The gas pedal and the brake
Your autonomic nervous system runs two branches that work like a gas pedal and a brake. Watch what happens in the body as it shifts from one to the other.
Heart
110beats/min
Breathing
22breaths/min
Pupils
Dilatedlet more light in
Digestion
Pausedblood sent to muscles
01
Sympathetic
Fight or flight. The gas pedal.
When your brain reads danger, this branch gets you ready to act. It works in seconds, before you have time to think it through.
Side by side
| Sympathetic | Parasympathetic | |
|---|---|---|
| Job | Mobilize for threat | Restore, repair, connect |
| Heart | Faster and stronger | Slower |
| Lungs | Airways open, breathing quickens | Airways narrow, breathing slows |
| Eyes | Pupils dilate | Pupils constrict |
| Digestion | Slows; mouth goes dry | Speeds up; saliva flows |
| Energy | Liver releases glucose | Body stores energy |
| Messenger | Adrenaline and norepinephrine | Acetylcholine |
| Main route | Middle of the spinal cord | Vagus nerve, brainstem and base of the spine |
You can't control the weather. You can control how you sail through it.
Neither branch is bad. You need the gas pedal in a real storm. Trouble comes when the pedal stays pressed long after the storm has passed. A slow breath with a long exhale is one of the simplest ways to press the brake.