The Cybernetics of Stress: Causes, Chemicals, Consequences

1
The Cybernetics of StressCauses, Chemicals,
Consequences

• Richard W. Fardy, M.Ed.
• Wilmington High School
• Wilmington, MA

2
Relevant National Standards

• Content Standard C
• As a result of their activities in grades 9-12,
  all
• students should develop an understanding of
• The cell
• Biological evolution
• Matter, energy, and organization of living
  systems
• Behavior of organisms

3
Relevant Standards from the Massachusetts
Curriculum Frameworks (Health)

• Standard 5
• Students will acquire knowledge about emotions
  and physical health,and will learn skills to
  promote self-acceptance, make decisions and cope
  with stress.

4
Relevant Standards from the Massachusetts
Curriculum Frameworks (Biology 9-10)

• Structure and Function of Cells
• 2.1 Relate cell parts/organelles to their
  functions.
• Human Anatomy and Physiology
• 4.2 Describe how the functions of individual
  systems within humans are integrated to maintain
  a homeostatic balance.
• Evolution and Biodiversity
• 5.1 Explain how comparative anatomyand other
  evidence support the theory of evolution.

5
Juggling and Authentic Learning

• A juggler must simultaneously integrate sensory
  and muscular circuitry to keep all the objects in
  the air.

Source http//office.microsoft.com/clipart
6
Juggling and Authentic Learning (cont.)

• In order for learning to be truly authentic,
  learning experiences need to show connections to
  real life.
• Events do not always occur in a series of
  compartmentalized and disconnected boxes but
  still maintain connections to one another in some
  way and manner.

7
Link to Learn

• The raison detre for both interdisciplinary
  instruction and conceptual linkage within a
  particular subject area

Source http//office.microsoft.com/clipart
8
Module Objectives

• To be able to explain what happens in the three
  stages of the general adaptation syndrome (GAS).
• To be able to identify the parts of a neuron and
  explain how neurons transmit messages.
• To be able to define cybernetics and its
  connection to the nervous and endocrine systems.
• To be able to define homeostasis, allostasis,and
  allostatic load, and explain the effects of
  stress on homeostatic equilibrium.

9
Module Objectives (continued)

• To be able to describe the essential components
  of a biological feedback loop and to explain the
  differences in the effects of negative and
  positive loops.
• To describe the psychological, neurological, and
  endocrine events that occur when anorexia nervosa
  results from stress.
• To be able to describe how population density
  induces stress in animals and the possible
  implications for humans.

10
Module Objectives (continued)

• To be able to explain the integration of the
  nervous and endocrine systems in the stress
  response.
• To describe the general anatomy of the brain
  based on a sheep brain dissection.
• To be able to explain how conditioning and
  learning may be accomplished in planaria and how
  stress may affect this process.

11
Ancient Proverb

• I hear and I forget.
• I see and I remember.
• I do and I understand.
• ?Confucius

Source www.ironordeal.com/clipart/per
sons/Confucius.htm.
12
Hans Selye (1907-1982)

• Proposed general adaptation syndrome (GAS)
• GAS theory first published in Nature in 1936
• Described as bodys adaptive response to stress

13
Just What Exactly Is Stress?

• Initially identified by Selye as noxious
  agents.
• Became known as stress syndrome.

Source www.alnoorhospital.com/uploadedfiles/comm
on/stress/jpg
14
Selyes Three Stages of Stress

• Stage 1 The alarm reaction in which the body
  prepares itself for fight or flight.
• Stage 2 Since the first stage cannot long be
  sustained, there is a general resistance to the
  stress which is established.
• Stage 3 If the stress is continued for a long
  period of time, then eventual exhaustion results
  (the bodys response to prolonged wear and
  tear).

15
Selyes Final Analysis

• Stress includes both internal and external
  factors.
• Factors involve the nonspecific response of the
  body to any demand."

16
The Fight or Flight Response

• Perceive extreme danger or distress
• Neurons (nerve cells) in brain send entire body
  into high gear
• Responsively prepare for fight or flight

Source www.saludparati.com/entres.htm
17
Selyes Third Stage

• Challenged by physiological, psychological, and
  environmental changes (stressors)
• Failure to accommodate to changes can lead to
  exhaustion

Source www.bet.com/Health/Archives
18
What Are Neurons?

• Neurons are the specialized cells of which nerve
  tissue is composed.
• Neurons have the ability to send messages to
  each other through the release of chemical
  substances called neurotransmitters.
• Neurons are also electrical in nature,
  maintaining polarity through electrical gradients
  established by ions on the inside and outside of
  their cell membranes.
• Neurons send electrical signals (action
  potentials) by depolarizing.

