The Cybernetics of The Cybernetics of Stress:Stress:

Causes, Chemicals, Causes, Chemicals, ConsequencesConsequences

Richard W. Fardy, M.Ed.Richard W. Fardy, M.Ed.

Wilmington High SchoolWilmington High School

Wilmington, MAWilmington, MA

Relevant National Relevant National StandardsStandardsContent Standard CContent Standard C: :

As a result of their activities in grades 9-12, As a result of their activities in grades 9-12, allall

students should develop an understanding students should develop an understanding of:of:

1.1. The cellThe cell

2.2. Biological evolutionBiological evolution

3.3. Matter, energy, and organization of living Matter, energy, and organization of living systemssystems

4.4. Behavior of organismsBehavior of organisms

Relevant Standards from the Massachusetts Curriculum Frameworks (Health)

Standard 5Standard 5: :

““Students will acquire knowledge Students will acquire knowledge about emotions and physical about emotions and physical health,…and will learn skills to health,…and will learn skills to promote self-acceptance, make promote self-acceptance, make decisions and cope with stress.”decisions and cope with stress.”

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

Structure and Function of CellsStructure and Function of Cells:: 2.12.1: Relate cell parts/organelles to their : Relate cell parts/organelles to their

functions.functions.

Human Anatomy and PhysiologyHuman Anatomy and Physiology:: 4.2: Describe how the functions of individual 4.2: Describe how the functions of individual

systems within humans are integrated to systems within humans are integrated to maintain a homeostatic balance….maintain a homeostatic balance….

Evolution and BiodiversityEvolution and Biodiversity:: 5.1: Explain how comparative anatomy…5.1: Explain how comparative anatomy…

and other evidence support the theory of and other evidence support the theory of evolution.evolution.

Juggling and Authentic Juggling and Authentic LearningLearning A juggler must A juggler must

simultaneously simultaneously integrate integrate sensory and sensory and muscular muscular circuitry to circuitry to keep all the keep all the objects in the objects in the air.air. Source: Source: http://office.microsoft.com/cliparthttp://office.microsoft.com/clipart

Juggling and Authentic Juggling and Authentic Learning (cont.)Learning (cont.)

In order for learning to be truly In order for learning to be truly authentic, learning experiences authentic, learning experiences need to show connections to real need to show connections to real life.life.

Events do not always occur in a Events do not always occur in a series of compartmentalized and series of compartmentalized and disconnected boxes but still disconnected boxes but still maintain connections to one maintain connections to one another in some way and manner.another in some way and manner.

Link to LearnLink to Learn

The The raison d’etre raison d’etre for both for both interdisciplinary interdisciplinary instruction and instruction and conceptual linkage conceptual linkage within a particular within a particular subject areasubject area

Source: Source: http://office.microsoft.com/cliparthttp://office.microsoft.com/clipart

Module ObjectivesModule Objectives

To be able to explain what happens in the To be able to explain what happens in the three stages of the three stages of the general adaptation general adaptation syndromesyndrome (GAS). (GAS).

To be able to identify the parts of a neuron To be able to identify the parts of a neuron and explain how neurons transmit and explain how neurons transmit messages.messages.

To be able to define To be able to define cyberneticscybernetics and its and its connection to the nervous and endocrine connection to the nervous and endocrine systems.systems.

To be able to define To be able to define homeostasishomeostasis, , allostasisallostasis,and ,and allostatic loadallostatic load, and explain the , and explain the effects of stress on homeostatic equilibrium.effects of stress on homeostatic equilibrium.

Module Objectives Module Objectives (continued)(continued) To be able to describe the essential To be able to describe the essential

components of a components of a biological feedback biological feedback looploop and to explain the differences in the and to explain the differences in the effects of negative and positive loops.effects of negative and positive loops.

To describe the psychological, To describe the psychological, neurological, and endocrine events that neurological, and endocrine events that occur when anorexia nervosa results occur when anorexia nervosa results from stress.from stress.

To be able to describe how population To be able to describe how population density induces stress in animals and density induces stress in animals and the possible implications for humans.the possible implications for humans.

Module Objectives Module Objectives (continued)(continued) To be able to explain the integration To be able to explain the integration

of the nervous and endocrine of the nervous and endocrine systems in the stress response.systems in the stress response.

