Origin
SPs of C4-T4 (from C4-C6 via Ligamentum nuchae)
Insertion
Mastoid process
Lat 1/3 of superior nuchal line of occipital bone
Function
Ext of head at atlanto-occipital joint
Ext of neck at spinal joints
Lat flex of head
Lat flex of neck
Ipsilateral rot of head
Ipsilateral rot of neck
Nerve
Dorsal rami spinal nerves at corresponding level