PSIO 5th Edition Lecture 33 Outline of Last Lecture AUTONOMIC NERVOUS SYSYEM Outline of Current Lecture I Neurophysiology Resting Membrane Potential II Bioelectricity III Resting Membrane Potential IV Manipulation Current Lecture Objective 1 Describe the normal concentration and electrical gradients for Na and K that exist across the membrane of all cells 2 Predict what will happen to the membrane potential of a cell is the permeability of the membrane increases or decreases for Na of K 3 Compare and contract the characteristics of leak channels and voltage gated chemically gated and mechanically gated channels Neuronal Tissue Two Types of Cells A Nerve Cells Neurons Involved in the generation and interpretation of Electrical Signals B Glial Cells Neurolgia Support neuronal cell activity Bioelectricity Resting membrane potential Baseline electrical condition of ALL cells depends on 2 parameters A Transmembrane Ion Gradients Na and K B Membrane Permeabilty to those ions Action potential Resting Membrane Potential A negatively charged proteins and phosphate Ion Gradients Na K ATPase develops and maintains steady state ion gradients for ALL cells Permeability Intracellular cytoplasm Extracellular 1 Pumping creates ionic gradient for K 2 K leaks out down its concentration gradient so that the inside of the cells becomes more negative 3 Now two kinds of forces push pull on K Resting Membrane Potential 2 opposing forces Chemical and Electrical Chemical pushes K out and Electrical pulls K in Chemical and Elecrical forces for K are nearly in balance outwardly directed K gradient results in an inside negative electrical potential The Electrical potential difference PD is measured in Volts 0 05 volts to 0 1 volts K dominated inside negative membrane potential is a characteristic of ALL cells at rest Modulation of the membrane potential changes in the membrane permeability can produce large changes in the membrane potential Membrane permeability open channels to an ion K or Na for that ion Regulation of channel mediated ion permeability allows cells to generate electrical signals Keys to manipulation of Membrane Potential 1 Maintain stable Na and K gradients Na K ATPase 2 Vary the activity of specific ion channels Manipulation of membrane Permeability Ion Channels 1 Integral membrane proteins 2 Channels can be open or closed 3 Some channels are routinely open 4 Some channels have their open states regulated a Chemically ligand gated channels open when a signal molecule binds to the channel protein ACh b Mechanically gated channels open when membrane gets stretched c Voltage gated channels open when membrane potential gets less negative depolarized
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