Like the optic nerve, which tells your brain what's going on outside your body, your vagus nerve tells your brain what's going on inside your body. The vagus nerve is the brain's inner eye.

When ecstasy or fear take your breath away, that's your vagus nerve telling your brain you're not breathing much. When you try to calm your anxieties by drawing in a deep breath, your diaphragm is sending relaxation signals to your emotional brain along the vagus nerve.