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Managing Stress 8E Principles and Strategies for Health and Well-Being Unless otherwise noted, all images were supplied by Brian Luke Seaward. Credit: © Inspiration Unlimited. Used with permission. Brian Luke Seaward, Ph.D. Chapter 3 Physiology of Stress Image © National Cancer Institute/Photodisc/Getty Images “To understand the stress response, we must possess a fundamental knowledge not only of psychology but physiology as well.” — George Everly Quotation reproduced from Everly Jr. et al. The Nature and Treatment of the Stress Response. 1981; with kind permission from Springer Science+Business Media B.V. Once the brain has interpreted some sensory information as a serious threat, the body goes into action for the purposes of survival. Once the brain has interpreted some sensory information as a serious threat, the body goes into action for the purposes of survival. Through a chain-command of neural and hormonal events, the body prepares to fight or flee…beginning with the central nervous system. Once the brain has interpreted some sensory information as a serious threat, the body goes into action for the purposes of survival. Through a chain-command of neural and hormonal events, the body prepares to fight or flee…beginning with the central nervous system. The term “psychophysiology” refers to this mind-body connection. The Central Nervous System The Central Nervous System The Central Nervous System (CNS) consists of the brain and spinal column while the peripheral nervous system (PNS) comprises all neural pathways to the extremities. The Central Nervous System • The Neocortical Level (The conscious power to override the stress response is here) The Central Nervous System • The Neocortical Level (The conscious power to override the stress response is here) • The Limbic System (Fight or flight is activated here!) The Central Nervous System • The Neocortical Level (The conscious power to override the stress response is here) • The Limbic System (Fight or flight is activated here!) • The Vegetative Level Figure 3.1. The three levels of the human brain include the vegetative level, the limbic system, and the neocortical level. © Bradford Veley, Marquette, MI The Autonomic Nervous System Sympathetic Nervous System (Stress Response) Parasympathetic Nervous System (Relaxation Response) The Autonomic Nervous System Sympathetic Nervous System (Stress Response) Parasympathetic Nervous System (Relaxation response) Epinephrine Norepinephrine Acetylcholine Figure 3.3. The sympathetic and parasympathetic nervous systems. Internal organs are typically innervated by neural fibers from both sympathetic and parasympathetic divisions. The Endocrine System The Endocrine System The endocrine system is made of many hormonal glands. Stress triggers the pituitary, hypothalamus, and adrenal glands. The adrenal gland is often called the stress gland for its role in the fight-or-flight response. Figure 3.5. The adrenal glands sit on top of each of the kidneys and are cone-shaped in appearance. The Adrenal Gland The Adrenal Gland The adrenal gland has two parts; the medulla and cortex. The medulla releases epinephrine and norepinephrine. The cortex releases corticosteroids (e.g., cortisol) which then help prepare the body’s energy production for flight or flight. Figure 3.4. The physiological response to stress. The Neuroendocrine Pathway 1. The ACTH Axis 2. The Vasopressin Axis 3. The Thyroxine Axis The Neuroendocrine Pathway 1. The ACTH Axis (also known as the HPA axis) • Corticotropin Releasing Factor (CRF) is released from the anterior hypothalamus • Pituitary gland then releases ACTH • ACTH travels via the bloodstream to the adrenal gland (cortex) • Adrenal cortex releases corticosteroids Figure 3.6. The ACTH Axis. The Neuroendocrine Pathway 2. The Vasopressin Axis • Vasopressin is also known as Antiduretic Hormone (ADH) • Vasopressin is synthesized in the hypothalamus but is released via the pituitary • Acts to increase water reabsorption and decrease perspiration for increased blood volume The Neuroendocrine Pathway 3. The Thyroxine Axis • Hypothalamus triggers release of thyrotropic hormone-releasing factor (TRF) to pituitary. • Pituitary then stimulates release of thyrotropic hormone (TTH) to the thyroid • TTH allows the thyroid to release thyroxine and triiodothryonine to increase metabolism. Table 3.1. Pathways of the Stress Response The Myth of Multitasking Insomnia and Brain Physiology A Parable of Psychophysiology A Parable of Psychophysiology (Your body has several physiological dynamics to ensure your physical survival) Figure 3.7. The immediate, intermediate, and prolonged effects of the stress response. A Decade of Brain Research A Decade of Brain Research • The hippocampus and amygdala together form conscious emotional memories A Decade of Brain Research • The hippocampus and amygdala together form conscious emotional memories • The hippocampus is highly sensitive to cortisol which aids in the memory function of stress A Decade of Brain Research • The hippocampus and amygdala together form conscious emotional memories • The hippocampus is highly sensitive to cortisol which aids in the memory function of stress • The hippocampus region is rich in receptor sites for glucocorticoids A Decade of Brain Research • The amygdala is associated with fear-based memories A Decade of Brain Research • The amygdala is associated with fear-based memories • Repeated exposure to cortisol accelerates the aging process of the brain and may shrink brain cells A Decade of Brain Research • The amygdala is associated with fear-based memories • Repeated exposure to cortisol accelerates the aging process of the brain and may shrink brain cells • Brain cells damaged via emotional stress appear to be irreversible A Decade of Brain Research • Neuroplasticity: The brain’s ability to generate new connections to various brains cells AND generate new cell growth (which was previously thought to be impossible!) A Decade of Brain Research • Neuroplasticity: The brain’s ability to generate new connections to various brains cells AND generate new cell growth (which was previously thought to be impossible!) • Relaxation techniques (e.g., meditation) are believed to promote neuroplasticity. Stress Physiology: Take Home Message Stress Physiology: Take Home Message • The stress response involves a cascade of stress hormones throughout the body. Stress Physiology: Take Home Message • The stress response involves a cascade of stress hormones throughout the body. • Cortisol plays a huge role in the stress response. Stress Physiology: Take Home Message • The stress response involves a cascade of stress hormones throughout the body. • Cortisol plays a huge role in the stress response. • The strength of the “stress-hormone cocktail” depends on the intensity and duration of stress. Stress Physiology: Take Home Message • The stress response involves a cascade of stress hormones throughout the body. • Cortisol plays a huge role in the stress response. • The strength of the “stress-hormone cocktail” depends on the intensity and duration of stress. • Repeated (chronic) stress shrinks (atrophies) brain cells.