Lecture+23+Stress - Stress A process: Interaction between...

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1 Stress A process: Interaction between environmental factors that reduce well-being (stressors) and the physiological response (stress response) Acute - fight or flight response Chronic - long term physiological adaptation, even to minor stressors Response to stressors is mediated by complex physiological, social, environmental and genetic factors Goal = consistent internal environment (homeostasis) 3 Physiological Systems Hypothalamic-pituitary-adrenal (HPA) axis Neural control of the endocrine system Hypothalamus controls the pituitary, which in turn controls hormonal release. The hypothalamus also directly releases hormones into the circulation Autonomic nervous system Sympathetic and parasympathetic system Neural control of organs (heart rate, blood vessels, GI tract, bladder, liver, pancreas) Also controlled by hypothalamus Immune system interactions between brain and immune response
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2 Autonomic Nervous System HPA Axis Circulation of hormones that regulate the endocrine system: adrenal gland - adrenocorticotrophin (ACTH regulates cortisol), thyroid - Thyrotropin (TRH, regulates thyroid hormone), etc. Peptides (oxytocin, vasopressin) secreted directly into circulation Releasing, and release- inhibiting substances regulate secretion of hormones from the pituitary: Corticotrophin-releasing hormone (CRF), thryrotropin releasing hormone (TRH), etc Wide range of neural input to the hypothalamus
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3 Mediators of Stress Response Catecholamines Secreted by sympathetic nervous system and adrenal medulla Increase heart rate, blood pressure, promote conversion of glycogen to glucose Glucocorticoids Secreted by adrenal cortex Increase blood glucose, appetite, food-seeking Antagonize action of insulin - this results in a feedback cycle that increases insulin release diabetes Increases central (abdominal) body fat/obesity Behavioral and Physiological Responses Acute Increased heart rate, perspiration, dry mouth Release of epinephrine (autonomic, adrenals) Release of cortisol (adrenals) Chronic Fatigue, irritability, hostility, demoralization Cortisol, catecholamines (epineprhine etc) Both Increased blood glucose, blood pressure, abdominal fat
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Lecture+23+Stress - Stress A process: Interaction between...

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