Your brain communicates with your body using nerve impulses, electrical signals propagated along axons. Axons come in two varieties: insulated axons with a sheath made of myelin, and uninsulated axons with no such sheath. Myelinated (sheathed) axons conduct nerve impulses much faster than unmyelinated (unsheathed) axons. The impulse speed depends on the diameter of the axons and the sheath, but a typical myelinated axon transmits nerve impulses at a speed of about 25 m/s, much faster than the typical 2.0 m/s for an unmyelinated axon. Figure P1.55 shows three equal-length nerve fibers consisting of eight axons in a row. Nerve impulses enter at the left side simultaneously and travel to the right. 

Data in Figure P1 .55 

a. Draw motion diagrams for the nerve impulses traveling along fibers A, B, and C. 

b. Which nerve impulse arrives at the right side first? 

c. Which will be last?

Transcribed Image Text:

Unmyelinated fiber A: Individual Partly myelinated fiber B: axons Fully myelinated fiber C: