According to my studies, there's a whole load of nerve endings up there. It's a kind of reaction joint. It doesn't need any conditioned reflex.
12 seconds sound clip from the Drunken Dragon movie soundboard.
You can hear this line at 01:19:33 in the DVD version of the movie.
Quote context
[...]
- It's called letting off steam once the kettle is boiled.
- Granduncle, that's much too simple!
- Not your fist, you use your elbow.
- How come it feels like needles there?
- You don't huh? That's how they practice in the hospitals.
- Granduncle. It's not strong enough to attack.
- You just haven't got the reflexes yet, but it'll work if I use this!
[...]