KEY CONCEPT FIGURE 23.50 A circuit model of nerve-impulse propagation along myelinated axons. (a) An electrical model of a myelinated axon (b) Impulse propagation in the myelinated axon 1. An action potential is triggered at this node; we close the switch. 2. Once the switch is closed, the action potential emf drives a current down the axon and charges the capacitance of the membrane. The ion channels are located at the nodes. When they are triggered, the potential at the node changes rapidly to +40 mV. Thus this section of the axon acts like a battery with a switch. The myelin sheath acts like the dielectric of a capacitor C between the conducting fluids inside and outside the axon. Myelin sheath ww ww Conducting fluid ww 3. When the voltage on the capacitor exceeds a threshold, it triggers an action potential at this node-the next switch is closed. Ion channels The conducting fluid within the axon acts like a resistor R.
KEY CONCEPT FIGURE 23.50 A circuit model of nerve-impulse propagation along myelinated axons. (a) An electrical model of a myelinated axon (b) Impulse propagation in the myelinated axon 1. An action potential is triggered at this node; we close the switch. 2. Once the switch is closed, the action potential emf drives a current down the axon and charges the capacitance of the membrane. The ion channels are located at the nodes. When they are triggered, the potential at the node changes rapidly to +40 mV. Thus this section of the axon acts like a battery with a switch. The myelin sheath acts like the dielectric of a capacitor C between the conducting fluids inside and outside the axon. Myelin sheath ww ww Conducting fluid ww 3. When the voltage on the capacitor exceeds a threshold, it triggers an action potential at this node-the next switch is closed. Ion channels The conducting fluid within the axon acts like a resistor R.
Biochemistry
6th Edition
ISBN:9781305577206
Author:Reginald H. Garrett, Charles M. Grisham
Publisher:Reginald H. Garrett, Charles M. Grisham
Chapter32: The Reception And Transmission Of Extracellular Information
Section: Chapter Questions
Problem 14P
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In the axon model given, if the thickness of the myelin sheath were increased, the propagation speed of nerve impulses would
A. Increase. B. Decrease. C. Remain the same.
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