Download - Electrical Signals 1
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Electrical Signals 1
BIOL 1407
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Electrical Signals
• Changes in membrane potential currents
• Used by cells for quick communication
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Chemical vs. Electrical Signaling
• Type of Signals– Chemical – Electrical + Chemical = Electrochemical
• Types of Chemicals Used– Hormones– Neurotransmitters
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Chemical vs. Electrical Signaling
• Speed of Transmission– Slow– Fast
• Duration of Response– Long– Short
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Functions of Nervous Systems
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Neuron
• Cell body = Soma• Dendrites• Axon
– Axon Hillock– Axon Terminals =
Synaptic Knobs = Synaptic Terminals
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Types of Neurons
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Supporting Cells = Neuroglia
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Schwann Cells
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Neural Pathways Example
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Membrane Potential
• Electrical Difference = Potential• Membrane at Rest = Resting Membrane Potential (RMP)
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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
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• Chemically-Regulated Channels
• Gated• On dendrites and cell
body• Responds to
chemicals• Graded potentials
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• Voltage-Regulated Channels
• Gated• On axons• Respond to changes
in voltage• Action potentials
(APs)
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Voltage-Regulated Na+ ChannelNa+ Channel is Closed and Activated
Na+ Channel is Open; Stays Open for Short Amount of Time
Na+ Channel is Closed and Inactivated
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Voltage-Regulated K+ Channel
K+ Channel is Closed
K+ Channel is Open
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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
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Changes in Membrane Potentials
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Graded Potentials
• Occur at dendrites and cell bodies
• Response to changes in chemically-regulated channels
• Strength diminishes over distance
• Vary in strength
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Graded Potentials
• Can be depolarizing event or hyperpolarizing event
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Action Potentials
• Occur only along axons
• Strength is always the same
• Strength of signal stays the same along the entire length
• All-or-none
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Threshold Stimulus
• Threshold Stimulus – Enough depolarization to generate an AP – Usually -55 mV
• Subthreshold Stimulus – Insufficient depolarization to generate an AP
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The End
Unless otherwise specified, all images in this presentation came from:
Campbell, et al. Biology, 7th ed. and 8th ed. Pearson Benjamin Cummings.