19
What Do Neurons Look Like?

• Nerve smear containing neuron, axon, dendrite,
  cell body, nucleus, and nucleolus
• Source http//facstaff.bloomu.edu/jhranitz/teachi
  ng/APHNT/Laboratory20Pictures.htm

20
Neurons labeled with fluorescent proteins
Source Joshua Sanes, Harvard University.
LectureNeurons how they look and what they
do.7/11/2005
21
What Are the Principal Parts of a Neuron?

• A typical neuron consists of a soma or cell body
  where the nucleus is located, an axon which
  carries an impulse
• (action potential) away from the soma, and
  dendrites which carry information to the soma.
• Neurons interconnect by synapses (spaces over
  which neurotransmitters relay a message from one
  neuron to another).

• Source http//psych.hanover.edu/Krantz/n
  eurotut.html

22
How an Action Potential Moves over the Neural
Membrane

• As the previously polarized nerve cell membrane
  becomes depolarized, the action potential coming
  from the dendrites to the cell body moves toward
  the synaptic junction.

Source http//www.miracosta.cc.ca.us/home/sfoster
/neurons/action.htm
23
How Do Neurons Communicate?

• Neurons do not physically touch each other.
• Neurons communicate with one another through
  various neurotransmitters released from synaptic
  vesicles at the synaptic cleft
• The synaptic cleft separates one neuron from
  another.

• Sourcehttp//www.miracosta.cc.ca.us
  /home/sfoster/neurons/animation.gif.

24
Perception of Pain

• Perception of pain by nociceptors
• Two types of nerve fibers involved
• A fibers (rapidly activated)
• C fibers (activated more slowly)

Source www.acay.com.au/mkause/fear20helplessnes
s/JPG
25
Good and Bad Pain

• A Fibers
• Signal good pain
• Serve as injury warning
• Release glutamate
• C Fibers
• Signal more diffuse, chronic pain
• Pain sources include tissue damage and cancer
• Release substance P

Source http//office.microsoft.com/clipart
26
A Computer-Brain Analogy

• Remember when the older computers didnt have
  enough memory (RAM) to support more complex
  programs?
• Continual bombardment of the brain by stress
  signals results in the inability to process and
  respond adequately to such signals.

Source http//office.microsoft.com/clipart
27
What Is Cybernetics?

• Cybernetics sounds like either robot or computer
  jargon but actually refers to the study of
  communications and control systems in biological,
  mechanical and electronic systems.
• Here, of course, we are only concerned with its
  biological applications (primarily in the nervous
  and endocrine systems).

28
Homeostasis

• State of internal constancy or equilibrium
  necessary to maintain physiological health
• Disrupted by stress

Source http//spwb.com/articles/anti-aging/stre
ss.gif
29
Disturbance of Homeostasis

• Our bodies react to environmental changes
  (stressful or otherwise) by producing hormones
  and neurotransmitters.
• These chemical substances are the messengers and
  mediators of the nervous system and endocrine
  system.
• Stressful events cause the release of adrenalin
  and hormones (e.g., cortisol) from the adrenal
  medulla and cortex, respectively.

30
Then What Are Allostasis and Allostatic Load?

• Since environmental conditions constantly
  fluctuate, allostasis refers to maintaining
  homeostasis despite these changes.
• Likewise, allostatic load refers to Selyes
  notion of wear and tear that results from the
  inefficiency of those messenger and mediator
  processes over time.

31
Allostasis and Allostatic Load

• Brain integrates and coordinates bodily responses
• Physiological and behavioral stress responses
  result in allostatic adaptation
• Over time allostatic load accumulates and can
  cause disease, even death

Source www.sciencebob.com/lab/bodyzone/brain/html
32
Physiological Feedback Loops

• Essential components of a feedback loop
• A sensory receptor sensitive to a disruptive
  stimulus
• An afferent transmission pathway
• A control center (i.e. the brain) serving and
  integrative input/output function
• An efferent (motor) pathway
• An effector to respond to the stimulus

33
Function of Feedback Loops

• Negative feedback loops tend to maintain
  homeostasis (allostasis) by negating the effects
  of the disruptive stimulus.
• Positive feedback loops enhance the disruptive
  stimulus and (in most instances) are harmful.
• Unrelenting cycling of a POSITIVE feedback loop
  will result in death.

34
Psychological Preoccupation Becomes Physiological
in Anorexia

• In a 1977 study published in the New England
  Journal of Medicine, researchers showed
  diminished degradation of plasma cortisol and low
  plasma triiodothyronine (active hormone
  controlling metabolic rate) in young women
  suffering from anorexia nervosa.

