The Science of Stress: Living Under Pressure
176
The Science of Stress: Living Under Pressure
176eBook
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Overview
Jobs and families. Deluges of digital communication. The constant demands on our time and money. The screaming match of politics and the threat of terrorism and war. There’s no doubt we’re stressed out—but what exactly is it doing to us?
Neuropsychiatrists Gregory L. Fricchione, Ana Ivkovic, and Albert Yeung gently remind us in this book that persistent stress is directly linked to chronic ailments like heart disease, diabetes, and depression, contributing to one of the biggest health challenges facing the world in the twenty-first century. As they show, alleviating stress is a task no one physician can accomplish. It’s not the sort of problem a surgeon can excise with a scalpel or an internist can eradicate with antibiotics. It requires everyone’s efforts—the healthy, the sick, doctors, nurses, psychologists, clergy, community leaders, and beyond—to pull together to address the stress-induced drivers in our world that undermine our health.
Clearly and accessibly exploring the latest in modern neuroscience and immunology, the authors examine what those drivers are and how they reduce the body’s metabolic reserve, making us more vulnerable to illness. They then look at the antidote: enhanced resilience, something we can achieve by intelligently adjusting how we face the significant adversities that can spring up in so many facets of our lives. With innumerable insights on the personal and social causes of stress and its physiological effects, this book serves as an essential guide to properly taking care of ourselves.
Product Details
| ISBN-13: | 9780226338729 |
|---|---|
| Publisher: | University of Chicago Press |
| Publication date: | 12/22/2022 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 176 |
| Sales rank: | 758,417 |
| File size: | 19 MB |
| Note: | This product may take a few minutes to download. |
About the Author
Read an Excerpt
The Science of Stress
Living Under Pressure
By Gregory L. Fricchione, Ana Ivkovic, Albert S. Yeung
The University of Chicago Press
Copyright © 2016 Gregory L. Fricchione, Ana Ivkovic, and Albert S. YeungAll rights reserved.
ISBN: 978-0-226-33872-9
CHAPTER 1
INTRODUCING STRESS
Some of us enjoy the buzz of skiing down a steep mountain, while others thrill to sitting on the edge of our seats nervously watching a horror film. But would it be healthy to experience the excitement of extreme skiing or the spine tingling energy of a movie thriller all day long and every day? The molecules responsible for this extended buzz would soon take their toll on our health.
This chapter introduces the concept of stress and how experiences get processed in the brain to create a sense of tension and demand in the face of challenge and threat. We will explore the conduits that carry the message of stress from specialized brain regions down to our organs and tissues, effectively unifying our constituent parts into a whole organism capable of responding in our most important efforts to survive and prosper. But, if this system gets stuck in a vortex of continual stress responsiveness, a host of chronic stress-related diseases may emerge that can rob us of vitality through the debilitation of illness, and sometimes lead to premature death. Therefore, it is important for us to learn as much as we can about stress and its mechanisms.
LIFE'S JOB DESCRIPTION
What is stress?
The word "stress" carries negative connotations, and undue stress or prolonged stress can have very unfavorable consequences. However, to understand why stress can have such damaging effects, it is important to understand its true, more general meaning. Stress is a living thing's response to changing circumstances in its immediate environment. It is a "sense-analyze-decide-respond" system that is necessary for survival.
All living things have innate mechanisms for sensing and analyzing "stressors." A stressor is anything that could threaten an individual's well-being. In the case of a single-celled organism, a stressor might be a toxic chemical compound. Cells have receptors on their membranes that feed information about the stressors into the cell — and the internal machinery of the cell crudely analyzes the information and the cell responds. For example, a bacterium will move away from toxic chemicals.
Human cells have protective mechanisms at the cellular level, just as bacteria do. But as complex multicellular organisms, we can analyze and respond to complex situations about which bacteria would be unaware. For example, we can read aggressors' behavior to predict an impending attack and try to move out of the way. For these kinds of stressors, our sense-analyze-decide-respond system is centered on the nervous system. Nerve endings in the skin, eyes, ears, mouth, and nasal passages do the sensing, and convey information to the brain. In the brain, various structures do the hard work of analyzing, deciding, and responding to stressors. The response is carried out via neurons that connect to organs and muscles, or to hormone-producing glands around the body. Generally, a stressful situation will cause the brain to become more alert and prepare the body for action.
