The HPA Axis

Stressed Driver

Stress happens. It’s unavoidable. But what is really happening inside of us and what can we do to mitigate its damaging effects? That is exactly what we hope to teach you in honor of stress awareness month!

It has happened to us all. We’re driving down the road thinking about what we might do for supper when we see a flash of motion coming up on our right. Instantaneously, our heart beats wildly in our chest as a surge of energy floods our body leaving us momentarily breathless as our muscles grip the steering wheel and deftly maneuver left.  This is in perfect coordination with our feet hitting the brake just enough to evade the reckless invasion of our lane by a road-raged individual, but without getting slammed from behind or swerving into the driver we just passed on the left!  Whewph!  As if waking from an altered state in which something else took over our driving for that critical 3 seconds, we suddenly become aware of the sweat beaded on our brow and our rapid breathing as conscious thought regains control and we utter under our breath our first real thought, “Thank you God,” or a rapid string of expletives. Five to twenty minutes after our knuckles are no longer white as we have relaxed our grip and the breathing and heart rate slowly come down, finally the swirl of stimulatory chemicals keeping us in hyper alert ebb and we start to feel normal again.

What just happened? Your daily commute in Houston traffic, you say?  Well, unfortunately it may be true that you experience nearly daily stressors like this, but what is happening on the inside? You just experienced the life-saving effects of your autonomic nervous system (ANS)!  The ANS controls everything that you don’t actively think about doing. For example, you think about jumping up to greet a friend, but you don’t think about adjusting your blood pressure so that when you do, all your blood does not drop to your feet resulting in you passing out instead! The ANS has 2 parts to it called the sympathetic and parasympathetic systems. These systems have nearly opposite effects on the body (see chart below).  And while both are always active, they tend to work like a seesaw. When one goes up the other’s activity goes down.

CNS

In the scenario that I gave, the brain perceives a threat due to visual input and slammed the big red alarm button of the brain called the amygdala (think of it as your brain’s fear center) and this signaled your hypothalamus (the command center of the brain) to “put all hands on deck!” It therefore activated the ANS to increase sympathetic activity, and the nerves of the sympathetic system that stimulate your adrenals jolted them into releasing that intense release of neurotransmitters (norepinephrine and epinephrine) that we refer to as adrenaline in the classic “adrenaline rush”.

Those neurotransmitters stimulate every organ to initiate the stress responses for each organ, thus the heart beats faster, eyes dilate, muscle tone strengthens, and your liver floods your bloodstream with stored glucose to fuel them to “fight or take flight” and perform whatever action is needed to save your life.  All this neurological activity happens in a fraction of a second giving you the ability to react before you fully comprehended what your threat was! Once the threat is perceived to be averted, and your brain is convinced of safety, the parasympathetic system takes back the wheel and starts driving your body back into a more restful state and returns its attention back to the normal daily activities of digesting, etc. Thus it is known as the Rest and Digest System . Not only does it put the brakes on the sympathetic system, but it also acts as a shock absorber. For example, have you ever got a scare so bad that after you calmed down a little bit, you suddenly started shaking uncontrollably (ladies, this is the same shaking that occurs shortly after laboring in childbirth)?  What is happening is that the parasympathetic system uses your large muscles to clear the blood of the excess adrenaline in this repetitive contractile motion, and therefore bring relaxation in the form of muscle fatigue. Note also that while exercise tends to activate sympathetic activity (stress response), it also has stress-relieving and sleep-improving effects on the body via similar mechanisms.  An adrenaline rush does not actually raise cortisol, however, because the split-second reaction time requires the nerves to deliver the stress message directly to your adrenals. But if the threat persists, or as in cases of even low-grade chronic stress, the hypothalamus activates the second part of the stress response system called the hypopituitary adrenal axis or HPA axis. It is named for the communication line that activates when the hypothalamus releases corticotropin releasing hormone, which stimulates the pituitary glands in the brain to release adrenocorticotropic hormone (ACTH), which then travels to the adrenals prompting them to release cortisol.  This hormone cascade from the brain can also provoke a powerful stress response in the body through its own stimulation of the sympathetic nervous system that can be sustained for hours or even days allowing the body to endure hardships such as being stranded in the ocean without option of food or sleep until rescued. Thus, it is also intended to be lifesaving!

Adrenal Diagram

Stress that becomes truly chronic, however, can keep the HPA axis activated enough that the sympathetic system becomes dominant or active most of the time, chronically depleting your internal resources and causing inflammation and deterioration of your organ systems into diseased states such as developing anxiety, high blood pressure, obesity, accelerated aging, cancer, etc. Fortunately (and perhaps unfortunately), you are human, so this gets much more complicated.  First of all, if daily stressors we experience (most of which are not actually life threatening) can induce anxiety disorders and physical disease, why aren’t animals who constantly have to find food (and keep from being food) coming in droves to visit doctors and psychiatrists!?