35
Psychological Preoccupation Becomes Physiological
(cont.)

• The researchers concluded that anorexia involves
  the following cyclical sequence of events
• A psychological event resulting in preoccupation
  with weight
• Food avoidance leading to an adaptive starvation
  reaction with elevated cortisol levels
  mobilizing stored liver glycogen to increase
  blood glucose

36
Psychological Preoccupation Becomes Physiological
(cont.)

• Elevated blood glucose level leading to further
  loss of appetite
• Diminished levels of triiodothyronine levels from
  the thyroid gland inducing a protective or
  adaptive hypometabolic state (in response to the
  self-imposed starvation conditions) and
• Resulting positive feedback loops (in the absence
  of timely medical intervention) promote adverse
  effects, even death.

37
Some Cautionary Tales from Animal
Studies

• In ancient Etruscan and Roman civilizations a
  kind of fortune-telling ritual called haruspicy
  was practiced.
• As a part of this ritual, the entrails
  (especially the liver) of animals were examined
  by the haruspex in order to predict the future.
• Ironically, examination of the liver and other
  internal organs can enable todays pathologists
  to see not the future but the past.
• Two stress-related animal studies illustrate this
  point.

38
Population Crowding Causes Stress in
Deer

• In the early 1920s, a pair of deer was placed on
  a 150-acre island in Chesapeake Bay.
• The deer population grew until the density
  reached about one deer per acre.
• Then the deer began to die off (in the absence of
  known predators) despite the presence of adequate
  food and water.

Source www.whiskersinn.com/sale/images/320deer.j
pg
39
The Post-mortem Findings

• On autopsy the dead deer were found to have areas
  of atrophy in the liver tissue, marked decrease
  in liver glycogen, and hypoglycemia.
• There was evidence of small (petechial) brain
  hemorrhages and both congestion and hemorrhage of
  the adrenal glands and kidneys.
• These findings suggested what later was
  identified as adrenal stress syndrome.

40
Stress in Minnesota Jack Rabbits

• In a 1939 study also reported in The Bulletin of
  the Atomic Scientists, Minnesota Jack Rabbits
  demonstrated rise and fall in population
  densities but when death rates and densities were
  high, they frequently entered into convulsive
  seizures or comatose states.
• Liver and adrenal pathology, as
• well as hypertension and
• hypoglycemia associated with
• adrenal stress syndrome,
• were observed.

Source http//homestudy.ibea.com/wildlifeID/043ja
ckrabbit.htm
41
Population Density and Behavior (Norway Rats)

• In 1962, John Calhoun (of the National Institutes
  of Health) observed high mortality rates in
  confined wild Norway rats when population
  densities were high as a result of stress-induced
  behavioral changes.

Source http//www.ratbehavior.org/Aggression.htm
42
Population Density and Behavior (Norway Rats)

• Calhoun conducted several experiments involving
  both a quarter-acre enclosure and 6 x 6
  interconnecting pens.
• Calhoun made the following observations

Source http//office.microsoft.com/clipart
43
Behavior changes in females

• Pregnancies were often aborted through
  miscarriage.
• Considerable disruption of normal pre- and
  postpartum maternal behavior (i.e., failure to
  build proper nests, nurse offspring and transport
  litters) occurred.
• Up to 25 of estrus females were so vigorously
  pursued by males that they did not survive.

44
Behavior changes in males

• Some animals became hyperactive, constantly
  fighting.
• These animals also became hypersexual and lost
  the ability to discriminate among estrus and
  non-estrus females, juveniles, and other males.
• Some became cannibalistic.
• Some became withdrawn, demonstrating no interest
  in social interaction.

45
Human Population Density

• The following slide depicts human population
  growth in Europe from an estimated number of 20
  million people in 400 BC to 728 million in 2000
  AD.
• Note that in the last three centuries or so, the
  growth curve becomes progressively exponential or
  logarithmic.

46
Source http//wps.prenhall.com
47
Population Density and Stress in Humans

• Very few studies directly correlate stress of
  crowding with changes in the human brain.
• Compelling evidence now available to link
  neurological changes in human brains to prolonged
  exposure to general stress.

Source www.spokane7.com//archive/asp?monJan2004
48
Population Density and Stress in Humans
(cont.)

• These neurological changes may very well be
  connected with behavioral changes as well.
• For example, crime (which represents a form of
  social pathology) occurs at higher rates in urban
  than suburban areas, but the studies show mixed,
  non-linear correlations above certain density
  levels.
• This may be due to self-treatment by some
  individuals who feel crowding stress when
  moving to less densely populated areas (Regoeczi,
  2002).

