Figure 23-33. Different stereotyped pathways are taken by the axons of sister neurons.

Figure 23-33Different stereotyped pathways are taken by the axons of sister neurons

(a) Each of the 17 segments of the grasshopper embryo have two segmental ganglia; these ganglia have a virtually identical pattern of nerve differentiation. One identifiable neuroblast in each half of each segment divides repeatedly to form about 50 ganglion mother cells, each of which divides to yield two sister neurons. The first six neurons formed, shown here, extend axons across the ganglion, forming part of a transverse fascicle. The growth cone of each neuron then recognizes a different longitudinal fascicle and moves along it, elongating the axon in a specific direction. (b) Details of the selective fasiculation of the growth cone of the identifiable G neurons. Each half segment has one G neuron, whose axon grows along a transverse fascicle to the opposite side of the embryo. There the G growth cones explore the surfaces of 25 fascicles with a total of 100 axons. The G growth cones adhere to and migrate along only the axons of the P1 and P2 neurons (blue) in the A-P fascicle (green and blue axons). [After C. S. Goodman and M. J. Bastiani, 1984, Sci. Am. 251(6):58.]

From: Section 23.5, Overview of Neuronal Outgrowth

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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