Final answer:
Compression of the sciatic nerve produces the sensation of a leg falling asleep.
Step-by-step explanation:
The sensation that your leg has "fallen asleep" is produced by the compression of the sciatic nerve. The sciatic nerve is a systemic nerve that extends across the hip joint and gluteal region into the upper posterior leg. When this nerve is compressed or irritated, it can cause numbness, tingling, and the feeling of your leg "falling asleep".