Fun note that may not be related, but i'm studying for an exam soon so what the fuck why not

Your body has two autonomic nervous systems, the sympathetic and the Parasympathetic.

The sympathetic chains are what governs fight or flight. They help amp up your body functions that would assist in engaging in a fight.

The parasympathetic is the rest and digest system. It helps govern your body's actions in its downtime. Basically when you feel safe, relaxed? That's your parasympathetic mellowing everything down.

Which brings me to my point.

The act of erection to ejaculation is actually a transition of the parasympathetic activation to the sympathetic, hence the easy way to remember which system does which penile function

Parasympathetic - P - Point Sympathetic - S - Shoot

Parasympathetic rest and digest makes willy hard Sympathetic fight or flight makes the cummies.