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Electrical Signals 1 BIOL 1407 Slide 2 Electrical Signals Changes in membrane potential currents Used by cells for quick communication Slide 3 Chemical vs. Electrical Signaling Type of Signals Chemical Electrical + Chemical = Electrochemical Types of Chemicals Used Hormones Neurotransmitters Slide 4 Chemical vs. Electrical Signaling Speed of Transmission Slow Fast Duration of Response Long Short Slide 5 Functions of Nervous Systems Slide 6 Neuron Cell body = Soma Dendrites Axon Axon Hillock Axon Terminals = Synaptic Knobs = Synaptic Terminals Slide 7 Slide 8 Types of Neurons Slide 9 Supporting Cells = Neuroglia Slide 10 Schwann Cells Slide 11 Slide 12 Neural Pathways Example Slide 13 Membrane Potential Electrical Difference = Potential Membrane at Rest = Resting Membrane Potential (RMP) Slide 14 Slide 15 Membrane Proteins Sodium Potassium Pump Maintains Resting Membrane Potential Leak Channels Na + and K + Leak Channels Chemically-Regulated (Gated) Channels Also called Ligand-Gated Channels Voltage-Regulated (Gated) Channels Na + and K + Voltage-Regulated Channels Slide 16 Slide 17 Slide 18 Chemically-Regulated Channels Gated On dendrites and cell body Responds to chemicals Graded potentials Slide 19 Voltage-Regulated Channels Gated On axons Respond to changes in voltage Action potentials (APs) Slide 20 Voltage-Regulated Na + Channel Na + Channel is Closed and Activated Na + Channel is Open; Stays Open for Short Amount of Time Na + Channel is Closed and Inactivated Slide 21 Voltage-Regulated K + Channel K + Channel is Closed K + Channel is Open Slide 22 Changes in Membrane Potential Resting Membrane Potential (RMP) Depolarization Membrane becomes more + than RMP Hyperpolarization Membrane becomes more than RMP Action Potential: pattern of MP changes Depolarization Repolarization Undershoot: Brief Hyperpolarization Slide 23 Changes in Membrane Potentials Slide 24 Graded Potentials Occur at dendrites and cell bodies Response to changes in chemically- regulated channels Strength diminishes over distance Vary in strength Slide 25 Graded Potentials Can be depolarizing event or hyperpolarizing event Slide 26 Action Potentials Occur only along axons Strength is always the same Strength of signal stays the same along the entire length All-or-none Slide 27 Slide 28 Threshold Stimulus Threshold Stimulus Enough depolarization to generate an AP Usually -55 mV Subthreshold Stimulus Insufficient depolarization to generate an AP Slide 29 Slide 30 The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. Biology, 7 th ed. and 8 th ed. Pearson Benjamin Cummings.