To describe the general anatomy of To describe the general anatomy of the brain based on a sheep brain the brain based on a sheep brain dissection.dissection.

To be able to explain how To be able to explain how conditioning and learning may be conditioning and learning may be accomplished in planaria and how accomplished in planaria and how stress may affect this process.stress may affect this process.

Ancient ProverbAncient Proverb

I hear and I forget.I hear and I forget. I see and I remember.I see and I remember. I do and I I do and I

understand.understand.

Confucius

Source: Source: www.ironordeal.com/clipart/persons/Confucius.htm.

Hans Selye (1907-1982)Hans Selye (1907-1982)

Proposed general adaptation syndrome (GAS)

GAS theory first published in Nature in 1936

Described as body’s adaptive response to stress

Just What Exactly Is Just What Exactly Is Stress?Stress?

Initially Initially identified by identified by Selye as Selye as “noxious “noxious agents.”agents.”

Became known Became known as as stress stress syndromesyndrome..

Source: Source: www.alnoorhospital.com/uploadedfiles/common/stress/jpgwww.alnoorhospital.com/uploadedfiles/common/stress/jpg

Selye’s Three Stages of Selye’s Three Stages of StressStress Stage 1Stage 1: The : The alarm reactionalarm reaction in which the in which the

body prepares itself for “fight or flight.”body prepares itself for “fight or flight.” Stage 2Stage 2: Since the first stage cannot : Since the first stage cannot

long be sustained, there is a general long be sustained, there is a general resistance to the stress which is resistance to the stress which is established.established.

Stage 3Stage 3: If the stress is continued for a : If the stress is continued for a long period of time, then eventual long period of time, then eventual exhaustion results (the body’s response exhaustion results (the body’s response to prolonged “wear and tear”).to prolonged “wear and tear”).

Selye’s Final AnalysisSelye’s Final Analysis

Stress includes both internal and external factors.

Factors involve the “nonspecific response of the body to any demand."

The “Fight or Flight” The “Fight or Flight” ResponseResponse

1.1. Perceive extreme Perceive extreme danger or danger or distressdistress

2.2. Neurons (nerve Neurons (nerve cells) in brain cells) in brain send entire body send entire body into “high gear”into “high gear”

3.3. Responsively Responsively prepare for “fight prepare for “fight or flight”or flight”

Source: Source: www.saludparati.com/entres.htmwww.saludparati.com/entres.htm

Selye’s Third StageSelye’s Third Stage

Challenged by Challenged by physiological, physiological, psychological, and psychological, and environmental environmental changes changes (stressors)(stressors)

Failure to Failure to accommodate to accommodate to changes can lead changes can lead to to exhaustionexhaustion Source: Source: www.bet.com/Health/Archiveswww.bet.com/Health/Archives

What Are Neurons?What Are Neurons?

Neurons are the specialized cells of which Neurons are the specialized cells of which nerve tissue is composed.nerve tissue is composed.

Neurons have the ability to send Neurons have the ability to send “messages” to each other through the “messages” to each other through the release of chemical substances called release of chemical substances called neurotransmitters.neurotransmitters.

Neurons are also electrical in nature, Neurons are also electrical in nature, maintaining polarity through electrical maintaining polarity through electrical gradients established by ions on the inside gradients established by ions on the inside and outside of their cell membranes.and outside of their cell membranes.

Neurons send electrical signals (Neurons send electrical signals (action action potentialspotentials) by depolarizing.) by depolarizing.

What Do Neurons Look What Do Neurons Look Like?Like?

Nerve smear containing neuron, axon, dendrite, cell body,

nucleus, and nucleolus

Source: Source: http://facstaff.bloomu.edu/jhranitz/teaching/APHNT/Laboratory%20Pictures.htmhttp://facstaff.bloomu.edu/jhranitz/teaching/APHNT/Laboratory%20Pictures.htm

Neurons labeled Neurons labeled withwith fluorescent proteins fluorescent proteins

Source: Joshua Sanes, Harvard University. Lecture:”Neurons: how they look and what they Source: Joshua Sanes, Harvard University. Lecture:”Neurons: how they look and what they do.7/11/2005do.7/11/2005

What Are the Principal What Are the Principal Parts of a Neuron?Parts of a Neuron? A typical neuron consists A typical neuron consists

of a soma or cell body of a soma or cell body where the nucleus is where the nucleus is located, an axon which located, an axon which carries an impulse carries an impulse ((action potentialaction potential) away ) away from the soma, and from the soma, and dendrites which carry dendrites which carry information to the soma. information to the soma.

