Research Article
Physiology and Anatomy of Stress Manish Kumar Dwivedi*, HH Awasthi** Abstract The problem of stress remains a contentious issue. It depends on the way the stress is defined and how the concept of health is viewed. Scientists accept this as a physical environment can act as source of stress causes illness, disease or death. Stress can produce physiological and psychological changes that lead to illness through direct route.3 Stress is the pattern of specific and non-specific responses an organism makes to stimulus events that disturb the equilibrium and taxes the ability to cope. It disturbs the mental and physical level of an individual affecting various parts of the brain and related body parts. Psychophysiology is a field of study based on the principle that the mind and body are one, where thoughts and perceptions affect potentially all aspects of physiology. This study examines the effects of stress on the various parts of the body and the mind.
Keywords: Stress, Hippocampus, ACTH axis. Introduction
The Vegetative Level
Hens Selye proposed the direct relationship between chronic stress and its effects on the various body parts. The physical deterioration of the body has been noticed the attention of the physiological dynamics involved with stress response specifically the immediate, intermediate and prolonged effects on the body. The psychophysiology explains the concept of mind-body relationship and supports the fact that many diseases and illness occur due to psychosomatic disorders in the mind through the higher brain centers. There are three systems in the body which are directly involved with the physiology of stress: the nervous system, the endocrine system and the immune system that are stimulated by the perceived threats.1
The lowest level of the brain consist of two parts the reticular formation and the brain stem. The reticular activating system consist of fibers that link connecting the brain to the spinal cord, it acts as a bridge and communication link joining the mind and the body as one. The brain stem composed of the pons, medulla oblongata and mesencephalon is responsible for involuntary functions of the human body such as heartbeat, respiration and vasomotor activity.1
Central Nervous System The brain plays a critical role in the body’s perception and response to stress. The brain carries information of stressful situations across regions of the brain, it would help to explain how stress and its negative consequences are responsible for neutral communication dysfunction. The nervous system has two parts: the Central Nervous system (CNS) consists of the brain and spinal cord and the peripheral nervous system comprising of neural pathways. The human brain is divided into three levels: the vegetative level, the limbic system and neocortical level.1 *
The Limbic System The midlevel portion of the brain is limbic system. The limbic system controls the emotions in the body responsible for biochemical reactions constitute the stress response system. The limbic system composed of the thalamus, the hypothalamus, the amygdale and the pituitary gland known as master gland helps to maintain a level of homeostasis within the body.1 Homeostasis is a physiological state of complete calmness or rest, it include heart rate, blood pressure and ventilation. The hypothalamus is a small portion of the brain located below the thalamus and above the brainstem. One of its most important functions is to help link together the body’s nervous and endocrine systems. This structure has many bidirectional neural inputs and outputs from and to various other brain regions. These connections help to regulate the hypothalamus’ ability to secrete
Ph.D Scholar, Department of Rachana Sharir, IMS, BHU. Head & Professor, Department of Rachana Sharir, IMS, BHU. Correspondence to: Mr Manish Kumar Dwivedi, Ph.D Scholar, Department of Rachana Sharir, IMS, BHU. E-mail Id:
[email protected] **
© ADR Journals 2015. All Rights Reserved.
J. Adv. Res. Ayur. Yoga Unani Sidd. Homeo. 2015; 2(3)
hormones into the body’s blood stream, having farreaching and long-lasting effects on physiological processes such as metabolism. During a stress response, the hypothalamus secretes various hormones like corticotropin-releasing hormone, which stimulates the body’s pituitary gland and initiates a heavily regulated stress response pathway.2 The amygdala is a small, "almond"-shaped structure, two of which are located bilaterally and deep within the medial temporal lobes of the brain. The amygdalae are part of the brain’s limbic system, with projections to and from the hypothalamus, hippocampus, and locus coeruleus among other areas. Thought to play a role in the processing of emotions, the amygdalae have been responsible for modulating stress response mechanisms, particularly when feelings of anxiety or fear are involved.2
Hippocampus The hippocampus is a structure located bilaterally, deep within the medial temporal lobes of the brain, just below each amygdala and is a part of the brain’s limbic system. The hippocampus is thought to play an important role in memory formation. Hippocampus is connected to the cerebral cortex, hypothalamus, and amygdala, among other regions. During stress, the hippocampus is particularly important, in that cognitive processes such as prior memories can have a great influence on enhancing, suppressing, or even independently generating a stress response. The hippocampus is also an area in the brain that is susceptible to damage brought upon by chronic stress because of which people suffer from a problem of memory loss very soon.2