Current research seems to support a new understanding of the parasympathetic system that is being called the polyvagal theory. This theory is based on the idea that the vagal nerve (cranial nerve #10), which controls almost all the parasympathetic influence of our organs, has 3 functionally different but interconnected parts. The second part is the traditional rest and digest function, but the first part is thought to regulate our expressions of emotion and social behavior. The 3rd part is considered the last resort responses such as death-feigning and is seen more in the non-human animal kingdom, so I don’t plan to discuss it.

Significantly, the social engagement system (first part) is actually believed to be able to override the sympathetic system and HPA axis! The basic idea is that social cues and environmental context surrounding a threat changes the degree of reaction to that threat or may even nullify the threat completely. For example, a child experiencing a thunderstorm in his own bedroom alone may become terrified, setting off the typical flight or fright response.  However, if he were to run to his parents’ bedroom and crawl into their arms he could become so comforted by the change of environment, namely social support (my parents are in this with me) or the perceived reduction in the threat (my parents can protect me from whatever badness the storm can bring), that they fall fast asleep with the storm still rocking the windows.  The threat did not change, but the parasympathetic response was able to dominate simply due to social/environmental modification.  Likewise, if in my original traffic scenario we choose to respond with gratefulness (“Thank God”) and choose to see our fellow humans through the lens of grace or compassion (“Maybe that was a new father-to-be rushing his laboring wife to the hospital…”) we can change our whole emotional response and therefore shut down our amygdala (fear center) much more quickly and restore emotional and spiritual homeostasis as well. 

Thus, this theory begins to explain the possible physiology behind many effective therapies we currently have to reduce stress. For example, the comfort people get from companion animals who don’t in and of themselves actually change any stressful situation generally. It also helps us understand how therapies like counseling, gratitude journals, appreciation of nature, prayer, meditation with imagery, and even helping others can help us to de-stress.

Anything that helps us to change our environment to be less threatening, more loving or meaningful, or to reframe past or present stressors in a new and positive light, can empower us to use our parasympathetic nervous system and restore our bodies back to balance again.   Be sure to read our April 2019 Whole Health Herald, especially the section on EVOX, and come along with us for the remainder of this month as we explore this topic of stress responses and stress management more in depth in subsequent blog posts. 

 

Leave your comments below!

 

Yours in Whole Health,

Dr Wells

About the Author

Valeska Wells, D.O.

Dr Wells is medical director at Whole Health Center Houston - of one of the longest standing functional medicine clinics in Houston, Texas.

Born and raised in Fredericksburg, Texas, Dr Wells is a Christ-centered, family-oriented physician who has known from an early age that medicine is her calling. She studied medicine at the Texas College of Osteopathic Medicine in Fort Worth. During medical school she also completed an intensive fellowship in Osteopathic Manual Therapy and she became certified in Medical Acupuncture. She completed her residency at UTMB Galveston, wherein she also completed Andrew Weil’s Integrative Medicine in Residency curriculum through the University of Arizona.  Dr Wells draws on her extensive clinical and educational background to educate her patients on their options and then working closely with them to achieve healing and wellness. 

When she is not caring for patients or writing articles, Dr Wells enjoys spending time with her husband and four children.  She and her family are practically urban farmers and homesteaders with a handful of chickens, a large garden, and ambitions of adding a couple of goats to the family soon!  

About the Author

Valeska Wells, D.O.

Dr Wells is medical director at Whole Health Center Houston - of one of the longest standing functional medicine clinics in Houston, Texas. Born and raised in Fredericksburg, Texas, Dr Wells is a Christ-centered, family-oriented physician who has known from an early age that medicine is her calling. She studied medicine at the Texas College of Osteopathic Medicine in Fort Worth. During medical school she also completed an intensive fellowship in Osteopathic Manual Therapy and she became certified in Medical Acupuncture. She completed her residency at UTMB Galveston, wherein she also completed Andrew Weil’s Integrative Medicine in Residency curriculum through the University of Arizona.  Dr Wells draws on her extensive clinical and educational background to educate her patients on their options and then working closely with them to achieve healing and wellness.  When she is not caring for patients or writing articles, Dr Wells enjoys spending time with her husband and four children.  She and her family are practically urban farmers and homesteaders with a handful of chickens, a large garden, and ambitions of adding a couple of goats to the family soon!  

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