Neurons interconnect by Neurons interconnect by synapses synapses (spaces over (spaces over which neurotransmitters which neurotransmitters relay a message from relay a message from one neuron to another).one neuron to another).

Source:Source: http://psych.hanover.edu/Krantz/neurotut.html http://psych.hanover.edu/Krantz/neurotut.html

How an Action Potential How an Action Potential Moves over the Neural Moves over the Neural MembraneMembrane As the previously As the previously

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

Source: Source: http://www.miracosta.cc.ca.us/home/sfoster/neurons/action.hthttp://www.miracosta.cc.ca.us/home/sfoster/neurons/action.htmm

How Do Neurons How Do Neurons Communicate?Communicate? Neurons do not Neurons do not

physically touch physically touch each other.each other.

Neurons Neurons communicate with communicate with one another through one another through various various neurotransmitters neurotransmitters released from released from synaptic vesicles at synaptic vesicles at the the synaptic cleftsynaptic cleft

The synaptic cleft The synaptic cleft separates one separates one neuron from neuron from another.another.

Source:http://www.miracosta.cc.ca.us/home/sfoster/neurSource:http://www.miracosta.cc.ca.us/home/sfoster/neurons/animation.gif.ons/animation.gif.

Perception of PainPerception of Pain

Perception of pain Perception of pain by by nociceptorsnociceptors

TwoTwo types of nerve types of nerve fibers involved:fibers involved:

1.1. ““A” fibers (rapidly A” fibers (rapidly activated)activated)

2.2. ““C” fibers C” fibers (activated more (activated more slowly)slowly)Source: Source: www.acay.com.au/~mkause/fearwww.acay.com.au/~mkause/fear

%20helplessness/JPG%20helplessness/JPG

““Good” and “Bad” Good” and “Bad” PainPain

“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: Source: http://office.microsoft.com/cliparthttp://office.microsoft.com/clipart

A Computer-Brain A Computer-Brain AnalogyAnalogy

Remember when the older computers didn’t 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: Source: http://office.microsoft.com/cliparthttp://office.microsoft.com/clipart

What Is Cybernetics?What Is Cybernetics?

CyberneticsCybernetics sounds like either robot sounds like either robot or computer jargon but actually refers or computer jargon but actually refers to the to the study of communications and study of communications and control systems in biological, control systems in biological, mechanical and electronic systemsmechanical and electronic systems..

Here, of course, we are only Here, of course, we are only concerned with its biological concerned with its biological applications (primarily in the nervous applications (primarily in the nervous and endocrine systems).and endocrine systems).

HomeostasisHomeostasis

State of State of internal internal constancy or constancy or equilibrium equilibrium necessary to necessary to maintain maintain physiological physiological healthhealth

Disrupted by Disrupted by

stressstress Source: Source: http://spwb.com/articles/anti-aging/stress.gifhttp://spwb.com/articles/anti-aging/stress.gif

Disturbance of Disturbance of HomeostasisHomeostasis

Our bodies react to environmental Our bodies react to environmental changes (stressful or otherwise) by changes (stressful or otherwise) by producing hormones and producing hormones and neurotransmitters. neurotransmitters.

These chemical substances are the These chemical substances are the messengers and mediators of the messengers and mediators of the nervous system and endocrine system.nervous system and endocrine system.

Stressful events cause the release of Stressful events cause the release of adrenalin and hormones (e.g., cortisol) adrenalin and hormones (e.g., cortisol) from the adrenal medulla and cortex, from the adrenal medulla and cortex, respectively.respectively.

Then What Are Then What Are Allostasis and Allostasis and Allostatic Load?Allostatic Load? Since environmental conditions Since environmental conditions

constantly fluctuate, constantly fluctuate, allostasisallostasis refers refers to maintaining homeostasis to maintaining homeostasis despitedespite these changes.these changes.

