25 000 genes encode proteins that control 100billion nerve cells that make 100 trillion connections Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings http www youtube com watch v JB7jSFeVz1U feature plcp Structural Classification of the Nervous System Central nervous system CNS Brain Spinal cord Neurons Neuroglia Peripheral nervous system PNS Nerves outside the brain and spinal cord Spinal nerves Cranial nerves Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous System Anatomy Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Functional Classification of the Peripheral Nervous System Sensory afferent division Nerve fibers that carry information to the central nervous system Motor efferent division Nerve fibers that carry impulses away from the central nervous system Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Functional Classification of the Peripheral Nervous System Motor efferent division continued Two subdivisions Somatic nervous system voluntary Autonomic nervous system involuntary Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Functions of the Nervous System Sensory input gathering information To monitor changes occurring inside and outside the body Changes stimuli Integration To process and interpret sensory input and decide if action is needed Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Functions of the Nervous System Motor output A response to integrated stimuli The response activates muscles or glands Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells Support cells in the CNS are grouped together as neuroglia Function to support insulate and protect neurons Each bead like structure that is strung along an axon is a single oligodendrocyte Microglia process harmful bacteria and act as the brain s immune cells Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings CNS Neuroglia Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells Astrocytes Abundant star shaped cells Brace neurons Form barrier between capillaries and neurons Control the chemical environment of the brain Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 3a Nervous Tissue Support Cells Microglia Spiderlike phagocytes Dispose of debris including dead brain cells and bacteria Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 3b Nervous Tissue Support Cells Ependymal cells Line cavities of the brain and spinal cord Circulate cerebrospinal fluid via beating cilia Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 3c Nervous Tissue Support Cells Oligodendrocytes Wrap around nerve fibers in the central nervous system Produce myelin sheaths Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Support Cells in PNS Satellite cells Schwann cells Protect neuron cell bodies Form myelin sheath in the peripheral nervous system Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Neurons nerve cells Cells specialized to transmit electrical messages Major regions of neurons Cell body nucleus and metabolic center of the cell Processes fibers that extend from the cell body Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Cell body Nissl substance Specialized rough endoplasmic reticulum Neurofibrils Intermediate cytoskeleton Maintains cell shape Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 4 Neuron Anatomy Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Cell body Nucleus Large nucleolus Processes outside the cell body Dendrites conduct impulses toward the cell body Axons conduct impulses away from the cell body Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Axons end in axonal terminals Axonal terminals contain vesicles with neurotransmitters Axonal terminals are separated from the next neuron by a gap Synaptic cleft gap between adjacent neurons Synapse junction between nerves Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Myelin sheath whitish fatty material covering axons roll like fashion the axon Schwann cells produce myelin sheaths in jelly Nodes of Ranvier gaps in myelin sheath along Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Nervous Tissue Neurons Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 5 Neuron Cell Body Location Most neuron cell bodies are found in the central nervous system Gray matter cell bodies and unmyelinated fibers Nuclei clusters of cell bodies within the white matter of the central nervous system Ganglia collections of cell bodies outside the central nervous system in PNS Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Neuron Classification Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 6 Functional Classification of Neurons Interneurons association neurons Found in neural pathways in the central nervous system Connect sensory and motor neurons Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Neurons Structural Classification Classified by number of cellular extensions Multipolar Bipolar Unipolar One axon several dendrites One axon and one dendrite Dendrite and axon fused into one process Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Structural Classification of Neurons Multipolar neurons many extensions from the cell body found in the brain and spinal cord Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings Figure 7 8a Structural Classification of Neurons Bipolar neurons one axon and one dendrite found in special sense regions Copyright 2009 Pearson Education Inc publishing as Benjamin Cummings