SENSE, ANALYZE, AND RESPOND TO STRESS
The brain is at the center of our reaction to stressful events. It receives sensory inputs from the outside world, makes sense of them, and then reacts accordingly: by moving muscles, regulating body systems, and by producing hormones. Most sense inputs feed into a region of the brain called the thalamus. It communicates with the cortex — the wrinkled outer part of the brain — and also with the limbic system, which controls the brain's emotions and drives. The cortex initiates muscular movements, while the limbic system regulates the release of hormones and controls functions such as heart rate and pupil dilation.
Good stress
A little stress is a good thing. Not only can it keep us alive, it can also improve our performance when we carry out a task, or improve our learning of a new skill. This idea was first analyzed scientifically by American psychologists Robert Yerkes (1876–1956) and John Dodson (1879–1955). They measured the increases in performance in people who had been presented with challenges, and whose brains and bodies had become alert and ready for action, or "aroused." Their findings can be summarized as a simple curve of arousal versus performance (see below). The state in which a living thing is functioning well and dealing with — or even benefitting from — a variety of everyday stressors is called "eustress."
Bad stress
However, not all stressful situations are good — and not all stress is beneficial. When there is too much arousal, or too much pressure of one kind or another, performance suffers.
When the challenges of life escalate and we feel threatened, we are often faced with what is called toxic stress or "distress" — the opposite of eustress. When we do not have enough to eat, lose our jobs or homes, or our relationships falter, we experience emotions and have thoughts that are accompanied by physiological and hormonal markers of our disquiet. In addition, we can fall victim to internal drivers of our distress. For example, we may worry about future challenges. Feeling anxious about whether or not we can meet these challenges, and brooding on past failures, can further exhaust us with toxic stress. So, for many reasons, our system may come up short, and this is when distress can set in.
THE HISTORY OF STRESS
What does stress mean?
Homeostasis: Maintaining internal stability
The first description of stress as a concept is commonly attributed to the French physiologist Claude Bernard (1813–78). In 1865, he presented the idea that an organism is comprised of an internal environment made up of cells called the milieu intérieur or "interior milieu." This milieu is tightly controlled through a series of feedback mechanisms based on information flowing in from the external environment. Then, in the early twentieth century, American physiologist Walter B. Cannon (1871–1945) introduced the concept of "homeostasis," by which he meant the way in which the body maintains its internal equilibrium even when it is faced with external difficulties.
In his study of one major part of the response to stress, namely, the sympathetic nervous system (SNS), Cannon came to realize that organisms adapt by compensatory responses when faced with challenges to their internal stability. For example, missing your bus with the threat of being late for an important business meeting will lead to a whole host of internal physical changes, many brought about by the sympathetic nervous system. This system has its source in one of your brain stem nuclei called the locus coeruleus — the blue location — named because its melanin granules stain blue in the laboratory. From there, sympathetic nerve fibers track to your lateral hypothalamus and down the spinal column to exit into nerve bundles called ganglia, which then supply your organs and muscles with action responses. An acute challenge to your well-being will ignite an outpouring of energy-demanding chemical messengers (seealso) which enable you to make every effort to survive in, what Cannon dubbed, a "fight-or-flight reaction." But when the challenge stops, your body is expected to restore a homeostasis (return to equilibrium) with a different chemical profile that is more in keeping with a sense of security, and energy conservation.
The term "homeostasis" is meant to emphasize that organisms can maintain a multitude of physiological variables such as blood glucose, oxygen tension, blood pressure, heart rate, and core temperature, within acceptable ranges for health. This feature of successful living requires the presence of feedback systems. Sensors are necessary to gauge when physiological values are out of bounds, and effectors are necessary to bring them back to normal. Think of your thermostat at home. It is a homeostatic device in a way. When it senses a temperature plunge, a feedback loop ignites your heating system to maintain a temperature homeostasis in your home.
In human beings, when we get cold, shivering commences and blood is redirected from surface vessels back to inside the body. On the other hand, when our core temperature rises, we sweat and blood is shunted from our internal organs (viscera) to the skin so that heat can escape. It is felt that many threats to homeostasis, such as intense cold, blood loss, low glucose, trauma, and psychosocial distress, would all induce a response from the fight-or-flight system, which comprises the sympathetic nervous system and the medulla part of the adrenal gland, in an effort to restore our safety. This so-called adrenergic system runs on neurotransmitters called catecholamines (epinephrine and norepinephrine, also called adrenaline and noradrenaline).