Likewise, Likewise, allostatic loadallostatic load refers to refers to Selye’s notion of “wear and tear” that Selye’s notion of “wear and tear” that results from the inefficiency of those results from the inefficiency of those messenger and mediator processes messenger and mediator processes over time.over time.

Allostasis and Allostatic Allostasis and Allostatic LoadLoad

Brain integrates Brain integrates and coordinates and coordinates bodily responsesbodily responses

Physiological and Physiological and behavioral stress behavioral stress responses result in responses result in allostatic allostatic adaptationadaptation

Over time allostatic Over time allostatic load accumulates load accumulates and can cause and can cause disease, even deathdisease, even deathSource: Source: www.sciencebob.com/lab/bodyzone/brain/htmlwww.sciencebob.com/lab/bodyzone/brain/html

Physiological Feedback Physiological Feedback LoopsLoopsEssential components of a feedback loop:Essential components of a feedback loop: A sensory receptorA sensory receptor sensitive to a sensitive to a

disruptive stimulusdisruptive stimulus An afferent transmission pathway An afferent transmission pathway A control center A control center (i.e. the brain) serving (i.e. the brain) serving

and integrative input/output functionand integrative input/output function An efferent (motor) pathway An efferent (motor) pathway An effector An effector to respond to the stimulusto respond to the stimulus

Function of Feedback Function of Feedback LoopsLoops Negative feedback loops tend to Negative feedback loops tend to

maintain homeostasis (maintain homeostasis (allostasisallostasis) ) by negating the effects of the by negating the effects of the disruptive stimulus.disruptive stimulus.

Positive feedback loops enhance Positive feedback loops enhance the disruptive stimulus and (in the disruptive stimulus and (in most instances) are harmful.most instances) are harmful.

Unrelenting cycling of a POSITIVE Unrelenting cycling of a POSITIVE feedback loop will result in feedback loop will result in deathdeath..

Psychological Preoccupation Psychological Preoccupation Becomes Physiological in Becomes Physiological in AnorexiaAnorexia In a 1977 study published in theIn a 1977 study published in the

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

Psychological Psychological Preoccupation Becomes Preoccupation Becomes Physiological (cont.)Physiological (cont.) The researchers concluded that The researchers concluded that

anorexia involves the following anorexia involves the following cyclical sequence of events:cyclical sequence of events:

1.1. A psychological event resulting in A psychological event resulting in preoccupation with weight;preoccupation with weight;

2.2. Food avoidance leading to an Food avoidance leading to an adaptive “starvation reaction” with adaptive “starvation reaction” with elevated cortisol levels mobilizing elevated cortisol levels mobilizing stored liver glycogen to increase stored liver glycogen to increase blood glucose;blood glucose;

Psychological Psychological Preoccupation Becomes Preoccupation Becomes Physiological (cont.)Physiological (cont.)3.3. Elevated blood glucose level leading to Elevated blood glucose level leading to

further loss of appetite;further loss of appetite;4.4. Diminished levels of triiodothyronine Diminished levels of triiodothyronine

levels from the thyroid gland inducing a levels from the thyroid gland inducing a protective or adaptive hypometabolic protective or adaptive hypometabolic state (in response to the self-imposed state (in response to the self-imposed starvation conditions); andstarvation conditions); and

5.5. Resulting positive feedback loops (in Resulting positive feedback loops (in the absence of timely medical the absence of timely medical intervention) promote adverse effects, intervention) promote adverse effects, even death.even death.

Some Cautionary Tales Some Cautionary Tales fromfrom Animal Studies Animal Studies In ancient Etruscan and Roman civilizations a In ancient Etruscan and Roman civilizations a

kind of fortune-telling ritual called kind of fortune-telling ritual called haruspicy haruspicy was practiced.was practiced.

As a part of this ritual, the entrails As a part of this ritual, the entrails (especially the liver) of animals were (especially the liver) of animals were examined by the examined by the haruspexharuspex in order to in order to predict the future.predict the future.

Ironically, examination of the liver and other Ironically, examination of the liver and other internal organs can enable today’s internal organs can enable today’s pathologists to see not the future but the pathologists to see not the future but the past.past.

Two stress-related animal studies illustrate Two stress-related animal studies illustrate this point.this point.

