
Homeostasis refers to a system's ability
to regulate its INTERNAL environment.
The Big Bang Theory Season 6, Episode 2

It’ll be the INTERNAL medicine doctor,
won’t it? I don’t know.
Money Heist Season 1, Episode 13

According to the head of INTERNAL medicine
Money Heist Season 1, Episode 5

creating a pair
of INTERNAL connecting rods,
The Big Bang Theory Season 7, Episode 15

I'm plagued by an INTERNAL struggle.
The Big Bang Theory Season 8, Episode 6