But bones are unable to move on their own, so muscles pull on them at joints. Cardiac muscle cells contract and relax to pump blood around our bodies. Smooth muscle cells make up thin sheets of ...

Involuntary cardiac and smooth muscles are responsible for contraction of the heart and movement of substances through hollow organ systems, respectively, and voluntary skeletal muscles are ...

Botox injections work by blocking a neurotransmitter that signals muscles to contract ... really deep and it looks pretty flat and smooth… It kinda worked… Or, maybe it’s just placebo ...