I wonder if people who regularly donate blood are less likely to die from massive blood loss in an accident because their bodies are accustomed to 1. fabricating blood in response pint sized blood loss and 2. functioning with a lower than desirable volume of blood for brief periods.

Of course, no one can survive massive blood loss that isn’t soon controlled, but maybe the EMT’s lifesaving window of opportunity is a minute or so longer for a donor than it is for a non-donor victim of similar body type who has sustained the same injury.

When it’s said that using a part of your brain makes that part stronger, like muscles and exercise, does this mean that someone who enjoys REM sleep for more hours each night than someone else will have a brain that has stronger dream parts than the other person? And if a researcher says “The parts of the brain having to do with dreams have gotten stronger!” what does “stronger” mean? Do dreams become more vivid?