Muscle Tone

Anterior horn cells in the spinal cord send signals to muscles and determine muscle tone. Muscle tone determines reaction time: higher, well-regulated tone enables quick reactions, while low tone causes slow and delayed protective responses. The spinal cord has a built-in default inhibitory mechanism that restrains anterior horn cell activity to prevent muscles from going into spasm. The cortex regulates muscle tone through inhibition of inhibition: by suppressing the spinal inhibitory system, the cortex allows appropriate muscle activation. The cortex regulates not only voluntary movement but also the background muscle tone that keeps the body ready to respond.