The heightened physical arousal that characterizes the fight-or-flight response involves the branch of the nervous system.

The heightened physical arousal that characterizes the fight-or-flight response involves the sympathetic branch of the nervous system (SNS).The sympathetic nervous system together with the parasympathetic nervous system form the autonomic nervous system.
SNS comprises the preganglionic fibers that issue from the thoracic and upper lumbar levels of the spinal cord.

1. is through mitosis2.dna replication