Spasmolytics are group of drugs that decrease the muscle tone in the neurological diseases but the active contraction not affected. So, what the difference between muscle tone and the contraction?
Muscle tone is a reflex that is initiated by stimulus (stretch) — > receptor (muscle spindle) — > afferent (sensory nerve) — > center (anterior horn cell) — > efferent (motor nerve) and effector (skeletal muscle). This reflex is under higher centers control (e.g. thorough the extra-pyramidal tracts) as well as peripheral control (e.g. sensory input that terminates on GABA pre-synaptic receptors on the afferent limb of the reflex). Active movement is initiated from the motor area in the cerebral cortex and impulse descends through the pyramidal tract to the anterior horn cell — > motor nerve — > Skeletal muscles. It is to be noticed that both Muscle tone and Active movement common part of the pathway (written in red). Drugs which act on this part e.g. neuromuscular blockers will affect both tone and movement while drugs which act on control sites of muscle tone will affect the muscle tone only e.g. spasmolytics. Both in muscle tone and active movement of the skeletal muscle there
