As previously stated, the reptilian brain controls our physical response to threat-flight, fight or freeze (these are all reflexes) . I’ve written often about tracking the sensations in the body; the language of the reptilian brain is sensation. Balance, initiation of movement, breathing, digestion, circulation, sleep, sexuality and action are all governed by this oldest part of the brain.
The reptilian brain-or brainstem-also effects the energy levels of the brain area above it; the limbic and cortex. It controls arousal, appetite, sexual engagement and sleep. When there is trauma in the body, the reptilian brain stays on ‘on’ and all these systems are impacted.