Transcript Fight-or-Flight: The Peripheral Nervous System

Chapter 5
The Physical Basis of
Stress
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Overview
 This chapter
Provides an overview of the physical
basis of stress through an in-depth
analysis of Selye’s general adaptation
syndrome (GAS)
Describes how the GAS responds to
immediate and longer-term threats
Ends with a critical analysis of Selye’s
work based on recent studies
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Outline
Overview of the major body systems
involved in the stress response
Fight-or-flight: An alarm reaction
Resistance: A chronic, long-term stress
response
The physiology of exhaustion
A critical look at general adaptation
syndrome (GAS)
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Major Body Systems Involved in
the Stress Response
Communication, control, and
integration
The endocrine system
The nervous system
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Other Major Body Systems
Involved in the Stress Response
Transportation and defense
Cardiovascular
(circulatory) system
Immune system
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Other Major Body Systems
Involved in the Stress Response
Support and Movement
Muscular system
Respiration, Nutrition, and
Excretion
Gas exchange: The respiratory
system
Nutrition and excretion: The
digestive system
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
The Nervous System and Fight-orFlight (An Alarm Reation)
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 that
continue to exact a toll on our bodies
until we remove or cope with the
stressor that initiates is
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Axes and Pathways
 Everly and Lating use these terms to describe
the routes traveled through the body after a
potential stressor is appraised as threatening
 Three different pathways
The neural axis
The neuroendocrine axis (a.k.a. the
sympathoadrenomedullary system, or SAM)
The endocrine axis (contains the hypothalamicpituitary-adrenal-cortical system, or HPAC)
 The axes expand on Selye’s work
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
The Neural Axis
The central nervous system:
brain and spinal column
The peripheral nervous system:
all the other nerve pathways
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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
The diencephalon—forms the central
brain core and receives and routes messages
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Fight-or-Flight: The Brain
(continued)
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)
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Fight-or-Flight: The Spinal Cord
The lifeline between the brain
and the rest of the body
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Fight-or-Flight: The Peripheral
Nervous System
The somatic nervous system
Transmits messages under our conscious
control
The autonomic nervous system
Controls functions that are unconscious
Sympathetic branch: activates stress
responses
Parasympathetic branch: deactivates
stress responses (activates relaxation
responses)
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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)
Norepinephrine (noradrenaline)
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Resistance: A Continuous, LongTerm 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
The endocrine axes: adrenocortical,
somatotropic, thyroid, and pituitary systems
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Resistance—The Limbic System
Interacts with the cortex as our
emotions interact with our
thoughts
Prolongs or reduces the stress
response
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Resistance—The Endocrine System
The pituitary is known as the
master gland
All activities are orchestrated by
the pituitary gland through the
hypothalamus
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
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
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
General Adaptation Syndrome (GAS)
(A Review)
Developed by Selye, GAS has
three distinguishable phases
Alarm
Resistance
Exhaustion
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
A Critical Look at GAS
Two major challenges in recent years
Nonspecificity—Goldstein
Identified different responses to seven
specific stressors: water deprivation, salt
deprivation, posture changes, eating a large
meal, exercise, hemorrhage, and temperature
alteration
Eustress—Mason and
Frankenhauser
Found body response to threat different
from body response to challenge
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images
Chapter 5: The Physical Basis
of Stress
Summary
© 2007 McGraw-Hill Higher Education. All rights reserved.
Akira Kaede/Getty Images