I’m continuing my reading of the book “Why Zebras Don’t Get Ulcers” and today came across some interesting tidbits about a special focus of this blog: penises.

Specifically, in a chapter on how stress affects reproduction, the book goes into great detail on how erections work.

First, we should understand that your nervous system — the complex pathway of chemical signaling that controls things like your heart rate, digestive system etc. — has two components. There’s the sympathetic nervous system which is basically what fires up when you get anxious or panicked. And there’s the parasympathetic nervous system which is what’s firing up when you’re chilling out.

By a strange twist, it’s actually your parasympathetic nervous system which needs to be activated to get an erection. However, it’s your sympathetic nervous system that signals for the act of ejaculation. So, during the complex process when you are pounding away at a sleazy Thai hooker, err, I mean, your darling wife, the two components of the nervous system have a delicate interaction. One must first be turned on, then turned off, whereas the other starts off off, and then turns on.

It’s a wonder it works at all.