The dorsal vagal branch

The dorsal vagal branch is the arm of the vagus nerve associated with shutdown and protection. According to polyvagal theory, when danger seems too great or escape impossible, the nervous system can resort to this branch; the result is a state of withdrawal, numbness, or collapse. This is the oldest and most primitive protective response; the body protects itself by, as it were, closing down. The dorsal vagal state shows itself in low arousal and turning inward. This response is not a weakness but the system's last-resort form of protection.