Chapter 5
The Physical Basis of
Stress
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McGraw-Hill/Irwin
Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.
Major Body Systems Involved
in the Stress Response
 The endocrine system
 The nervous system:
 Communication
 Control
 Integration
 Cardiovascular (circulatory) system
 Transportation (sugars, salts, fats and oxygen)
 Immune system
 Defense - compromised
 Muscular system
 Support and Movement – muscle tension
 The respiratory system
 Gas exchange
 The digestive system
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 Nutrition and excretion
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General Adaptation
Syndrome (GAS):
A Review
Developed by Selye, GAS has
three distinguishable phases
Alarm – fight or flight
Resistance – idling too fast
Exhaustion – tank goes empty
Problems?
Non-specificity
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The Nervous System and
Fight-or-Flight (An Alarm
Reaction)
Fight-or-flight stress response helps
us get out of harm’s way
Selye’s General Adaptation
Syndrome (GAS) alarm phase
Stress response: a series of phases
(ARE) that continue to exact a toll
on our bodies until we remove or
cope with the stressor that initiates it
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Axes and Pathways
 Everly & Lating: Three different pathways
The neural axis
The neuroendocrine axis (a.k.a. the
sympathoadrenomedullary system, or SAM)
The endocrine axis (contains the
hypothalamic-pituitary-adrenal-cortical
system, or HPAC)
 The axes expand on Selye’s work
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The Neural Axis (aka
neural networks)
 Central Nervous System (CNS): Brain and
spinal cord
 Peripheral Nervous System: All parts of the
nervous system outside of the brain and
spinal cord
 Somatic System: Links spinal cord with body and
sense organs; controls voluntary behavior
 Autonomic System: Serves internal organs and
glands; controls automatic functions such as heart
rate and blood pressure
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 Sympathetic: Arouses body; emergency
system
 Parasympathetic: Quiets body;
most active after an emotional event
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Fight-or-Flight: The
Brain
 The fight-or-flight response
Originates with the brain’s perception of
threat
 Different parts of the brain are involved in
the stress response
The cerebral cortex—covers the
cerebrum and controls higher thought
processes
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The diencephalon—forms the central
brain core and receives and routes
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messages (thalamus and hypothalamus)
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Fight-or-Flight: The Brain
(continued)
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The limbic system
Links the emotional brain with the
thinking, rational brain
The brain stem
Produces autonomic functions
(necessary for survival)
Is pathway for both general and
specific cortical arousal through the
reticular activating system (RAS)
 The spinal cord
The lifeline between the brain and
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the rest of the body
Figure 2.26
FIGURE 2.26 Parts of the limbic system. Although only one side is shown here, the hippocampus
and the amygdala extend out into the temporal lobes at each side of the brain. The limbic system
is a sort of “primitive core” of the brain strongly associated with emotion.
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Fight-or-Flight: The
Peripheral Nervous System
The somatic nervous system
Transmits messages under our
conscious control (Run, Fight)
The autonomic nervous system
Controls functions that are unconscious
Sympathetic branch: activates stress
responses
Parasympathetic branch: deactivates
stress responses (activates relaxation
responses)
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Fight-or-Flight: The
Endocrine System of the
Neuroendocrine Axis
Produces hormones associated
with alarm
Adrenal glands play the most
significant role in the stress
response
Epinephrine (adrenaline - fear)
Norepinephrine (noradrenaline
- anger)
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Resistance: A Continuous,
Long-Term Stress Response
 The physiology of resistance: The body
not at rest but also not in the throes of
alarm
 Roles played by
The brain: the cerebral cortex,
diencephalon, limbic system, and brain stem
(identifies stress issues and sends messages to
the body to prepare for action)
The endocrine axes: adrenocortical,
somatotropic, thyroid, and pituitary systems
(responds to the brain to prepare the body to
act)
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Resistance—The
Cerebral Cortex
The cerebral cortex—the key
part of the brain involved in
resistance
Our thoughts about stressors,
especially illogical thoughts, keep
them alive or allow them to
dissipate
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Resistance—The Limbic
System
Interacts with the cortex as our
emotions interact with our
thoughts
Prolongs or reduces the stress
response
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Resistance—The Endocrine
System
The pituitary is known as the
master gland
All activities are orchestrated by
the pituitary gland through the
hypothalamus
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Resistance—The Adrenal
Function
The medulla secretes two key
groups of hormones
Gluccocorticoids (sugars)
Cortisol provides energy, reduces
inflammation, prolongs stress
response
Mineralocorticoids (salts)
Aldosterone keeps blood pressure
elevated
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The Physiology of
Exhaustion
Selye believed all living things
have a finite amount of energy
to adapt to stress
When that is used up, one
suffers exhaustion
Organisms vary in how they
become exhausted
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Exhaustion—The Weak
Link
Selye asserted all living things
have a “weak link,” the first
part to fail
Chronic stress puts a heavy
demand on strategic body parts
Heart, blood vessels, and
adrenal and thyroid glands are
most susceptible
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