Lec14 - Neurobiology IV - Lecture 14 Nervous System IV...

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Lecture 14 Nervous System IV Reading: Chapter 4, pp. 161 – 165, 169 - 189 Lecture Outline Speed of propagation of neural impulse Types of Synapse Chemical Synapse Neurotransmitters
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Speed Of Propagation of Neural Impulse Diversity in Voltage Gated Ion Channels. Voltage gated Ca++ channels may also be involved.
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The speed depends upon the anatomy of the axon. Two characteristics are important: 1. Diameter of axons 2. Insulation
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1. Diameter of axons: larger diameter = decreased resistance = greater speed. e.g., Giant axons of squid – rapid escape. 2. Insulation: Presence of myelin sheath – phospholipids - produced by glial cells provides insulation to axons.
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Myelinated Axon diameter ~ 18.5 μ m Conduction Velocity ~ 42 m/s -1 Myelinated Unmyelinated Axon diameter ~ 2.5 μ m Conduction Velocity ~ 0.4 – 0.5 m/s -1 Axon diameter ~ 3.0 μ m Conduction Velocity ~ 4.2 m/s -1
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How Are Signals Transferred?
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Signal is transferred…. . from neuron (axon) to neuron (dendrite) or from neuron (axon) to target cell
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The transfer of signal could be through: 1. Electrical Synapse 2. Chemical Synapse
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1. Electrical Synapse: AP travels directly from the presynaptic to the postsynaptic cells via gap junctions without delay and without loss of signal strength. Gap junctions: Cytoplasmic channels between adjacent cells surrounded by special membrane proteins – Connexin allow entry of small molecules and ions. Examples: Giant axons of
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This note was uploaded on 09/12/2010 for the course BIOLOGY 225 taught by Professor Pavgi during the Winter '10 term at University of Michigan.

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Lec14 - Neurobiology IV - Lecture 14 Nervous System IV...

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