Neurotransmitters are chemical messengers that exchange information through actions at post-synaptic receptors that establish (binding) connections between neurons. Whether we change posture, eat a dinner with gusto, tackle a mugger, or need to give a speech in front of a group of strangers, our nervous system will be activated through the actions of these neurotransmitters.
COMING IN FROM THE COLD
The stress of the cold temperature has affected the mountaineer's physiological response. He has maintained homeostasis by shunting blood flow to his internal organs, while at the same time reducing skin capillary blood volume on the surface, and conserving energy by reducing as best he can highly charged emotional displays.
THE CONCEPT OF STRESS
What is the HPA axis?
Hans Selye (1907–82) was a Hungarian scientist, who in 1956 popularized the concept of stress. The word "stress" originates from the Latin word strigere meaning to tighten. Selye adapted the term, which was used in engineering to denote a deforming force that results in structural strain, and he applied it to the organism's response to internal and external disturbances called "stressors." Stress became "the nonspecific response of the body to any demand upon it."
No matter what type of stressor an organism encounters, Selye contended that the body's stress response is liable to be composed of a set of similar features. This became known as "the non-specificity hypothesis." Selye's concept stood in opposition to a psychoanalytic concept that specific stressors gave rise to specific stress responses culminating in specific diseases.
THE FIGHT-OR-FLIGHT RESPONSE
The trauma of being in a war zone is one of the most extreme stressors that a person can experience and many combatants go on to develop post-traumatic stress disorder (PTSD) when their acute, war-induced stress response persists past three months. The stereotypical example of fight-or-flight stress is depicted in this classic painting, The Death of Major Peirson, 6 January 1781 by John Singleton Copley.
The HPA axis
Selye proposed three phases involved in coping with stress: first, an alarm reaction strikes us, not unlike the concept of the fight-or-flight response; second, we adapt to the stressor, often by resisting it and seeking a return to homeostasis; in the third stage, we run the risk of exhaustion if the stressor is prolonged or catastrophic. Our resistance to stress owes to a major stress response system comprised of three hormonal nodes: the hypothalamus (H), the pituitary (P), and the adrenal cortex (A), called the "HPA axis" for short. The output glucocorticoid hormone is called cortisol in the human. This extremely important stress hormone contributes to stress resistance and a return to homeostasis, but can also provoke illness when its production is excessive or persistent.
Selye proposed that the body could change its set point to a new steady state goal in an effort to resist unusually high demands. He called this process "heterostasis" (hetero from the Greek for "other"); and he felt that mind–body stress reducing approaches, which enhance our body's natural defenses, while not curative, can have the benefit of changing the set point and maintaining health. Today, we can think of integrative mind–body approaches as heterostatic in their effects.
HOW THE HPA AXIS WORKS
When the amygdala perceives sensory information from the thalamus to be threatening, it engages the paraventricular nucleus in the hypothalamus resulting in the stimulation of corticotropin-releasing hormone (CRH), which begins the stress hormone cascade. This hormone then stimulates the pituitary to release another hormone called adrenocorticotrophic hormone (ACTH). This hormone travels down to the adrenal cortex gland, which produces the stress hormone cortisol. Cortisol in turn will feedback to the hypothalamus and the pituitary.
THE BIOLOGY OF COPING WITH STRESS
What happens to the body under stress
In the latter part of the twentieth century adjustments needed to be made to Selye's concepts of stress, as understanding had developed. First, it became clear that the idea of a uniform general stress response, regardless of the specific nature of the stressor, needed refinement. A stressor — for example extreme cold — will stimulate your sympathetic nervous system while allowing your other hormonal responses to remain relatively dormant.
It has also been recognized that homeostatic physiological systems are multiple, interactive, and dynamic, responding in a real-time way to external and internal fluctuating demands. Stress reflects a discrepancy between expectations, which are products of your genetic predispositions, developmental learning, and analysis of the present state of affairs, and your anticipated perception of environmental demands. This discrepancy leads to patterned and compensatory responses on your part.
