system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can your heart beat constantly and not get tired when skeletal muscle gets tired after a relatively short period of time?

Your heart beats 60+ times a minute every minute from before your born untill you die, why can it beat without getting tired when skeletal muscle gets tired after a few hours of work? Why cannot skeletal muscle do the same?
gpt
Thats because the hearts cells have much more  mitochondria than any other skeletal muscle. Since the heart has so much power from the mitochondria, it doesnt need to rest. And as its working, it keeps recieving different nutrients from all the blood thats pouring into the heart. 
Hope that helps!