system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How does the human heart seemingly keep going as a muscle without fail through years while other muscles in our body get fatigued within minutes or hours?
gpt
Cardiac muscle cells contain more mitochondria than skeletal muscle, meaning each cell has more available energy, making the muscle more resistant to fatigue. On top of this cardiac muscle has more readily available blood supply than skeletal muscle, allowing for better transfer of nutrients in and waste products associated with fatigue (like lactic acid) out.