Population Crowding Population Crowding CausesCauses Stress in Deer Stress in Deer In the early 1920’s, a In the early 1920’s, a

pair of deer was pair of deer was placed on a 150-acre placed on a 150-acre island in Chesapeake island in Chesapeake Bay.Bay.

The deer population The deer population grew until the density grew until the density reached about one reached about one deer per acre.deer per acre.

Then the deer began Then the deer began to die off (in the to die off (in the absence of known absence of known predators) despite the predators) despite the presence of adequate presence of adequate food and water.food and water.

Source: Source: www.whiskersinn.com/sale/images/3%20deer.jpwww.whiskersinn.com/sale/images/3%20deer.jpgg

The Post-mortem The Post-mortem FindingsFindings On autopsy the dead deer were found On autopsy the dead deer were found

to have areas of atrophy in the liver to have areas of atrophy in the liver tissue, marked decrease in liver tissue, marked decrease in liver glycogen, and hypoglycemia.glycogen, and hypoglycemia.

There was evidence of small There was evidence of small (petechial) brain hemorrhages and (petechial) brain hemorrhages and both congestion and hemorrhage of both congestion and hemorrhage of the adrenal glands and kidneys.the adrenal glands and kidneys.

These findings suggested what later These findings suggested what later was identified as was identified as adrenal stress adrenal stress syndromesyndrome..

Stress in Minnesota Jack Stress in Minnesota Jack RabbitsRabbits

In a 1939 study also reported In a 1939 study also reported in in The Bulletin of the Atomic The Bulletin of the Atomic Scientists, Scientists, Minnesota Jack Minnesota Jack Rabbits demonstrated rise Rabbits demonstrated rise and fall in population and fall in population densities but when death densities but when death rates and densities were high, rates and densities were high, they frequently entered into they frequently entered into convulsive seizures or convulsive seizures or comatose states.comatose states.

Liver and adrenal pathology, Liver and adrenal pathology, as as well as hypertension andwell as hypertension andhypoglycemia associated with hypoglycemia associated with adrenal stress syndromeadrenal stress syndrome, , were observed.were observed.

Source: Source: http://homestudy.ibea.com/wildlifeID/043jackrabbit.hthttp://homestudy.ibea.com/wildlifeID/043jackrabbit.htmm

Population Density Population Density andand Behavior (Norway Behavior (Norway Rats)Rats) In 1962, John In 1962, John

Calhoun (of the Calhoun (of the National Institutes of National Institutes of Health) observed Health) observed high mortality rates high mortality rates in confined wild in confined wild Norway rats when Norway rats when population densities population densities were high as a result were high as a result of stress-induced of stress-induced behavioral changes.behavioral changes. Source: http://www.ratbehavior.org/Aggression.htmSource: http://www.ratbehavior.org/Aggression.htm

Population Density andPopulation Density and Behavior (Norway Rats) Behavior (Norway Rats)

Calhoun conducted Calhoun conducted several experiments several experiments involving both a involving both a quarter-acre quarter-acre enclosure and 6’ x enclosure and 6’ x 6’ interconnecting 6’ interconnecting pens.pens.

Calhoun made the Calhoun made the following following observations:observations:

Source: Source: http://office.microsoft.com/cliparthttp://office.microsoft.com/clipart

Behavior changes in Behavior changes in femalesfemales

1.1. Pregnancies were often aborted Pregnancies were often aborted through miscarriage.through miscarriage.

2.2. Considerable disruption of normal Considerable disruption of normal pre- and postpartum maternal pre- and postpartum maternal behavior (i.e., failure to build behavior (i.e., failure to build proper nests, nurse offspring and proper nests, nurse offspring and transport litters) occurred.transport litters) occurred.

3.3. Up to 25% of estrus females were Up to 25% of estrus females were so vigorously pursued by males so vigorously pursued by males that they did not survivethat they did not survive..

Behavior changes in Behavior changes in malesmales

1.1. Some animals became hyperactive, Some animals became hyperactive, constantly fighting.constantly fighting.

2.2. These animals also became These animals also became hypersexual and lost the ability to hypersexual and lost the ability to discriminate among estrus and non-discriminate among estrus and non-estrus females, juveniles, and other estrus females, juveniles, and other males.males.

