system
Given the following post, respond as if you're commenting on Reddit:
human
I hope this isn't a dumb question. I am taking ekg classes to further my education, and one lead on the machine I am using is the "ground". My question is this: what is the natural "ground" for the electrical activity in the heart?

Everything I have learned about closed electrical systems has come from working in an automotive shop for 15 years, and replacing or installing electrical outlets in my home. 

I do understand how the heart works, chemically and anatomically. I just can't seem to understand the grounding part. I have a BSN, but this was never touched on that I can recall. Google gives me nothing, no matter how I ask.

Edit: google, rrrrrr.
gpt
One thing I'd like to add is that voltage is used to measure a *difference* in potential. When you have circuits measuring change in potential caused by something like the heart, they need to compare this change to a baseline value. This value is often called ground, allowing different parts of the circuit to know how the input (or other components) potential is changing.