{ Stress: The body’s response to stress

 The body's response to stress begins with appraisal (assessing) of the situation, followed by activation of two key pathways:  Primary + Secondary appraisal(assessing) depends on the sensory processing systems such as vision, hearing, and sorted memories of previous encounters of the situation  If the situation is appraised as potentially stressful, the hypothalamus at the base of the brain is alerted. The hypothalamus control’s two major systems that have central roles in the body's response to stressors, the pituitary adrenal system axis and the sympathomedullary pathway. Appraisal

Pituitary-adrenal system and sympathomedullary pathway Higher brain centres (cortex and limbic systems) Appraisal of threat/coping resources involves the cortex and parts of the limbic systems Pituitary Gland: Master of the body, below the brain in the cranial cavity, controlled by the hypothalamus. The PG releases hormones and controls the activity of other glands in the body. Hypothalamus Brainstem autonomic centres Pituitary gland Adrenal cortex Adrenal medulla Adrenaline and noradrenaline in bloodstream Physiological effects on body Corticosteroids in bloodstream

 The pituitary gland sits beneath the brain connected to the hypothalamus by a short stalk known as the infundibulum.  The pituitary gland is the master of the body, releasing a number of hormones into the bloodstream.  A major function of these hormones is to control other glands spread around the body involved in vital functions such as reproduction and growth.  Ultimate control of these hormones is located in the hypothalamus and their release depends upon hypothalamic activity. Pituitary-adrenal System

 The key pituitary stress hormone is adrenocorticotrophic hormone. (ACTH) Which is a hormone released by the pituitary gland, ACTH stimulates the adrenal cortex to release corticosteroids as part of the body's response to stress.  The hormone travels to the adrenal cortex which is part of the adrenal gland. (Adrenal cortex - Is part of the adrenal gland, it releases corticosteroids into the bloodstream as a response to stress) (Adrenal gland - Two adrenal glands located just by the kidneys, made up of the cortex and medulla, cortex releases corticosteroids, the medulla releases adrenaline and noradrenaline.)  When ACTH reaches the adrenal cortex it stimulates the release of corticosteroids (hormones released from the adrenal cortex as part of stress response) such as cortisol and corticosteroids into the bloodstream. Pituitary-adrenal System

 The sympathetic nervous system (SNS) is one part of the autonomic nervous system, that control’s our internal organs, such as various glands, the heart, and the circulation system and the digestive system.  Nerve pathways of the SNS originate in the brain-stem (part of the brain just above the spinal cord) and travel via the spinal cord and spinal nerves to various body organs.  One of these pathways runs to the adrenal medulla (releases noradrenaline and adrenaline into the bloodstream as a stress response), which along with the adrenal cortex makes up the adrenal gland.  When activated the SNS stimulates the adrenal medulla to release the hormones adrenaline (hormone released from the adrenal medulla, increases heart rate and blood pressure) and noradrenaline into the bloodstream. The sympathomedullary pathway

 The ANS functions to control our internal organs automatically without out conscious control, and plays a vital role in stress responses.  When appraisal processes in higher brain centres detect a stressful situation, the hypothalamus is instructed to stimulate ACTH release from the pituitary.  When appraisal processes in higher brain centres detect a stressful situation, the hypothalamus is instructed to stimulate ACTH release from the pituitary.  The hypothalamus also commands the adrenal medulla (sympathomedullary pathway)  This then increases the release of adrenaline and noradrenaline into the bloodstream. The sympathomedullary pathway

 The SNS has direct connections to the heart and activation speeds up heart rate and raises blood pressure. These effects are increased and sustained by the release of adrenaline and noradrenaline.  The body's energy reserves are largely in the form of glycogen stored in the liver and fat reserves in fatty tissues. A major effect of the corticosteroids released in response to the pituitary-adrenal system activation is the increased release or mobilisation of these energy reserves.  Raised levels of corticosteroids, if sustained over a long period, also have the interesting effect of suppressing the body's immune system. The sympathomedullary pathway

 Selye (on the basis of his studies of rats) developed a three stage model of how the body responds to stressors:  Stage 1: Alarm  A stressor is perceived and the pituitary-adrenal system and the sympathomedullary pathway are activated.  Levels of stress-related hormones surge, heart-rate and blood pressure increase and energy reserves are mobilised.  Stage 2: Resistance  If the stressor persists the body's response systems maintain their activation, with levels of stress-related hormones and bodily arousal reserves are mobilised.  Stage 3: Exhaustion  Chronic stress (long periods of stress) eventually exhaust the body's defense systems and it's ability to maintain high levels of circulating stress hormones. This is the stage when stress- related illness may develop. Selye’s General Adaptation Syndrome

 Selye's work has been highly influential in developing the whole area of research into stress. He emphasised the components of the brain which relate to stress.  Selye emphasised that the GAS (general adaption syndrome - Selye's model of the body's response to stress) was a common response to all stressors.  It is now thought that stress-related illnesses are not caused by exhaustion of the body's physiological stress responses. Rather, it is the effect of chronic/long lasting levels of stress hormones that can eventually lead to illness. Selye’s General Adaptation Syndrome: Evaluation