stress management : PHYSIOLOGY OF THE STRESS RESPONSE 2
The main sympathetic neurotransmitter is called noradrenaline which is released a the nerve endings. The stress response also includes the activity of the adrenal, pituitary and thyroid glands.
The two adrenal glands are located one on top of each kidney. The middle part of the adrenal gland is called the adrenal medulla and is connected to the sympathetic nervous system by nerves. Once the latter system is in action it instructs the adrenal medulla to produce adrenaline and noradrenaline (catecholamines) which are released into the blood supply. The adrenaline prepares the body for flight and the noradrenaline prepares the body for fight. They increase both the heart rate, and the pressure at which the blood leaves the heart; they dilate bronchial passages and dilate coronary arteries; skin blood vessels constrict and there is an increase in metabolic rate. Also gastrointestinal system activity reduces which leads to a sensation of butterflies in the stomach.
Lying close to the hypothalamus in the brain is an endocrine gland called the pituitary. In a stressful situation, the anterior hypothalamus activates the pituitary. The pituitary releases adrenocorticotrophic hormone (ACTH) into the blood which then activates the outer part of the adrenal gland, the adrenal cortex. This then synthesises cortisol which increases arterial blood pressure, mobilises fats and glucose from the adipose (fat) tissues, reduces allergic reactions, reduces inflammation and can decrease lymphocytes that are involved in dealing with invading particles or bacteria. Consequently, increased cortisol levels over a prolonged period of time lowers the efficiency of the immune system. The adrenal cortex releases aldosterone which increases blood volume and subsequently blood pressure. Unfortunately, prolonged arousal over a period of time due to stress can lead to essential hypertension.
The pituitary also releases thyroid stimulating hormone which stimulates the thyroid gland, which is located in the neck, to secrete thyroxin. Thyroxin increases the metabolic rate, raises blood sugar levels, increases respiration/heart rate/blood pressure/and intestinal motility. Increased intestinal motility can lead to diarrhoea. (It is worth noting that an over-active thyroid gland under normal circumstances can be a major contributory factor in anxiety attacks. This would normally require medication.)
The pituitary also releases oxytocin and vasopressin which contract smooth muscles such as the blood vessels. Oxytocin causes contraction of the uterus. Vasopressin increases the permeability of the vessels to water therefore increasing blood pressure. It can lead to contraction of the intestinal musculature.
If the person perceives that the threatening situation has passed then the parasympathetic nervous system helps to restore the person to a state of equilibrium. However, for many people they perceive everyday of their life as stressful. Unfortunately, the prolonged effect of the stress response is that the body's immune system is lowered and blood pressure is raised which may lead to essential hypertension and headaches. The adrenal gland may malfunction which can result in tiredness with the muscles feeling weak; digestive difficulties with a craving for sweet, starchy food; dizziness; and disturbances of sleep.
Below are some of the symptoms of stress. Please note that these symptoms can also occur with a range of medical or psychological disorders. When in doubt, do consult your doctor or consultant.
Copyright 2000, Stephen Palmer
The two adrenal glands are located one on top of each kidney. The middle part of the adrenal gland is called the adrenal medulla and is connected to the sympathetic nervous system by nerves. Once the latter system is in action it instructs the adrenal medulla to produce adrenaline and noradrenaline (catecholamines) which are released into the blood supply. The adrenaline prepares the body for flight and the noradrenaline prepares the body for fight. They increase both the heart rate, and the pressure at which the blood leaves the heart; they dilate bronchial passages and dilate coronary arteries; skin blood vessels constrict and there is an increase in metabolic rate. Also gastrointestinal system activity reduces which leads to a sensation of butterflies in the stomach.
Lying close to the hypothalamus in the brain is an endocrine gland called the pituitary. In a stressful situation, the anterior hypothalamus activates the pituitary. The pituitary releases adrenocorticotrophic hormone (ACTH) into the blood which then activates the outer part of the adrenal gland, the adrenal cortex. This then synthesises cortisol which increases arterial blood pressure, mobilises fats and glucose from the adipose (fat) tissues, reduces allergic reactions, reduces inflammation and can decrease lymphocytes that are involved in dealing with invading particles or bacteria. Consequently, increased cortisol levels over a prolonged period of time lowers the efficiency of the immune system. The adrenal cortex releases aldosterone which increases blood volume and subsequently blood pressure. Unfortunately, prolonged arousal over a period of time due to stress can lead to essential hypertension.
The pituitary also releases thyroid stimulating hormone which stimulates the thyroid gland, which is located in the neck, to secrete thyroxin. Thyroxin increases the metabolic rate, raises blood sugar levels, increases respiration/heart rate/blood pressure/and intestinal motility. Increased intestinal motility can lead to diarrhoea. (It is worth noting that an over-active thyroid gland under normal circumstances can be a major contributory factor in anxiety attacks. This would normally require medication.)
The pituitary also releases oxytocin and vasopressin which contract smooth muscles such as the blood vessels. Oxytocin causes contraction of the uterus. Vasopressin increases the permeability of the vessels to water therefore increasing blood pressure. It can lead to contraction of the intestinal musculature.
If the person perceives that the threatening situation has passed then the parasympathetic nervous system helps to restore the person to a state of equilibrium. However, for many people they perceive everyday of their life as stressful. Unfortunately, the prolonged effect of the stress response is that the body's immune system is lowered and blood pressure is raised which may lead to essential hypertension and headaches. The adrenal gland may malfunction which can result in tiredness with the muscles feeling weak; digestive difficulties with a craving for sweet, starchy food; dizziness; and disturbances of sleep.
Below are some of the symptoms of stress. Please note that these symptoms can also occur with a range of medical or psychological disorders. When in doubt, do consult your doctor or consultant.
Copyright 2000, Stephen Palmer
