cervical spinal nerve 3 cervical spinal nerve 3 the cervical spinal nerve 3 (c3) is a spinal nerve of the cervical segment. cervical spinal nervethe plan of the cervical and brachial plexuses.the spinal cord with spinal nerves.detailsidentifierslatinnervi spinalisfma6444anatomical terminology it originates from the spinal column from above the cervical vertebra 3 (c3).