A lot vs. Alot: 9 Grammatical Pitfalls
involuntary muscle n.
Any of the smooth muscles, except for the cardiac muscle, not under control of the will.
muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped cells with a single, centrally located nucleus. Smooth muscle tissue, unlike striated muscle, contracts slowly and automatically. It constitutes much of the musculature of internal organs and the digestive system.