Those who challenge themselves have less blood vessel disease (allowing better blood flow to the brain), heavier brains, and more neurons.

Answer in a couple of paragraphs, 1 or 2 at the most if anything! 20 points + brainliest--> explain what all the systems in your body do to work together < --list of systems needed: circulatory systemrespiratory systemdigestive systemexcretory systemnervous system