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chap09outline - Chapter 9 Nervous System 9.1 Introduction(p...

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Chapter 9 - Nervous System 9.1 Introduction (p. 215; Fig. 9.1) A. The nervous system is composed of neurons and neuroglia. 1. Neurons transmit nerve impulses along nerve fibers to other neurons. 2. Nerves are made up of bundles of nerve fibers. 3. Neuroglia carry out a variety of functions to aid and protect components of the nervous system. B. Organs of the nervous system can be divided into the central nervous system (CNS), made up of the brain and spinal cord, and the peripheral nervous system (PNS), made up of peripheral nerves that connect the CNS to the rest of the body. C. The nervous system provides sensory, integrative, and motor functions to the body. 9.2 General Functions of the Nervous System (p. 215) A. Sensory receptors at the ends of peripheral nerves gather information and convert it into nerve impulses. B. When sensory impulses are integrated in the brain as perceptions, this is the integrative function of the nervous system. C. Conscious or subconscious decisions follow, leading to motor functions via effectors. 9.3 Neuron Structure (p. 216; Figs. 9.2-9.3) A. A neuron has a cell body with mitochondria, lysosomes, a Golgi apparatus, Nissl bodies containing rough endoplasmic reticulum, and neurofibrils. B. Nerve fibers include a solitary axon and numerous dendrites. 1. Branching dendrites carry impulses from other neurons (or from receptors) toward the cell body. 2. The axon transmits the impulse away from the axonal hillock of the cell body and may give off side branches. 3. Larger axons are enclosed by sheaths of myelin provided by Schwann cells and are myelinated fibers. a. The outer layer of myelin is surrounded by a neurilemma (neurilemmal sheath) made up of the cytoplasm and nuclei of the Schwann cell. b. Narrow gaps in the myelin sheath between Schwann cells are called nodes of Ranvier. 4. The smallest axons lack a myelin sheath and are unmyelinated fibers. 5. White matter in the CNS is due to myelin sheaths in this area. 6. Unmyelinated nerve tissue in the CNS appears gray. 9.4 Types of Neurons and Neuroglial Cells (p. 218) A. Neurons can be grouped in two ways: on the basis of structural differences (bipolar, unipolar, and multipolar neurons), and by functional differences (sensory neurons, interneurons, and motor neurons). B. Classification of Neurons (p. 218; Fig. 9.4) 1. Bipolar neurons are found in the eyes, nose, and ears, and have a single axon and a single dendrite extending from opposite sides of the cell body. 2. Unipolar neurons are found in ganglia outside the CNS and have an axon and a dendrite arising from a single short fiber extending from the cell body. 3. Multipolar neurons have many nerve fibers arising from their cell bodies and are commonly found in the brain and spinal cord. 4. Sensory neurons (afferent neurons) conduct impulses from peripheral receptors
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