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Chapter 3

PSYC23H3 Chapter Notes - Chapter 3: Glucocorticoid Receptor, Myelin Basic Protein, Adrenal Gland

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David Haley

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Excessive Stress Disrupts the Architecture of the Developing Brain
The Issue:
Extensive research on the biology of stress now shows that healthy development can be derailed by excessive or
prolonged activation of stress response systems in the body and the brain, with damaging effects on learning,
behavior, and health across the lifespan.
When faced with threatening situations, our bodies respond by increasing our heart rate, blood pressure, and stress
hormones, such as cortisol.
If a child has extreme stress response and buffering relationships aren’t available to the child, the result can be
toxic stress, leading to damaged, weakened bodily systems and brain architecture, with lifelong repercussions.
Not all stress is harmful stress response depends on: duration, intensity, and timing of the stressful experience
o Positive stress
moderate, short-lived stress responses
ex. brief increases in heart rate or mild changes in the body’s stress hormone levels/ challenge of
meeting new ppl for the child, getting immunizations, etc.
o Tolerable stress
stress responses that have the potential to negatively affect the architecture of the developing
brain but occur over long periods of time therefore giving the brain recovery time
ex. Death of a loved one
o Toxic stress
strong, frequent, or pro- longed activation of the body’s stress management system.
Stressful events that are chronic, uncontrollable, and/or experienced without children having
access to support from caring adults
Ex. Early abuse
What Science Tells Us:
Capacity to deal with stress is controlled by a set of interrelated brain circuits and hormone systems that are
specifically designed to respond to environmental changes.
The neural circuits for dealing with stress are particularly malleable (or “plastic”) during the fetal and early
childhood periods.
o Early exposure to toxic stress leads to poorly controlled stress response systems.
Well-functioning brain systems that respond to stress are essential to healthy development.
o Being able to cope with potentially threatening situations such as an unfamiliar environment or physical
danger is essential.
Frequent activation of brain systems that respond to stress can lead to vulnerability to a range of behavioral and
physiological disorders
Stress responses include activation of a variety of hormone and neurochemical systems throughout the body
o Two hormone systems that have received extensive attention are:
Sympathetic adrenomedullary (SAM) produced adrenaline in the central part of the
adrenal gland
Hypothalamic pituitary-adrenocortical (HPA) produces cortisol in the outer shell of the
adrenal gland.
o Bother adrenaline and cortisol are produced under normal circumstances and help prepare the body for
coping with stressors.
Adrenaline production occurs in response to many forms of acute stress
o Mobilizes energy stores and alters blood blow, thereby allowing the body to effectively deal with a range
of stresses.
Cortisol is produced in response to many forms of stress helps body cope with adverse situations
o Cortisol memory stores enhance certain types of memory and activate immune responses.
Sustained or frequent activation of hormonal systems can have negative impacts.
o Long term elevations in cortisol levels can alter the function of a number of neural systems, suppress the
immune response, and even change the architecture of regions in the brain that are important for learning
and memory.
Stress turns specific genes “on” and others “off” at particular times and locations in the brain and cortisol plays a
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