origin and insertion: pairs of small muscles, anterior and posterior, on
 
 
 
 
each side of the spine joining the transverse processes of
 
 
 
 
adjacent vertebrae;  
they extend from the atlas to the 1st
 
 
 
 
thoracic vertebrae and from the 10th throracic vertebrae to the
 
 
 
 
last lumbar vertebrae;
action: acting unilaterally, lateral flexion of the spine; acting
 
 
 
 
bilaterally, extension and hyperextension of the spine;
nerve supply: anterior and posterior rami of the spinal nerves;
synergists: interspinalis, rotators, Multifidus groups;