The Elvis presentation

I just love finding out random stuff, especially when it bypasses my carefully acquired 42-year-old maturity and speaks directly to my inner child.

Like, as of today I now know that we all have twelve cranial nerves, i.e. nerves that don't exit the skull via the spinal cord but come directly through the skull itself.

More here by Jim Macdonald courtesy of Making Light.

One of these is the vagus nerve, which controls heart rate and hooks into various parts of the digestive system (among many other things). In fact it terminates at, um, the same point that the digestive system does. And stimulating the vagus slows the heart.

Thus, when you're having a really satisfying strain, this can apply pressure to the vagus and lower your heart rate. In fact it can lower it so far that, in the elderly or infirm, the heart can give up altogether. Hence the fact that so many heart attacks occur in that position.

This is known as the Elvis presentation after the most likely cause of the great man's death. The King upon his throne, as it were.

Mystery solved.