The answer is 250 miles per hour.
To communicate, neurons send impulses to other neurons or muscle cells. Depending on the nature of information needed to be sent, some impulses are faster than the other. For example, if a person burns its hand, the information must be quickly sent to the central nervous system for quick reaction. Some impulses can achieve 250 miles per hour. But, for this, axon must be well insulated and very thick.