3.3. Some became cannibalistic.Some became cannibalistic.4.4. Some became withdrawn, Some became withdrawn,

demonstrating no interest in social demonstrating no interest in social interaction.interaction.

Human Population Human Population DensityDensity The following slide depicts human The following slide depicts human

population growth in Europe from population growth in Europe from an estimated number of 20 million an estimated number of 20 million people in 400 BC to 728 million in people in 400 BC to 728 million in 2000 AD.2000 AD.

Note that in the last three Note that in the last three centuries or so, the growth curve centuries or so, the growth curve becomes progressively becomes progressively exponential or logarithmic.exponential or logarithmic.

Source: Source: http://wps.prenhall.comhttp://wps.prenhall.com

Population Density and Population Density and Stress in HumansStress in Humans

Very few studies Very few studies directly correlate directly correlate stress of crowding stress of crowding with changes in the with changes in the human brain.human brain.

Compelling evidence Compelling evidence now available to link now available to link neurological changes neurological changes in human brains to in human brains to prolonged exposure prolonged exposure to general stressto general stress..

Source:Source: www.spokane7.com/…/archive/asp? www.spokane7.com/…/archive/asp?mon=Jan2004mon=Jan2004

Population Density Population Density andand Stress in Humans Stress in Humans (cont.)(cont.) These neurological changes may very well be These neurological changes may very well be

connected with behavioral changes as well.connected with behavioral changes as well. For example, crime (which represents a form For example, crime (which represents a form

of social pathology) occurs at higher rates in of social pathology) occurs at higher rates in urban than suburban areas, but the studies urban than suburban areas, but the studies show mixed, non-linear correlations above show mixed, non-linear correlations above certain density levels.certain density levels.

This may be due to “self-treatment” by some This may be due to “self-treatment” by some individuals who feel “crowding stress” when individuals who feel “crowding stress” when moving to less densely populated areas moving to less densely populated areas (Regoeczi, 2002).(Regoeczi, 2002).

Population Density Population Density andandStress in Humans Stress in Humans (cont.)(cont.) However, the cages of Calhoun more closely However, the cages of Calhoun more closely

resemble the stressful environments of resemble the stressful environments of crowded prisons and concentration camps.crowded prisons and concentration camps.

Yet even under these conditions, there does Yet even under these conditions, there does not seem to be direct linear correlation not seem to be direct linear correlation between levels of crowding and levels of between levels of crowding and levels of violence (Brooks, 2004).violence (Brooks, 2004).

Human physiological changes seem to be Human physiological changes seem to be much more closely linked to animal models much more closely linked to animal models than behavioral ones, although some degree than behavioral ones, although some degree of extrapolation seems reasonable.of extrapolation seems reasonable.

Stress, Hormones, and the Stress, Hormones, and the BrainBrain

Once perceived, stress activates Once perceived, stress activates the the hypothalamus hypothalamus of the brain, of the brain, triggering a cascade of hormones triggering a cascade of hormones through the through the hypothalamic-hypothalamic-pituitary-adrenal pituitary-adrenal (HPA)(HPA) axis.axis.

Trigger of the HPA axis results in Trigger of the HPA axis results in the release of glucocorticoids the release of glucocorticoids (e.g., cortisol) from the adrenal (e.g., cortisol) from the adrenal gland.gland.

Stress, Hormones and Brain: Stress, Hormones and Brain: The Hypothalamic-Pituitary-The Hypothalamic-Pituitary-Adrenal AxisAdrenal Axis Some neurons in theSome neurons in the

hypothalamus hypothalamus produce produce corticotropin-releasing corticotropin-releasing factor (CRF).factor (CRF).

The synapses of these The synapses of these cells make contact with cells make contact with blood vessels, sending blood vessels, sending CRF to the CRF to the adenohypophysis adenohypophysis (anterior (anterior pituitary)pituitary)

The pituitary then secretes The pituitary then secretes adrenocorticotrophic adrenocorticotrophic hormone hormone (ACTH) causing (ACTH) causing glucocorticoid release by glucocorticoid release by the adrenal cortex.the adrenal cortex.

At the same time the At the same time the adrenal medulla produces adrenal medulla produces adrenalinadrenalin..

