PHGY 213 Study Guide - Final Guide: Bradford Protein Assay, Nerve Conduction Velocity, Ventral Nerve Cord
19 Apr 2017
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Action potentials of the earthworm ventral nerve cord. Why send signals with action potentials: neuronal aps are not the only way for cells to communicate other ways include the diffusion of ions and hormones. This results in a relative refractory period, during which membrane is farther from threshold and is thus less excitable: the relative refractory period is preceded by a brief period in which the sodium channels are recovering from inactivation. The membrane remains hyperpolarized because the potassium channels are not as quick to return to their closed state. Increasing fiber size = increasing conduction velocity: presence/absence of myelin. In myelinated nerve fibers, the relationship is approximately: velocity (m/s) = diameter (micrometers) x 2. 5. The sign is negative because of the way the amplifier compares the inputs: thereotically, if the electrodes were sufficiently far apart, a short segment of 0 deflection could be recorded before the ap reaches the second electrode.
