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These cells are the structural and functional units of the nervous system and are specialized to react to physical and chemical changes in their surroundings (p. 203).


These extensions of a neuron send information in the form of nerve impulses (p. 203).


These extensions of a neuron receive electrochemical messages (p. 203).


These consist of bundles of axons (p. 203).

neuroglial cells

These cells provide physical support, insulation, and nutrients for neurons (p. 203).

central nervous system

This system consists of the brain and spinal cord (p. 203).

peripheral nervous system

This system is composed of nerves that connect the central nervous system to other body parts (p. 203).

sensory receptors

Found at the end of peripheral neurons, these make possible the sensory function of the nervous system (p. 204).


These responsive structures, which are outside the nervous system, include muscles that contract and glands that secrete when simulated by nerve impulses (p. 204).

somatic nervous system

This part of the peripheral nervous system is under conscious control, and directs skeletal muscle (p. 205).

autonomic nervous system

This part of the peripheral nervous system controls effectors that are involuntary, such as the heart, smooth muscle in blood vessels, and various glands (p. 205).


This fatty lipoprotein forms a sheathlike covering around some axons (p. 205).

microglial cells

Scattered throughout the central nervous system, these cells support neurons and phagocytize bacterial cells and cellular debris (p. 205).


These cells align along nerve fibers and provide a myelin sheath around axons within the brain and spinal cord (p. 205).


Commonly found between neurons and blood vessels, provide structural support, join parts by their abundant cellular processes, and help regulate the concentrations of nutrients and ions within the tissue. These cells also form scar tissue that fills spaces following injury to the CNS (p. 205).

ependymal cells

Form an epithelial-like membrane that covers specialized brain parts (choroid plexuses) and forms the inner linings that enclose spaces within the brain (ventricles) and spinal cord (central canal) (p. 206).

schwann cells

These cells wind tightly around certain axons within the PNS, coating them with many layers of cell membrane that have a high proportion of myelin, thus forming a myelin sheath. The portion containing most of the cytoplasm and nuclei form the neurilemma (p. 206).


This surrounds the myelin sheath of axons within the PNS and consists of the portions of the Schwann cells that have most of the cytoplasm and nuclei; when peripheral nerves are damaged, this structure plays an important role in helping the axons to regenerate (p. 206).

nodes of Ranvier

The gaps between the Schwann cells. Action potentials can 'jump' from one gap to another, thus increasing the speed of conduction (saltatory conduction) (p. 206, 207, 213).

multipolar neurons

These neurons have many processes arising from their cell bodies. Only one process of each neuron is an axon; the rest are dendrites. Most neurons whose whose cell bodies lie within the brain or spinal cord are of this type (p. 208).

bipolar neurons

These neurons have only two processes, one arising from each end of the cell body, with one being an axon and the other a dendrite. These neurons are found within specialized parts of the eyes, nose, and ears (p. 208).

unipolar neurons

These neurons have a single process extending from the cell body, which divides into two branches, which really function as a single axon. One branch is associated with dendrites near a peripheral body part while the other enters the brain or spinal cord (p. 208).


The cell bodies of some unipolar neurons aggregate in specialized masses of nervous tissue, which are located outside the brain and spinal cord (p. 208).

sensory neurons

These afferent neurons carry nerve impulses from peripheral body parts into the brain or spinal cord (p. 208).


These multipolar neurons lie entirely within the brain or spinal cord and transmit impulses from one part of the brain or spinal cord to another; also known as association neurons (p. 209).


The cell bodies of some interneurons aggregate in specialized masses of nervous tissue that are similar to ganglia, but which are located within the central nervous system (p. 209).

motor neurons

These efferent multipolar neurons carry nerve impulses out of the brain or spinal cord to effectors, stimulating muscles to contract or glands to secrete (p. 209).

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