What is atonia?

Atonia refers specifically to a state characterized by a lack of normal muscular tension or tonus. In this state, the muscles are unable to maintain their usual level of firmness or resistance. It is often associated with certain sleep stages, particularly REM sleep, where muscle tone is significantly reduced, allowing for a state of relaxation. This lack of muscular tension is essential for understanding how various conditions might affect motor functions, including those observed in patients with neurological disorders, sleep disorders, or certain forms of muscular dystrophy.

The other options describe different physical conditions: lack of coordination relates to motor skills, weakness refers to diminished strength in specific muscles or limbs, and partial paralysis indicates a loss of function in certain muscle groups rather than a general decrease in muscle tone.