It is responsible for regulating muscle tone and maintaining posture and balance, the lowest level. An example of movements that are regulated by level A independently: involuntary trembling, chattering of teeth from cold and fear, fast vibrato in piano playing, trembling of the violinist’s finger, holding the pose in the flight phase of the jump and others. The anatomical substrate of this level consists of: the spinal cord with its cell formations and part of the conduction pathways; a group of cell nuclei in the brainstem (the group of the red nucleus with its two parts – palaeorubrum u neorubrum), substantium nigrum, Darkzewicz nucleus, Lewis’s body, hypothalami area, Deiters’ nucleus, ancient cerebellum and the central part of the autonomic (sympathetic and parasympathetic) apparatus.