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Made up of neurons and neuroglia cells Anatomical subdivisions of NS Functional Overview of NS CNS Integration, processing and coordination of sensory data and motor commands Higher functions PNS 1. Sensory or afferent division with sensory neurons. Brings sensory info to CNS. Begins as receptors, ends in? 2. Motor or efferent division with motor neurons. Brings motor commands to peripheral tissue. Ends at effector cells. Peripheral Nervous System Cellular Organization of Neural Tissue Two cell types: 1. Neurons 2. Neuroglia Schwann cells Satellite cells Astrocytes Oligodendrocytes Microglial cells Ependymal cells See fig. 13-5 Compare to fig. 14-4 General Neuron Structure Cell body or Soma with Perikaryon Dendrites Axon with axon hillock Synaptic terminals Astrocytes: largest & most numerous Function: BBB structural framework & repairs regulation of ions, nutrients, gases Oligodendrocyte Smaller than astrocyte Produce myelin in CNS (white matter vs. gray matter!) Myelin = ? Microglia cells Smallest Phagocytosis of ? # during infection or injury Ependymal cells Lining of ventricles & central canal Some regions ciliated Some specialized to produce CSF Schwann Cells and Peripheral Axons Responsible for myelination, but surround all peripheral axons! Involved in repair mechanism after injury Wallerian Degeneration myelinated Structural Neuron Classification Axon hillock Anaxonic In CNS Unipolar Also called pseudounipolar Sensory neurons See fig. 13-10 Structural Neuron Classification cont. . . Bipolar Unmyelinated Rare, but important in special senses Multipolar Most common All motor neurons Functional Neuron Classification 1) somatic vs. visceral sensory or afferent monitoring of ? 2) somatic vs. visceral motor or efferent carry instructions to ? 3) Inter- or association neurons Synapse Site of communication between two nerve cells or nerve cell and effector cell neuro-effector junctions (example?) Electrical vs. chemical synapses Chemical Synapse vs. Electrical Synapse Space between two cells Signal transduction via NT Most common Direct physical contact between cells = gap junctions Direct signal transduction Rare, but occurs in CNS and heart Chem. Synapse Structure 1. 2. 3. Axon terminal of presynaptic cell Synaptic cleft Dendrite or cell body of postsynaptic cell Neuron Organization Divergence - One neuron synapses with several, effectively "spreading the word". Convergence - Several neurons synapse with a single neuron, concentrating the input. Serial processing - step-wise, sequential Parallel processing - simultaneous processing of different information Anatomical Organizatin of NS Collections of cell bodies - ganglion in PNS, center or nucleus in CNS Bundles of axons - tracts in CNS, nerves in PNS “White” = myelinated axons, both nerves and tracts “Gray” = non-myelinated material, dendrites, synapses and cell bodies as well as nonmyelinated axons. In CNS – nucleus; in PNS - ganglia Compare to fig. 13-15