The Neocortical Level The neocortex is the highest and most sophisticated level of the brain. At this level the sensory information is processed as a danger or non threat and cognition takes place. In close association with Central Nervous System, the other neural fibers are considered to be peripheral nervous system comprises of two individual networks: somatic networks and autonomic nervous system. The somatic networks are responsible for transmitting sensory messages along the neural pathways between the five senses and the higher brain centers while the Autonomic Nervous system regulates the function of circulation, digestion, respiration and temperature regulation.1
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Prefrontal Cortex The prefrontal cortex, located in the frontal lobe, is the anterior-most region of the cerebral cortex. An important function of the prefrontal cortex is to regulate cognitive processes including planning, attention and problem solving through extensive connections with other brain regions. The prefrontal cortex can become impaired during the stress response.2
Locus Coeruleus The locus coeruleus is an area located in the pons of the brainstem that is the principal site of the synthesis of the neurotransmitter norepinephrine, which plays a crucial role in the sympathetic nervous system’s fightor-flight response to stress. This area receives input from the hypothalamus, amygdala and raphe nucleus among other regions and projects widely across the brain as well as to the spinal cord.2
Raphe Nucleus The raphe nucleus is an area located in the pons of the brainstem that is the principal site of the synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation, particularly when stress is associated with depression and anxiety.2
Spinal Cord The spinal cord transfer stress response neural impulses from the brain to the rest of the body. The neuroendocrine blood hormone signaling system initiated by the hypothalamus, the spinal cord communicates with the rest of the body by stimulating the peripheral nervous system. Certain nerves that belong to the sympathetic branch of the central nervous system exit the spinal cord and stimulate peripheral nerves, which in turn engage the body’s major organs and muscles in a fight-or-flight manner.2
Pituitary Gland The pituitary gland known as master gland, a small organ is located at the base of the brain just under the hypothalamus. This gland releases various hormones that play significant roles in regulating homeostasis. During a stress response, the pituitary gland releases hormones into the blood stream, called adrenocorticotropic hormone, which modulates a heavily regulated stress response system.2
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Dwivedi MK et al.
J. Adv. Res. Ayur. Yoga Unani Sidd. Homeo. 2015; 2(3)
Adrenal Gland
system’s sympathetic branch that prepares the body for fight-or-flight response.2
The adrenal gland is a major organ of the endocrine system that is located directly on top of the kidneys and is chiefly responsible for the synthesis of stress hormones that are released into the blood stream during a stress response. Cortisol is the major stress hormone released by the adrenal gland. In addition to the locus coeruleus existing as a source of the neurotransmitter norepinephrine within the central nervous system, the adrenal gland can also release norepinephrine during a stress response into the body’s blood stream, at this point epinephrine acts as a hormone in the endocrine system.2
Corticotrophin-Releasing Hormone Corticotrophin-releasing hormone is the neuro hormone secreted by the hypothalamus during a stress response that stimulates the anterior lobe of the pituitary gland by binding to its corticotropin-releasing hormonereceptors, causing the anterior pituitary to release adrenocorticotropic hormone.2
Adrenocorticotropic Hormone Adrenocorticotropic hormone is the hormone secreted by the anterior lobe of the pituitary gland into the body’s blood stream that stimulates the cortex of the adrenal gland by binding to its adrenocorticotropic hormone-receptors, thus causing the adrenal gland to release cortisol.2
Cortisol Cortisol is a steroid hormone, belonging to a broader class of steroids called glucocorticoids, produced by the adrenal gland and secreted during a stress response. Its primary function is to redistribute energy (glucose) to regions of the body that need it most (i.e., the brain and major muscles during a fight-or-flight situation). As a part of the body’s fight-or-flight response, cortisol also acts to suppress the body’s immune system. Cortisol is synthesized from cholesterol in the adrenal cortex. Its primary function is to increase blood sugar through gluconeogenesis, suppress the immune system and aid in fat and protein metabolism.2
Norepinephrine Norepinephrine is a neurotransmitter released from locus coeruleus when stimulated by the hypothalamus during a stress response. Norepinephrine serves as the primary chemical messenger of the central nervous
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Serotonin Serotonin is a neurotransmitter synthesized in the raphe nucleus of the pons of the brainstem and projects to most brain areas. Serotonin is thought to play an important role in mood regulation. Stress-induced serotonin dysfunctions have been associated with anxiety, fear and depression-like symptoms.2
Neuropeptide Y Neuropeptide Y is a protein that is synthesized in the hypothalamus and acts as a chemical messenger in the brain. Traditionally, it has been thought to play an important role in appetite, feeding behavior, and satiety, but more recent findings have implicated Neuropeptide Y in anxiety and stress, specifically, stress resiliency.2
