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CHAPTER 11 Fundamentals of the Nervous System and Nervous Tissue Part A LEARNING OBJECTIVES At the end of the discussion students should be able to : • Explain the Organization of Nervous system • Define and enlist the histological structures of Nervous Tissue. • Recognize and compare the structural and functional classification of Neurons • Explain the developmental aspects of Neurons LECTURE OUTLINE Organization of the Nervous System Histology of Nervous Tissue 1. 2. 3. 4. Neuron Neuroglia cells Structural Classification of Neurons Functional Classification of Neurons Grey mater and white mater Developmental Aspects of Neurons Before starting lets have a look on the basic function of nervous system. Copyright © 2010 Pearson Education, Inc. The Nervous System The nervous system is the master controlling and communicating system of the body. Nervous system has three overlapping systems. 1. Sensory input 2. Integration 3. Motor output Copyright © 2010 Pearson Education, Inc. Sensory input Integration Motor output Copyright © 2010 Pearson Education, Inc. Figure 11.1 Organization of the Nervous System 1. Central nervous system (CNS) • Brain and spinal cord • Integration and command center Copyright © 2010 Pearson Education, Inc. Organization of the Nervous System 2. Peripheral nervous system (PNS) • Paired spinal and cranial nerves carry messages to and from the CNS Copyright © 2010 Pearson Education, Inc. Organization of the Nervous System Peripheral nervous system 1. Sensory (afferent) division 2. Motor (efferent) division Copyright © 2010 Pearson Education, Inc. Organization of the Nervous System Motor division of PNS 1. Somatic (voluntary) nervous system 2. Autonomic (involuntary) nervous system (ANS) Copyright © 2010 Pearson Education, Inc. • Somatic (Conscious control of skeletal muscles) • Autonomic (Regulates smooth muscle, cardiac muscle, and glands) Copyright © 2010 Pearson Education, Inc. Autonomic Two functional subdivisions Sympathetic Copyright © 2010 Pearson Education, Inc. Parasympathetic Confused Copyright © 2010 Pearson Education, Inc. Don’t worry we will do it together Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Before going to next slide just revise What is histology????? Copyright © 2010 Pearson Education, Inc. Histology of Nervous Tissue Two principal cell types 1. Neurons (excitable cells that transmit electrical signals) 2. Neuroglia cells Copyright © 2010 Pearson Education, Inc. A. Neuron Excitable cells of the nervous system having two types of processes. 1. Dendrites 2. Axons Copyright © 2010 Pearson Education, Inc. Bundles of processes are called • Tracts in the CNS • Nerves in the PNS Copyright © 2010 Pearson Education, Inc. Dendrites (receptive regions) Cell body (biosynthetic center and receptive region) NEURON Axon Nucleus Axon hillock (b) Copyright © 2010 Pearson Education, Inc. Schwann cell (one internode) Axon terminals (secretory region) Figure 11.4b NEURON Dendrites 1. Impulse Receiving processes 2. Projects out from cell body of the neuron Copyright © 2010 Pearson Education, Inc. NEURON Axon 1. One axon per cell arising from the axon hillock 2. Impulse sending processes 3. Long axons (nerve fibers) Copyright © 2010 Pearson Education, Inc. NEURON Structural Classification of Neurons Multipolar—1 axon and several dendrites • Most abundant • Motor neurons and interneurons Bipolar—1 axon and 1 dendrite • Rare, e.g., retinal neurons Unipolar (pseudounipolar) Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Table 11.1 (2 of 3) NEURON Functional Classification of Neurons 1. Sensory (afferent) Transmit impulses from sensory receptors toward the CNS 2. Motor (efferent) Carry impulses from the CNS to effectors 3. Interneurons most are entirely within the CNS Copyright © 2010 Pearson Education, Inc. B. NEUROGLIA CELLS (supporting cells) 1. Astrocytes (CNS) 2. Microglia (CNS) 3. Ependymal cells (CNS) 4. Oligodendrocytes (CNS) 5. Satellite cells (PNS) 6. Schwann cells (PNS) Copyright © 2010 Pearson Education, Inc. Astrocytes • Most abundant, versatile, and highly branched glial cells Copyright © 2010 Pearson Education, Inc. Microglia • Small, ovoid cells with thorny processes • Migrate toward injured neurons Copyright © 2010 Pearson Education, Inc. Ependymal Cells • Range in shape from squamous to columnar • May be ciliated • Line the central cavities of the brain and spinal column Copyright © 2010 Pearson Education, Inc. Oligodendrocytes • Branched cells • Processes wrap CNS nerve fibers, forming insulating myelin sheaths Copyright © 2010 Pearson Education, Inc. White Matter and Gray Matter White matter • Dense collections of myelinated fibers Gray matter • Mostly neuron cell bodies and unmyelinated fibers Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Table 11.1 (3 of 3) Developmental Aspects of Neurons • The nervous system originates from the neural tube and neural crest formed from ectoderm • The neural tube becomes the CNS • Neuroepithelial cells of the neural tube undergo differentiation to form cells needed for development • Neuroblasts sprout axons to connect with targets and become neurons Copyright © 2010 Pearson Education, Inc. WOW WE DID IT Copyright © 2010 Pearson Education, Inc. BUT BEFORE GOING WE HAVE TO SUMMARIZE IT. Copyright © 2010 Pearson Education, Inc. KEYPOINTS Organization of the nervous system 1. Central nervous system 2. Peripheral nervous system a. Sensory division b. Motor division - Somatic nervous system - Autonomic nervous system Copyright © 2010 Pearson Education, Inc. KEYPOINTS Histology of nervous Tissue • Neurons Dendrites Axons Classification • Neuroglia cells • Gray matter & white matter Copyright © 2010 Pearson Education, Inc. KEYPOINTS Neuroglia cells • Astrocytes (CNS) • Microglia (CNS) • Ependymal cells (CNS) • Oligodendrocytes (CNS) • Satellite cells (PNS) • Schwann cells (PNS) Copyright © 2010 Pearson Education, Inc. Developmental Aspects of Neurons The nervous system originates from the neural tube and neural crest formed from ectoderm Copyright © 2010 Pearson Education, Inc. FINALLY WE FINISHED FOR TODAY ANY QUESTIONS???? Copyright © 2010 Pearson Education, Inc.