When cruise control 'hits the brakes', do the brake lights come on?

I go up and down a couple of mountains on one of my regular drives. If I’m using cruise control, it feels like it’s ‘stepping on the gas’ when going up, and ‘hitting the brakes’ when going down – in order to maintain a steady speed.

Do my brake lights come on when I’m going down a mountain? Is it noticeable from outside my car, in other words?