Today, many researchers conceive of stress as the perceptual aftermath of a threat to your security and homeostasis. The stress response to specific stressors has both specific and non-specific components. Variables include the nature of the challenge to your homeostasis, your appraisal of the stressor, and the optimism or pessimism you associate with the task of coping with it.
Allostasis
Physiologists (Sterling and Eyer in 1988) coined the term "allostasis" to capture this new notion of stress-responding physiological systems in the case of blood pressure control. Allostasis, as researcher Bruce McEwen points out, means "maintaining stability, or homeostasis, through change." Thus, changing environmental conditions leads to variable physiological and hormonal states that enable you to meet your separation challenges in a safe and effective way without wild or persistent fluctuation from the set point. A good example of allostasis is the well-known finding of heart rate variability. The heart's physiology is considered healthier when the beat-to-beat heart rate interval, as measured in the electrocardiogram, fluctuates over time in response to environmental demands. A heart that does not alter its contraction rate reveals pathology in its lack of dynamic stability, adverse cellular dynamics, and poor evaporative mechanisms.
Moderate exercise permits allostatic mechanisms to predict your metabolic needs and to meet them in a balanced fashion. Excessive exercise, on the other hand, can lead you to experience a host of negative physiological changes by producing an allostatic challenge. Your body might then enter a catabolic breakdown state rather than an anabolic build-up state. You may become dehydrated, low in glucose and oxygen saturation. Cells may begin to undergo anaerobic (without oxygen) respiration, which releases lactate and leads to a phenomenon known as lactic acidosis. This can cause spasms and aches in your muscles, lack of concentration, general fatigue and shortness of breath. In this context, muscle cell can breakdown, which can lead to kidney dysfunction. Proteins and calories may rapidly deplete leading to deficiencies. Cortisol may persistently elevate, resulting in vulnerability to mood changes and infections. Heart rate variability may decline and the body may begin to feel tired as fatigue sets in.
Three typical responses to stress
The allostatic process is supervised by our brain and requires a large expenditure of energy. When someone is threatened by overwhelming stress, for example from experiencing an acute traumatic event such as a bomb exploding, or a more persistent stressor like losing your home, tremendous metabolic strain will lead to disease vulnerability. We suffer "metabolic wear and tear" if we are forced to continually expend energy when responding to repetitive stress. "Allostatic loading," as it is also known, can be thought of as the price the body pays for being forced to adapt to adverse psychosocial or physical situations.
As opposed to the idea that the stress response will always be the same, the concept of allostasis allows for an element of specificity in your stress response. For example, the predominant specific responder system to activate in situations of blood pressure changes will be the sympathetic nervous system. In contrast, when you experience a deprivation of glucose or emotional distress, the adrenal medulla will be the predominant responder.
However, three general allostatic stress responses can be recognized. First, stressor and response may be well-matched resulting in a return to homeostasis (resilience through allostasis). Second, an overblown, continual response may cause us to veer off into danger zones (vulnerability due to allostatic loading). And third, the match may be optimal leading to a new, stronger set point (post-traumatic growth or anti-fragility). Post-traumatic anti-fragility emerges when, though the threat is enormous, we find within ourselves the strength to emerge in a wiser and stronger position.
(Continues...)
Excerpted from The Science of Stress by Gregory L. Fricchione, Ana Ivkovic, Albert S. Yeung. Copyright © 2016 Gregory L. Fricchione, Ana Ivkovic, and Albert S. Yeung. Excerpted by permission of The University of Chicago Press.
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Table of Contents
1. Introducing Stress
Gregory L. Fricchione
2. Stress and the Brain
Gregory L. Fricchione
3. Stress and the Cardiovascular System
Gregory L. Fricchione
4. Stress and the Immune System
Albert S. Yeung
5. Stress and the Sleep Factor
Albert S. Yeung
6. Stress and Women’s Health
Ana Ivkovic
7. Stress and Nutrition
Ana Ivkovic
8. Stress, Health, and the Social Experience
Albert S. Yeung
9. Facing Fear: Resilience and Post-Traumatic Stress
Albert S. Yeung
10. The Mind-Body Medical Equation and Public Health
Gregory L. Fricchione
Glossary
Selected Bibliography
Index
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