9. Nervous System

9. Nervous System - Biology107Fall07 NervousSystem:Ch.48

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Biology 107 – Fall ‘07                              Nervous System:  Ch. 48 1 OVERVIEW OF NERVOUS SYSTEMS The nervous system has three overlapping functions: o Sensory input Sensory receptors Transduce stimuli: Change stimulus energy   change in membrane potential o Integration Central nervous system (CNS) and synapses o Motor output e.g. muscle contraction These functions involve both parts of the nervous system o Central nervous system (CNS) Brain and spinal cord o Peripheral nervous system (PNS)  – everything else Sensory nerves Motor nerves The nervous system is composed of neurons and supporting cells o Neurons  – fig. 48.5; 48.6 Dendrites Receive information from other neurons Axon hillock Action potentials are “born” here Axon Conducts action potentials to… Axon terminal Releases transmitter to post synaptic cell o Synapse  Fig. 48.17: functional  contact between axon terminal and  postsynaptic  cell. Presynaptic membrane Axon terminal membrane, with transmitter Synaptic cleft (gap) space Postsynaptic membrane Could be dendrites of another neuron; could be skeletal muscle o Neurotransmitters  – Table 48.1 FUNCTIONAL ORGANIZATION OF NEURONS AND SUPPORTING CELLS Three major classes of neurons o Sensory neurons :  Information from environment to CNS o Interneurons :  Neurons that synapse with other neurons. integration o Motor neurons:   Conduct signals (information ) from  CNS to effectors
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Biology 107 – Fall ‘07                              Nervous System:  Ch. 48 2 Clusters of neurons/cell bodies o Cortical “gray matter”   (due to presence of cell bodies and synapses) o Nucleus:   Cell bodies clustered in CNS o Ganglion:  Cell bodies clustered outside  CNS. Supporting cells – Fig. 48.7, .8 o Glia Astrocytes Blood brain barrier Oligodendrocytes Make CNS myelin Schwann cells Makes PNS myelin o Myelination  – Fig. 48.8 Myelin – fatty insulation surrounding axons Function: increase speed of conduction of signals (action potentials) THE NATURE OF NERVE SIGNALS All cells have an electrical voltage across their plasma membranes; =  membrane potential o Concentration gradients + selective membrane permeabilities influence membrane potential Ion Conc. inside cell Conc. outside cell Difference Na+ 15 mM 150 mM 10X outside K+ 150 mM 5 mM 30X inside Cl- 10 mM 120 mM 12X outside Anions  in cell 100 mM ---------
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This note was uploaded on 11/16/2011 for the course BIOL 107 taught by Professor Abbot during the Spring '08 term at UConn.

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9. Nervous System - Biology107Fall07 NervousSystem:Ch.48

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