Automatic Nervous System Autonomic Nervous System consists of the sympathetic (arousal) and parasympathetic nervous systems. The Central Nervous System performs the involuntary functions such as breathing and heart rate are programmed to function automatically. The sympathetic nervous system triggers the fight or flight response when there is a threat perceived by the organism. The sympathetic nervous system releases the hormones called catecholamines specifically epinephrine (adrenaline) and norepinephrine (noradrenaline) prepare the body for rapid metabolic function. The secretion of epinephrine and norepinephrine causes the acceleration of heart rate, vascodilation of arteries throughout working muscles. The parasympathetic calms the body through the parasympathetic response.1
Endocrine System The Endocrine system consists of a series of glands located throughout the body that regulate metabolic functions requiring endurance rather than speed. The endocrine system is a network of four components: glands, hormones, circulation and target organs. Endocrine glands manufacture and release biochemical substances called hormones. Hormones are chemical messengers made up of protein compounds that are programmed to attach to specific cell receptor sites to increase or decrease cell metabolism. Hormones are transported through the bloodstream from the glands that produced them to the
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target organs. The glands which are closely involved with the stress response are the pituitary, thyroid and adrenal glands. The pituitary gland called the master gland because it manufactures several important hormones.1
Serotonin A neurotransmitter is associated with mood. When a level of serotonin decreases, it leads to take shape of depression. Serotonin levels are affected by factors like stress hormones and the foods consumed.2
Hypothalamus Hypothalamus is associated with emotional processing. When someone perceives threats, the hypothalamus is activated and secretes corticotrophin- releasing factor (CRF) to the pituitary gland to stimulate the fight-or flight response.1
The ACTH Axis The hypothalamic- pituitary-adrenal (HPA) axis also known as ACTH axis begins with the release of corticotrophin releasing factor (CRF) from the anterior hypothalamus. This substance activates the pituitary gland to release ACTH, which travels via the bloodstream activate adrenal cortex. The adrenal cortex releases a set of corticosteroids (cortisol and aldosterone) which increases metabolism and alter body fluids and thus blood pressure, respectively.1
Cortisol The other stress hormone, cortisol, is present in the body all the time, but levels increase in response to danger and stress. In the short-term, its effects are positive, to help you deal with an immediate crisis, but long term stress means that cortisol builds up and creates a number of stress related health problems. Short-term positive effects are a quick burst of energy, decreased sensitivity to pain, increase in immunity, heightened memory. Long-term negative effects include imbalances of blood sugar, increase in abdominal fat storage, suppressed thyroid activity, decreased bone density, decreased muscle mass, high blood pressure, lowered immunity and less able to think clearly.4
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Body Reaction to Stress The body’s response to stress having symptoms of fast shallow breathing, headaches, constant tiredness, restlessness, sleeping problems, tendency to sweat, nervous twitches, cramps or muscle spasms, pins and needles, high blood pressure, feeling sick or dizzy, constipation or diarrhea, craving for food, indigestion or heartburn, lack of appetite, sexual difficulties, fainting, chest pains and grinding the teeth at night etc.4
Behavioral and Cognitive Symptoms of Stress Irritable, aggressive, depressed, fearing failure, dreading the future, a loss of interest in others, taking no interest in life, neglected, that there's no-one to confide in a loss of sense of humor, bad or ugly, fearful of seriously ill etc. This may result in finding it difficult to make decisions, finding it difficult to concentrate, denying there's a problem, avoiding difficult situations, frequently crying, biting your nails, unable to show your true feelings, being very snappy or aggressive and finding it difficult to talk to others etc.5
Conclusion The prolonged stress have a harmful effects on the body affecting various parts of the brain brings change in behavior and having physiological, cognitive and emotional effect on the various parts of the body. Longterm exposure to stress can lead to serious health problems. Chronic stress disrupts nearly every system in the body. It can raise blood pressure, suppress the immune system, increase the risk of heart attack and stroke, contribute to infertility, and speed up the aging process. Long-term stress can even rewire the brain leads to anxiety and depression. There is a variation in the body system due to which the different person respond differently to the stressful situations. As a result it may affect different body parts causes various diseases and illness.
References 1. Brian SL. Managing Stress: Principles and Strategies for Health and Well Being, 7th Ed. Burlington, MA: Jones & Bartlett Learning, 2012: 46-60. 2. Stress (biology). Available from: http:// en.m.wikipedia.org/wiki/stress. 3. Khokhar PC. Stress Coping and Management, 1st Ed. Meerut: Shalabh Publishing House, 2003: 56. 4. Darton K. How to manage stress. Mind (NAMH), 2012: 6.
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