A Small caliber axon will have fewer potassium leak channels than a large axon a

Question

A Small caliber axon will have fewer potassium leak channels than a large axon as well as a thinner column of cytoplasm.

A.What effect will the smaller axon diameter have on membrane resistance and conduction velocity? Explain your answer.

B.What effect will the smaller axon diameter have on internal axial resistance and conduction velocity? Explain your answer.

C. How will these two changes in cable properties affect the overall axon conduction velocity and why? (Hint: membrane size is measured by circumference, while cytoplasm involves cross sectional area.)

Explanation / Answer

The velocity with which an action potential propagates along a membrane depends upon fiber diameter and whether or not the fiber is myelinated. The larger the fiber diameter, the faster the action potential propogates. This is because the larger fiber offers less resistance to local current, and so adjacent regions of the membrane are brought to threshold faster. Conduction velocities range from about 0.5 m/s for small diameterr, unmyelinated fibers to about 100 m/s for large diameter, myelinated fibers.

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