system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why the electricity in our bodies can't power devices in our bodies (like a pacemaker).

I was thinking about this today, and I'm sure I'm not the first.

But what are the limiting factors in being able to power electric devices inside our bodies with the currents that are created naturally by our own bodies?

Do we naturally not supply enough energy or enough surplus energy? Do we not have the interface technology? Is it even theoretically possible?

Seems like it could be a gamechanger to utilize ourselves as a power source instead of needing to replace devices batteries (like a pacemaker).
gpt
> But what are the limiting factors in being able to power electric devices inside our bodies with the currents that are created naturally by our own bodies?

We don't produce that much electricity + there's no interface for it.

The whole heart is a natural pacemaker with particular nodes in it that have a tendency to pace faster than the rest of it, which basically sets your normal heart rhythm. We use pacemakers when the electrical activity doesn't conduct through your heart properly or there's a risk that it might spontaneously go into a rhythm that's dangerous for your heart. 

Electricity doesn't just like flow back and forth through our body, it has very directed and purposeful circuitry that serves to do certain things. It's not like we can just redirect current from some random part of our body to our heart - and even if we could - the energy used in pacemakers is much higher than what you'd normally find in your body. Plus, other than your heart, there's no natural capacity to regenerate the energy required for pacing that the pacemaker would require.

With minimally invasive surgeries today, a pacemaker can last quite a while and batteries only need to be replaced every few years in a minor surgery. They're not as large nor as problematic as they used to be in the past.