The body's responses to stress

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  • Created on: 11-01-13 07:36
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The body's response to stress:
1. Acute stress ­ sympathomedullary pathway
2. Chronic stress ­ pituitary-adrenal system
Acute stress ­ sympathomedullary pathway:
The influence of the SNS and adrenal medulla prepares the body for fight or
flight when faced with an acute stressor. The sympathomedullary pathway
is made up of the sympathetic adrenal medullary system (SAM) and the
Sympathetic nervous system (SNS).
SAM, this releases adrenaline into the body when the SNS is activated
getting the body ready for the fight or flight response, it is regulated by
the SNS and adrenal medulla
SNS, this is activated when the body is exposed to an acute stressor.
Noradrenaline is released by the body when the SNS is activated which
activates internal body organs to prepare them for the body's response
to the fight of flight, this leads to increased heart rate and metabolism
also increased pupil size.
Adrenal medulla, releases adrenaline when activated by the neurones
from the SNS. The adrenaline provides extra glucose and oxygen to the
brain and muscles, also suppressing non-emergency bodily processes such
as digestion.
Acute stressors activate the Autonomic nervous system (ANS), this is the
part of the nervous system which has automatic processes such as
breathing, the heart beating and digestion as they wouldn't work as well if
we had to think about doing them. This is divided into 2 branched the SNS and
PSNS (parasympathetic nervous system). The SNS arouses the body in the
presence of a stressor and the PSNS bring the body back into a calm and
relaxed state.
Chronic stress ­ pituitary-adrenal system
A stress response system, which helps the body deal with chronic stress.
HPA activated by both physical and emotional stressors but is much harder
to achieve in situations of ongoing stress. This system is also known as the
hypothalamatic-pituitary-adrenal axis (HPA). This system controls the level
of cortisol and other stress hormones in the body controlling chronic stress.
-Hypothalamus, this is the part of the brain which deal with hormones so
when a stressor is sensed by the brain a message is sent to the
hypothalamus which activates the production of a chemical messenger called
corticotrophin-releasing factor (CRF) which is released into the bloodstream.
-The pituitary gland, if the gland senses the presence of CRF in the
bloodstream it activated the production of adrenocorticotrophic hormone
(ACTH), this is released into the bloodstream heading for the adrenal
-The adrenal cortex, when ACTH reaches the adrenal glands it stimulates
the adrenal cortex to release cortisol, this provides the body with a quick
burst of energy and lower sensitivity to pain which are good effects but it
also causes higher blood pressure, impaired cognitive performance and
lowered immune response which are bad effects.
It usually takes 20 minutes for the process to occur, meaning this system
doesn't work well for acute stress; levels of cortisol only increase after 20

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The system is very effective at
regulating itself; the hypothalamus and pituitary glands have receptors that
sense if cortisol levels are too high or low in the body. If levels are too high
CRF and ACTH production is reduced bringing levels back to normal and if they
are too low production of CRH and ACTH are increased.…read more


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