Identify and define nervous system vocabulary terms. ■ Identify and define selected nervous system pathology terms. ■ Identify and define selected nervous system diagnostic procedures. ■ Identify and define selected nervous system therapeutic procedures. ■ Identify and define selected medications relating to the nervous system. ■ Define selected abbreviations associated with the nervous system.

Nervous System at a Glance Function The nervous system coordinates and controls body function. It receives sensory input, makes decisions, and then orders body responses. Organs brain nerves spinal cord Combining Forms cephal/o head cerebell/o cerebellum cerebr/o cerebrum encephal/o brain gli/o glue medull/o medulla oblongata mening/o meninges meningi/o meninges myel/o spinal cord neur/o nerve phas/o speech poli/o gray matter pont/o pons radicul/o nerve root thalam/o thalamus thec/o sheath (meninges) ventricul/o brain ventricle Suffixes pain, sensitivity feeling, sensation -algesia weakness -esthesia speech -paresis paralysis -phasia muscle coordination -plegia -taxia388

Nervous System Illustrated brain, p. 392 spinal cord, p. 394Coordinates body functions Transmits messages to and from the brainnerves, p. 395 Spinal nerves BrainTransmits messages to and of the from the central nervous Central system peripheral nervous nervous system system Spinal cord

390 Chapter 12 Anatomy and Physiology of the Nervous System brain nerves central nervous system peripheral nervous system (per-IF-er-al) cranial nerves (KRAY-nee-al) sensory receptors glands spinal cord muscles spinal nervesMed Term Tip The nervous system is responsible for coordinating all the activity of the body. To do this, it first receives information from both external and internal sensory re-Neuroglial tissue received its name ceptors and then uses that information to adjust the activity of muscles and glandsas a result of its function. This tis- to match the needs of the body.sue holds neurons together. There-fore, it was called neuroglial, a term The nervous system can be subdivided into the central nervous system (CNS) and theliterally meaning “nerve glue.” peripheral nervous system (PNS). The central nervous system consists of the brain and spinal cord. Sensory information comes into the central nervous system, where it is processed. Motor messages then exit the central nervous system carrying com- mands to muscles and glands. The nerves of the peripheral nervous system are cranial nerves and spinal nerves. Sensory nerves carry information to the central nervous sys- tem, and motor nerves carry commands away from the central nervous system. All portions of the nervous system are composed of nervous tissue. Nervous Tissue axon (AK-son) neuron (NOO-ron) dendrites (DEN-drights) neurotransmitter (noo-roh-TRANS-mit-ter) myelin (MY-eh-lin) synapse (sih-NAPSE) nerve cell body synaptic cleft (sih-NAP-tik) neuroglial cells (noo-ROH-glee-all) Nervous tissue consists of two basic types of cells: neurons and neuroglial cells. Neu- rons are individual nerve cells. These are the cells that are capable of conducting electrical impulses in response to a stimulus. Neurons have three basic parts: dendrites, a nerve cell body, and an axon (see Figure 12.1A ■). Dendrites are highly branched projections that receive impulses. The nerve cell body contains the nu- cleus and many of the other organelles of the cell (see Figure 12.1B ■). A neuron has only a single axon, a projection from the nerve cell body that conducts the elec- trical impulse toward its destination. The point at which the axon of one neuron meets the dendrite of the next neuron is called a synapse. Electrical impulses can- not pass directly across the gap between two neurons, called the synaptic cleft. They instead require the help of a chemical messenger, called a neurotransmitter. A variety of neuroglial cells are found in nervous tissue. Each has a different support function for the neurons. For example, some neuroglial cells produce myelin, a fatty substance that acts as insulation for many axons so that they con- duct electrical impulses faster. Neuroglial cells do not conduct electrical impulses. Central Nervous System gray matter tract meninges (men-IN-jeez) white matter myelinated (MY-eh-lih-nayt-ed) Because the central nervous system is a combination of the brain and spinal cord, it is able to receive impulses from all over the body, process this informa-