“Some actions require split second responses–withdrawing a hand from a hot stove, for example. To relay the information necessary for such a reaction, there are large nerve fibers that can conduct impulses at speeds as high as 330 feet (100 meters) per second. Other kinds of activities, such as scholarly pursuits, may require a lifetime of thought. For these kinds of activities, other nerve fibers can be used to conduct signals more slowly–70 to 100 feet (20 to 30 meters) per second.”
Putting that in context, imagine a giant whose body was as tall as the continent of Africa is long (about 5,000 miles/8,000 km). If a shark bit him on the toe, it would take over 22 hours before his brain registered the pain and another 22 hours before his foot would receive the command to do something about it.