49
Population Density andStress in Humans (cont.)

• However, the cages of Calhoun more closely
  resemble the stressful environments of crowded
  prisons and concentration camps.
• Yet even under these conditions, there does not
  seem to be direct linear correlation between
  levels of crowding and levels of violence
  (Brooks, 2004).
• Human physiological changes seem to be much more
  closely linked to animal models than behavioral
  ones, although some degree of extrapolation seems
  reasonable.

50
Stress, Hormones, and the Brain

• Once perceived, stress activates the hypothalamus
  of the brain, triggering a cascade of hormones
  through the hypothalamic-pituitary-adrenal (HPA)
  axis.
• Trigger of the HPA axis results in the release of
  glucocorticoids (e.g., cortisol) from the adrenal
  gland.

51
Stress, Hormones and Brain The
Hypothalamic-Pituitary-Adrenal Axis

• Some neurons in the hypothalamus produce
  corticotropin-releasing factor (CRF).
• The synapses of these cells make contact with
  blood vessels, sending CRF to the adenohypophysis
  (anterior pituitary)
• The pituitary then secretes adrenocorticotrophic
  hormone
• (ACTH) causing glucocorticoid release by the
  adrenal cortex.
• At the same time the adrenal medulla produces
  adrenalin.

• Sourcewww.aafp.org/afp/20000901/1119_f2.gif.
• (The American Academy of Family Physicians)

52
What do glucocorticoids (such as cortisol)
do?

• Glucocorticoids increase blood glucose for the
  fight or flight reaction and thus have
  short-term benefits.
• Over time, frequent release of these
  glucocorticoids adversely affects the hippocampus
  of the brain (the center of numerous
  glucocorticoid receptors).
• Normal levels of these steroids maintain normal
  neuronal function in the hippocampus,
• High levels of these steroids, however, adversely
  affect synaptic transmission and actually
  interfere with glucose uptake by neurons.
• Resultant reduction of neural connections may
  responsively induce memory loss (Seckl, 2005).

53
Daily changes in cortisol in depressed
patients
Source Neuroscience Presentation by Paul
Arfydio, Harvard University. July 14, 2005
54
Jonathan Seckls Conclusions

• Both animals and humans may gradually develop a
  stress-related syndrome involving
• Excess levels of glucocorticoids
• Pathological changes in the structure and
  function of hippocampal cells
• Neuronal death (sometimes)
• Increased numbers of hippocampal glucocorticoid
  receptors, making the brain more sensitive to
  negative feedback control.
• This may be one mechanism of action for certain
  antidepressant drugs.

55
Laboratory Activity Identifying the Brains
Basic Machinery

• Perform a dissection of the sheep (Ovis) brain
  according to the excellent guide presented in the
  following link to the University of Scranton
  Neuroscience Program Dissection Guide
• Sheep Brain Dissection Guide

56
Learning and Conditioning in Planaria (Dugesia
sp.)

• The planarian worm (Dugesia) is a small,
  free-living (i.e. non-parasitic) flatworm
  belonging to the phylum Platyhelminthes.
• The planarian worm is acoelmate (without a body
  cavity enclosing the gut).
• The planarian worm has a nervous system with 2
  light-sensitive eyespots, cephalic ganglia
  (brain), and 2 parallel longitudinal, ventral
  nerve cords.

Source www.anselm.edu//genbios/surveybi04.html
57
Learning and Conditioning in Dugesia
(cont.)

• Materials
• Culture of live Dugesia
• Plastic training maze
• 6V lantern battery and bell wire
• Camels hair artists brush

58
Learning and Conditioning in Dugesia
(cont.)

• Protocol
• Separate the Dugesia into two groups control and
  experimental.
• Place the control animals at the beginning of the
  T-maze and allow them to move through it
  randomly. This will leave a layer of mucus on the
  maze and facilitate movement by others.
• Note the numbers which move left, straight
  ahead, or right when they reach the maze
  intersection.
• If they are reluctant to move at all, then gentle
  prodding with a soft brush may be helpful.

59
Learning and Conditioning in Dugesia
(cont.)

• Now repeat the process with the experimental
  group
• This time apply an electric shock to the water,
  surrounding any worm which moves either straight
  ahead or to the right.
• Repeat the experiment over a weeks time in order
  to observe and record the success of the learning
  process.

60
Learning and Conditioning in Dugesia
(cont.)

• One variant of this experiment involves . . .
• Keeping the animals in the dark and then exposing
  them to a bright light as an electrical shock is
  administered to the water
• Then determining the number of trials required
  for the worms to recoil as though they were
  receiving an electrical shock when exposed only
  to the light source.

