Fight or flight: Flashcards
Fight or flight response:
The body’s physiological reactions to threat or danger, involved activation of the hypothalamic-pirtuitary-adrenal cortex pathways and the sympathetic-adrenal-medullary system; designed to provide energy and arousal for rapid responses to threat and danger
Fight or flight: information
-HPA and SAM activation results in high blood levels of glucose and fats such as, triglycerides, along with an increased heart rate and blood pressure
-in the case of animals, these energy reserves are burnt up in muscle activity and, once it has escaped, blood levels return to normal and blood pressure and heart rate fall
-for modern humans, we experience major life stressors, for example, exams, relationships, redundancy, and bereavement, these stressors are equally as effective in activating the HPA and SAM system
-the response to such stressors does not usually require a huge energy expenditure, even though our bloodstream is flooded with glucose and fats
-it is the negative effects of this high level of bodily arousal that have been associated with stress-related illnesses
-the body’s fight or flight response begins with appraisal of the situation, followed by the activation of the two key pathways
Appraisal:
-appraisal or evaluation of the situation depends upon the sensory processing systems, such as vision and hearing, and stored memories of previous encounters with the situation
-key structures in the brain include higher cortical centres and parts of the limbic system, especially those involved with emotional memory such as amygdala and hippocampus
-if the situation is appraised as potentially dangerous, the hypothalamus at the base of the brain is alerted
-they hypothalamus controls to major systems that have central roles in bodily arousal, the hypothalamic-pirtuitary-adrenal axis (HPA) and the sympathetic adrenomdedullary (SAM) pathway
The hypothalamic-pirtuitary-adrenal axis (HPA):
-the pirtuitary gland sits just beneath the brain, connected to the hypothalamus by a short stalk, the pirtuitary is the master gland of the body, releasing a number of hormones into the bloodstream
-they key pirtuitary stress hormone is adrenocortitropic hormone (ACTH)
-the hypothalamus stimulates the release of ACTH from the anterior pirtuitary into the bloodstream
-the hormone travels to the adrenal cortex, part of the adrenal gland (we have 2 adrenal glands, located close to the kidney on each side of the body)
-when ACTH reaches the adrenal cortex, it stimulates the release of glucorcoticoids, especially those such as cortisol and corticosterone, into the bloodstream
-these hormones, in turn, have a major effect on the body
the sympathetic adrenomedullary pathway (SAM):
-the sympathetic nervous system (SNS) is one part of the automatic nervous system that controls our internal organs
-nerve pathways of the SNS originate in the brainstem and travel via the spinal cord and spinal nerves to the various body organs
-one of these pathways runs to the adrenal medulla, which along with the adrenal cortex makes up the adrenal gland
-when appraisal processes in higher brain centres detect a stressful situation, the hypthalamus is instructed to stimulate ACTH release from the pirtuiry
-in addition, the hypothalamus also activates the SNS centres in the brainstem and the pathways running to the adrenal medulla (SAM pathway)
-this results in the increased release of adrenaline and noradrenaline into the bloodstream
role of hormes in fight or flight:
-the hormones that are flooded into the bloodstream following a dangerous and stressful situation have a number of effects on the body, mainly designed to provide for energy expenditure used in responses to stress, such as confrontation or escape
-the SNS itself 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, to a lesser extent, noradrenaline from the adrenal medulla via the SAM pathway
-adrenaline in particular acts on the heart muscles to increase the heart rate, and also on blood vessels to constrict them and so raise blood pressure
-the end result is that oxygen is rapidly bumped to the muscles of the skeleton, allowing for increased physical activity
the role of hormones in the fight or flight response 2.0:
-the body’s energy are largely in the form of glycogen stored in the liver and fat reserves in fatty tissue
-a major effect of circulating adrenaline released in response to SAM is the increased release or mobilisation of these energy reserves; this in the form or raised blood levels of glucose (from glycogen) and fatty acids such as triglycerides (from our fat reserves)
-raised levels of corticosteroids, if sustained over a long period, also have the interesting effect of supressing the body’s immune system
-this system is the body’s defensw against infection, and cosists of a variety of complex subsystems vital in keeping the person healthy
stress-related illness:
-it is now thought that stress-related illnesses are not cause by exhaustion of the body’s physiological stress response, but rather it is the effect of chronic or long-term raised levels of stress hormones that evenatually lead to illness
-long-term raised levels of sugars and fats in the bloodstream, these can contribute to the furring-up and narrowing of blood vessels, known as astherosclerosis
-the effects of adrenaline and noradrenaline in raising heart rate and blood pressure, this can physicially damage blood vessels in the long term, by eroding the lining of blood vessels and causing hermorrhages where the lining of blood vessels is weakened
-long-term raised levels of corticosteroids, these supress the body’s immune system + leaves us vulnerable to infections and disease
