Psychophysiology of Stress

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Psychophysiology of Stress

• the bodys physiological reaction to perceived
  stressors... enhanced or mitigated by a complex
  of mind-body connections

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Theories of Brain Organization

• Reductionistic
• e.g., phrenology (brain localization)
• Integrative
• e.g., neocortical (hierarchical) override

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Phrenology(Franz Gall, Orson Lorenzo Fowler)

• Brain is the organ of the mind
• Brain is divided into areas responsible for
  specific characteristics
• Brain mass is proportional to the extent of
  characteristics
• Bumps develop to accommodate brain mass

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Neocortical Override(Paul MacLean)

• Brain is organized into an interrelated hierarchy
  of structures (though some regions have
  autonomous responsibilities)
• Tools of discovery have included
• organic impairment and injury
• artificial stimulation
• split-brain experiments (Roger Sperry)

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Neocortical Override(Paul MacLean)

• Layers are added to the brain from lower animals
  (i.e., reptiles) to higher animals (i.e.,
  mammals).
• Vertical level (layer) dictates the complexity of
  brain activity.
• Each level has the capability to override the
  functioning of the levels below.
• Cerebral cortex is the neocortex.
• primary control ( 50 of all functions)
• capable of more control with training
• thought can regulate measurable physiologic
  activity

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Human Brain Levels
Neocortical Level (cerebral cortex)
Limbic Level (limbic system, visceral / motor
control)
Vegetative Level (brainstem)
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Revisiting the Psychosomatic Model
Stimulus
Perception
Cerebral Cortex
Thalamus (sensory)
Subthalamus (motor)
(survival)
Higher Limbic System
Lower Limbic System
Brainstem
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Stress Neuroendocrine Response

• Nervous System (neuro) sudden, acute visceral
  changes
• Endocrine System long-term visceral changes
• Stress Centers receive the primary focus
• hypothalamus
• pituitary
• adrenal glands

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Autonomic Nervous System Response(immediate)
Anterior Hypothalamus Calling!!

• SYMPATHETIC
• arousal increased system activity
• release of energy
• changes in body response
• fight-or-flight
• organ innervation from many nerves

• PARA-SYMPATHETIC
• calming decreased system activity
• conservation of energy
• steady, constant responses
• homeostasis
• organ innervation from 10th cranial (AKA vagus)
  nerve

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Direct Organ Innervation(hypothalamus ? ANS ?
receptors on organ)

• Activity of organ is dependent on
• inherent function of that specific organ
• sympathetic activity (usually stimulation)
• para-sympathetic activity (usually inhibition)
• Measurable changes within 2.5 seconds
• Catecholamines released by sympathetic system
• Acetylcholine released by para-sympathetic system
• 10 minute supply of catecholamines

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Reserve energy comes from adrenal glands...

• Manufactures and stores catecholamines
• Releases catecholamines when stimulated by the
  sympathetic nervous system
• Can you see a problem with this mechanism?
• Catecholamines secreted into the bloodstream
• reach end organs within 30 seconds
• no inhibition mechanism
• 60 minute supply of catecholamines

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Points of Interest

• Nervous system can shut down quickly when
  compared to the circulatory system
• Sympathetic innervation to the sweat glands and
  the adrenal medulla (only) uses acetylcholine
• No para-sympathetic innervation to adrenal
  medulla
• Few individuals respond to stress
  para-sympathetically

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Endocrine Response
Youve Got Mail!!!

• Hypo-hypophyseal Portal System
• integrated circulatory system
• nucleii of hypothalamus send nerve cells into
  portal system (releasing hormones / factors)
• releasing hormones stimulate trophic hormones
  from pituitary cells
• cell nucleii, releasing trophic hormones are
  all specific

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ACTH Axis Adenocorticotrophic Hormone

• Mineralcorticoids (aldosterone)
• regulate salt / fluid balance in the kidneys (K,
  Na)
• increase blood volume
• increase blood pressure
• Glucocorticoids (cortisol)
• initiate gluconeogenesis
• stimulate glycogenolysis
• perpetuate vasoconstriction / cardiac responses
• increase RBC number size
• initiate nocturnal release of peptic acids
• 2 min ? 4 hours (peak at 30 min)

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Thyroxine Axis

• Thyroxine / Growth Hormone
• repair cortisol damage
• elevate metabolic rate, including cardiac
  functions
• stimulate gastrointestinal activity
• increase cerebration
• 2 days ? peak at 10-14 days

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Vasopressin Axis

• ADH / Vasopressin
• produced in hypothalamus stored in pituitary
• released under strong stimuli only
• constricts blood vessels
• raises blood pressure
• retains water in kidneys-- increases blood volume
  and pressure