61
Observing the Effects of Stress on Learning in
Dugesia

• Worms conditioned to light exposure experiment
  (and presumably stressed after repeated trials)
• Comparatively tested against previously trained
  T-maze worms to determine possible relationship
  between stress of prior conditioning and
  performance in new trials

62
References

• Boyer, R.M.,et al. Cortisol secretion and
  metabolism in anorexia nervosa.NEJM, 294
  (4),1977.
• Brooks, Crystal. Overcrowding and violence in
  federal correctional institutionsAn empirical
  analysis. Retrieved from http//dspace.library.dre
  xel.edu.
• Bresler, Jack B., ed. Human Ecology. Reading,MA.
  Addison-Wesley.1966.
• Calhoun, John. Population density and social
  pathology. Scientific American. Feb.,1962.

63
References (continued)

• Cox, Thomas. Black Hills State University.
  Learning and Conditioning Laboratory. PSYC305L.
  Fall, 2004. Retrieved from http//www.bhsu.edu.
• Duane, Mary, et al. Inquiry in science using an
  animal behavior model. Retrieved from
  http//www.woodrowwilson.org/teachers/bi/1998/plan
  aria/index.htm.
• Hoagland, Hudson. Cybernetics of population
  control. Bulletin of the Atomic Scientists.
  Feb.,1964.
• Marieb, Elaine N. Essentials of Human Anatomy and
  Physiology. San Francisco. Addison-Wesley-Longman.
  2000.

64
References (continued)

• Massachusetts Department of Education.
  Massachusetts Curriculum Frameworks. Retrieved
  from http//www.doe.mass.edu/frameworks.
• Mayer, Emeran A. The neurobiology of stress and
  emotions. Participate/Digestive Health
  Matters.Winter, 2001.
• McEwen, Bruce and Teresa Seeman. Allostatic load
  and allostasis. Retrieved from
• http//www.macses.uscf.edu/Research/allostatic/no
  tebook/allostatic.
• August, 1999.
• National Institute of Child Health and Human
  Development. NIH Backgrounder. http//www.nichd.ni
  h.gov. Sept. 9, 2002.

65
References (continued)

• National Research Council and National Academy of
  Sciences. National Sciences Education Standards.
  Retrieved from http//www.nap.edu/readingroom/book
  s/nses/html/index.html.
• Regoeczi, Wendy C. The impact of density The
  importance on nonlinearity and selection on
  flight and fight response. Social Forces. 81,
  2002. Retrieved from
• http//www.ncsociology.org/sociationtoday/v22/cro
  wding.htm.
• Seckl, Jonathan R. Glucocorticoids, aging, and
  nerve cell damage. Retrieved from
  http//neuroendo.org.uk/index/php/content/view/18/
  11. June, 2005.
• Society for Neuroscience. Brain Facts, a Primer
  on the Brain and Nervous System. Washington.
  Society for Neuroscience.

66
References (continued)

• Spedding, M. and P. Lestage. Synaptic plasticity
  and neuropathology New approaches in drug
  discovery. MedSci (Paris). 211. Jan., 2005.
• United States Dept. of Agriculture. Agricultural
  Research Service. Detecting stress in animals.
  Agricultural Research. Jan.,2002.
• University of Scranton Neuroscience program.
  Welcome to the Sheep brain Dissection Guide.
  Retrieved from http//www.humboldt.edu.

67
Module Assessment Questions

• 1. Describe how the general adaptation syndrome
  (GAS) may have evolved as an adaptation for
  survival.
• 2. What kinds of environmental changes induce
  stress in animals? In people?
• 3. What are the main parts of a neuron, and how
  do neurons work?
• 4. What are synapses, and how do they operate?
  How would neurons be different if they were
  directly connected (like soldered electrical
  wires)?

68
Module Assessment Questions
(II)

• How is pain perceived, and what makes it a
  stressor? Distinguish between the perception of
  good and bad pain.
• What evidence exists to show that high population
  density can induce stress?
• What changes are induced in the brain and
  hormonal system as a result of stress?
• What are the components of a feedback loop?
  Distinguish between the effects of negative and
  positive feedback loops.

69
Module Assessment Questions
(III)

• Distinguish between allostasis and allostatic
  load.
• What similarities and differences exist between
  humans and animals in how they respond to stress?
  How would you account for both the similarities
  and differences?
• What is the hypothalamic-pituitary-adrenal (HPA)
  axis, and how does it operate?
• What kinds of chemical substances are involved in
  the perception of stress and stress responses?
  How do they work?