15_Nervous_Systems

15_Nervous_Systems - Nervous Systems Home Page 2006: D....

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1 Nervous Systems Home Page © 2006: D. Julian What are neurons? • Neurons transmit information quickly and accurately to specific locations in the body, thereby allowing rapid and precise coordination. • The membranes of most neurons are electrically excitable . • Neurons communicate information using a combination of electrical and chemical signals. • Neurons, together with special supporting cells, called glia , make up the nervous system . © 2006: D. Julian Diversity in nervous systems © 2006: D. Julian Campbel and Reece, Fig. 48.2
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2 Overview of the vertebrate nervous system Sensory neurons Motor neurons Interneurons © 2006: D. Julian Campbel and Reece, Fig. 48.3 knee-jerk reflex (a spinal reflex) Fast, “primitive” reflexes that form an arc in the spinal cord. The hammer stretches the quadriceps, which stretches sensors that stimulates a reflex contraction, returning the muscle to its initial size. © 2006: D. Julian Campbel and Reece, Fig. 48.4 Structure of a vertebrate neuron Campbel and Reece, Fig. 48.5 A typical neuron has a cell body, dendrites and an axon. In some nerves, myelination speeds propagation along the axon. © 2006: D. Julian Signals first enter through the dendritic processes, and are then “integrated” in the cell body and transmitted through the axon.
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3 Diversity of neurons Campbel and Reece, Fig. 48.5 © 2006: D. Julian Resting Potential and Action Potentials © 2006: D. Julian The resting membrane potential All cells at rest maintain transmembrane voltage that is negative on the inside with respect to the outside. © 2006: D. Julian Campbel and Reece, Fig. 48.9
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4 The theoretical starting point Let’s begin with an impermeable membrane separating the intracellular (high K + ) and extracellular (high Na + ) fluids. K INSIDE OUTSIDE Na Na Na Na Na Na K K K K K K Na A Cl A A A A A A Cl Cl Cl Cl Cl Cl ( + ) ( - ) © 2006: D. Julian A A Na Na ( + ) ( - ) Na Na Na Cl Cl Cl Cl Cl Na Cl K K K K K A A A K A Adding a K + channel Large “outward” concentration gradient causes net K + flux out of cell, making the inside negative, relative to the outside. K
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This note was uploaded on 04/12/2008 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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15_Nervous_Systems - Nervous Systems Home Page 2006: D....

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