Source:Source:www.aafp.org/afp/20000901/1119_f2.gif.www.aafp.org/afp/20000901/1119_f2.gif. (The American Academy of Family Physicians)(The American Academy of Family Physicians)

What do What do glucocorticoids glucocorticoids (such as cortisol) do? (such as cortisol) do? Glucocorticoids increase blood glucose for the Glucocorticoids increase blood glucose for the

“fight or flight” reaction and thus have short-“fight or flight” reaction and thus have short-term benefits. term benefits.

Over time, frequent release of these Over time, frequent release of these glucocorticoids adversely affects the glucocorticoids adversely affects the hippocampus of the brain (the center of hippocampus of the brain (the center of numerous glucocorticoid receptors). numerous glucocorticoid receptors).

Normal levels of these steroids maintain normal Normal levels of these steroids maintain normal neuronal function in the hippocampus,neuronal function in the hippocampus,

High levels of these steroids, however, High levels of these steroids, however, adversely affect synaptic transmission and adversely affect synaptic transmission and actually interfere with glucose uptake by actually interfere with glucose uptake by neurons. neurons.

Resultant reduction of neural connections may Resultant reduction of neural connections may responsively induce memory loss (Seckl, 2005).responsively induce memory loss (Seckl, 2005).

Daily changes in Daily changes in cortisolcortisol in depressed in depressed patients patients

Source: Neuroscience Presentation by Paul Arfydio, Harvard University. July 14, 2005

Jonathan Seckl’sJonathan Seckl’s Conclusions Conclusions Both animals and humans may gradually Both animals and humans may gradually

develop a stress-related syndrome develop a stress-related syndrome involving:involving:

1.1. Excess levels of glucocorticoidsExcess levels of glucocorticoids2.2. Pathological changes in the structure and Pathological changes in the structure and

function of hippocampal cellsfunction of hippocampal cells3.3. Neuronal death (sometimes)Neuronal death (sometimes)4.4. Increased numbers of hippocampal Increased numbers of hippocampal

glucocorticoid receptors, making the brain glucocorticoid receptors, making the brain more sensitive to negative feedback more sensitive to negative feedback control.control.

This may be one mechanism of action for This may be one mechanism of action for certain antidepressant drugs.certain antidepressant drugs.

Laboratory Activity: Laboratory Activity: IdentifyingIdentifying the Brain’s Basic the Brain’s Basic MachineryMachinery Perform a dissection of the sheep Perform a dissection of the sheep

(Ovis) (Ovis) brain according to the brain according to the excellent guide presented in the excellent guide presented in the following link to the following link to the University of University of Scranton Neuroscience Program Scranton Neuroscience Program Dissection GuideDissection Guide::

Sheep Brain Dissection GuideSheep Brain Dissection Guide

Learning and Learning and ConditioningConditioning in Planaria ( in Planaria (Dugesia Dugesia sp.)sp.) The planarian worm The planarian worm

(Dugesia) (Dugesia) is a small, free-is a small, free-living (i.e. non-parasitic) living (i.e. non-parasitic) flatworm belonging to the flatworm belonging to the phylum Platyhelminthes.phylum Platyhelminthes.

The planarian worm is The planarian worm is acoelmate (without a body acoelmate (without a body cavity enclosing the gut). cavity enclosing the gut).

The planarian worm has a The planarian worm has a nervous system with 2 nervous system with 2 light-sensitive eyespots, light-sensitive eyespots, cephalic ganglia (“brain”), cephalic ganglia (“brain”), and 2 parallel longitudinal, and 2 parallel longitudinal, ventral nerve cords.ventral nerve cords. Source: Source:

www.anselm.edu/…/genbios/surveybi04.htmlwww.anselm.edu/…/genbios/surveybi04.html

Learning and ConditioningLearning and Conditioning in in Dugesia Dugesia (cont.)(cont.)

MaterialsMaterials:: Culture of live Culture of live Dugesia Dugesia Plastic training mazePlastic training maze 6V lantern battery and bell wire6V lantern battery and bell wire Camel’s hair artist’s brushCamel’s hair artist’s brush

Learning and Learning and ConditioningConditioning in in Dugesia Dugesia (cont.)(cont.)ProtocolProtocol:: Separate the Separate the Dugesia Dugesia into two groups: into two groups: control control

and and experimentalexperimental.. Place the control animals at the beginning of Place the control animals at the beginning of

the T-maze and allow them to move through it the T-maze and allow them to move through it randomly. This will leave a layer of mucus on randomly. This will leave a layer of mucus on the maze and facilitate movement by others.the maze and facilitate movement by others.

