The answer to the blank space to the question is sympathetic nervous system.
Sympathetic nervous system is a group of system that is famously associated with the fight or flights response. It is located in the spinal cord and it is associated with various organs in the body. It is part of the autonomic nervous system, together with the parasympathetic nervous system. This group of nervous systems, as implied by the name, operates automatically and regulates major bodily functions.