8x8x8 multiplexed LED cube with an Arduino Mega 2560

I have a really basic, but important question. The Arduino has some pins marked 5V and GND. See the group of pins which is leftmost on the bottom of the following image:

My question is: Are those 5V/GND pins directly connected to the power jack of the Arduino or the current passes through some circuitry in the Arduino before it reaches the 5V and GND pins? I'm asking because I want to determine whether I can feed my LED Cube Driver circuit from these 5V/GND pins of the arduino or I need to connect my LED Cube Driver to the real power supply's 5V and GND. As you know, my LED Driver Circuit can work with currents up to 1.3A and I'm wondering if it's safe to take that much current from the Arduino's 5V/GND pins...
It would be nice if I could feed my custom circuit from the 5V/GND pins of the Arduino because that way I would have only one power connector (on the Arduino), I would only need to solder some pin headers on my own custom circuit.

Thanks!