Note the numbers which move left, straight Note the numbers which move left, straight ahead, or right when they reach the maze ahead, or right when they reach the maze intersection.intersection.

If they are reluctant to move at all, then gentle If they are reluctant to move at all, then gentle prodding with a soft brush may be helpful.prodding with a soft brush may be helpful.

Learning and Learning and ConditioningConditioning in in Dugesia Dugesia (cont.) (cont.) Now repeat the process with the Now repeat the process with the

experimental group:experimental group: This time apply an electric shock to This time apply an electric shock to

the water, surrounding any worm the water, surrounding any worm which moves either straight ahead or which moves either straight ahead or to the right.to the right.

Repeat the experiment over a week’s Repeat the experiment over a week’s time in order to observe and record time in order to observe and record the success of the learning process.the success of the learning process.

Learning and Learning and Conditioning Conditioning in in Dugesia Dugesia (cont.)(cont.)

One variant of this experiment involves . . One variant of this experiment involves . . . .

Keeping the animals in the dark and then Keeping the animals in the dark and then exposing them to a bright light as an exposing them to a bright light as an electrical shock is administered to the electrical shock is administered to the water;water;

Then determining the number of trials Then determining the number of trials required for the worms to recoil as though required for the worms to recoil as though they were receiving an electrical shock they were receiving an electrical shock when exposed only to the light source.when exposed only to the light source.

Observing the Effects of Observing the Effects of Stress on Learning in Stress on Learning in DugesiaDugesia Worms conditioned to light Worms conditioned to light

exposure experiment (and exposure experiment (and presumably stressed after repeated presumably stressed after repeated trials)trials)

Comparatively tested against Comparatively tested against previously trained T-maze worms to previously trained T-maze worms to determine possible relationship determine possible relationship between stress of prior conditioning between stress of prior conditioning and performance in new trialsand performance in new trials

ReferencesReferences

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Module Assessment Module Assessment Questions Questions 1. Describe how the 1. Describe how the general adaptation general adaptation

syndromesyndrome (GAS) may have evolved as an (GAS) may have evolved as an adaptation for survival.adaptation for survival.

2. What kinds of environmental changes 2. What kinds of environmental changes induce stress in animals? In people?induce stress in animals? In people?

3. What are the main parts of a neuron, 3. What are the main parts of a neuron, and how do neurons work?and how do neurons work?

4. What are synapses, and how do they 4. What are synapses, and how do they operate? How would neurons be different operate? How would neurons be different if they were directly connected (like if they were directly connected (like soldered electrical wires)?soldered electrical wires)?

Module Assessment Module Assessment QuestionsQuestions (II) (II)5.5. How is pain perceived, and what makes it How is pain perceived, and what makes it

a stressor? Distinguish between the a stressor? Distinguish between the perception of “good” and “bad” pain.perception of “good” and “bad” pain.

6.6. What evidence exists to show that high What evidence exists to show that high population density can induce stress?population density can induce stress?

7.7. What changes are induced in the brain and What changes are induced in the brain and hormonal system as a result of stress?hormonal system as a result of stress?

8.8. What are the components of a feedback What are the components of a feedback loop? Distinguish between the effects of loop? Distinguish between the effects of negative and positive feedback loops.negative and positive feedback loops.

Module Assessment Module Assessment QuestionsQuestions (III) (III)

9.9. Distinguish between Distinguish between allostasisallostasis and and allostatic loadallostatic load..

10.10. What similarities and differences exist What similarities and differences exist between humans and animals in how they between humans and animals in how they respond to stress? How would you respond to stress? How would you account for both the similarities and account for both the similarities and differences?differences?

11.11. What is the What is the hypothalamic-pituitary-hypothalamic-pituitary-adrenaladrenal (HPA) (HPA) axisaxis, and how does it , and how does it operate?operate?

12.12. What kinds of chemical substances are What kinds of chemical substances are involved in the perception of stress and involved in the perception of stress and stress responses? How do they work?stress responses? How do they work?