The connection between the CNS and the ANS is extremely important to understand, not only because it explains the manner in which emotions are generated and experienced, but also because the stress response is conducted along the same pathways. For example, the famous “Fight or Flight Response,” starts in the brain as an activation of the limbic system during conditions of stress. Stressful situations activate the limbic system which in turn sends messages to the heart, skin, pupils, blood vessels, breathing muscles, and muscles in the jaws, neck, and upper back. When a stressor is sudden and strong the response is generally widespread and profound.
Imagine that you are alone at night in an empty parking garage when you notice a man lurking behind your car. Immediately, your heart begins to pound, your breathing quickens. You halt. Your body is telling you not to approach. “Can I help you?” you call out from a distance. The man stands taller and you can see that he is big with a menacing look on his face. “Can I help you?” he responds threateningly.
This situation happened to a patient of mine, a woman who is not generally a fearful person. She described how her heart felt like it was coming up through her throat. She turned and ran. Fortunately, she was not chased. She returned to her office where a co-worker called the police. After investigating the scene and finding no one, they walked her to her car. She drove home feeling sick to her stomach. She said that she felt her face flushed as though embarrassed and her heart rate did not calm down for the rest of the night. She had trouble getting to sleep that night and has subsequently developed a fear of parking garages which she experiences as a racy-queasy feeling in her stomach and chest.
Imagine that you strained your neck and upper back after being rear-ended at a stop light. Your car was damaged and, even though it was returned to you “fixed,” it continued to make a rubbing noise every time you turned the wheel fully to the left while moving–a sound that was not there before the accident. Your primary care doctor gave you some anti-inflammatory medicines and you were told the pain would go away as your muscles healed over the next 2-4 weeks. But the medicines bothered your stomach and the pain did not go away, in fact it got worse and you started to have difficulty sleeping as well since you could not seem to find a comfortable position for your neck. Returning to your doctor, you were given a prescription for muscle relaxants to help you sleep, and a you were referred to physical therapist. The medicine helped you sleep but made you feel extremely tired and groggy in the mornings so you stopped taking it. At physical therapy you were given ice and electrical stimulation therapies and taught stretches for your neck and shoulders. You thought that you were feeling a little better after the first week but on the second week you noticed an escalation of pain. Your P.T. increased your frequency of care from twice per week to three times per week. Unfortunately your busy work schedule made impossible for you to get away from the office that often, and your boss made a comment about your work product of the the previous few weeks since the accident. The P.T. explained that without more frequent treatment she would not be able to help you with the pain.
One month post-accident, you receive a call from the insurance claims adjuster who questions the need for ongoing care. He tells you that the accident was a minor fender-bender, that statistically you should not have even been injured, that even those who do get injured only require on average three sessions of P.T. to get well. He informs you that a lot of people try to run up big bills in the hope of getting a better final settlement, but that the insurance company’s policy was to pay for only a maximum of three sessions. He offers you $500 to settle your claim and informs you that you have forty eight hours to accept the offer or it will be withdrawn. You hang up the phone and your neck and shoulders are so tight that it feels the muscles might tear. You have a terrible headache.
This event, taken as a totality, gives us the experience of stress, and it takes place automatically, irrespective of logic or reason.
When a friend sneaks up behind us and yells, “Boo!,” the sudden surprise rings a loud alarm in the emotional brain, causing a massive discharge of neurons which then mediate the following event: the muscles in our shoulders and neck tense suddenly, our heart beats fast in our chest, and our breathing quickens. This generalized state of arousal is called the ‘startle response,’ and is the first stage of the famous ‘fight or flight’ response which is hardwired into our nervous systems at birth. The combination of the loud sound, the suddenness of its intrusion into our otherwise calm environment, and the unexpectedness of it, lead to our emotional brain’s automatic interpretation of the event as a perceived threat. Once we find out that no authentic threat exists, that we’ve merely been teased by a friend, the startle response, rather than blossoming into a full-on state of fight or flight, recedes, while other emotions begin to rise. We may feel our cheeks flush (vasodilation of the blood vessels in the face, consistent with the feeling of embarrassment), our stomachs, shoulders, and upper back tighten (tensing of the muscles consistent with feeling hurt or angry). These feelings come and go without our request or consent, serving the will of the emotional brain (limbic system), not the thinking brain (prefrontal cortex). Acting through the ANS, the emotional brain is half-responsible for one of the great dichotomies of human existence: how we think and how we feel do not necessarily agree and in complex societies may often run directly counter to one another.