Cybernetics of Stress

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8/22/2019 Cybernetics of Stress http://slidepdf.com/reader/full/cybernetics-of-stress 1/69 The Cybernetics of Stress: Causes, Chemicals, Consequences Richard W. Fardy, M.Ed. Wilmington High School Wilmington, MA 

Transcript of Cybernetics of Stress

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The Cybernetics of Stress:

Causes, Chemicals, Consequences

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

Wilmington, MA 

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Relevant National

StandardsContent Standard C:

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

students should develop an understanding of: 

1. The cell

2. Biological evolution

3. Matter, energy, and organization of livingsystems

4. Behavior of organisms

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Relevant Standards from the 

Massachusetts Curriculum

Frameworks (Health) Standard 5:

“Students will acquire knowledgeabout emotions and physicalhealth,…and will learn skills topromote self-acceptance, make

decisions and cope with stress.” 

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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 anatomy…and 

other evidence support the theory of evolution.

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Juggling and Authentic Learning

 A juggler mustsimultaneously

integratesensory andmuscular

circuitry to keepall the objects inthe air.

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

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Juggling and Authentic Learning(cont.)

In order for learning to be trulyauthentic, learning experiences need

to show connections to real life. Events do not always occur in a

series of compartmentalized and

disconnected boxes but still maintainconnections to one another in someway and manner.

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Link to Learn

The raison d’etre for

both interdisciplinaryinstruction andconceptual linkage

within a particularsubject area

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

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Module Objectives

To be able to explain what happens in thethree stages of the general adaptation 

syndrome (GAS). To be able to identify the parts of a neuron

and explain how neurons transmitmessages.

To be able to define cybernetics and itsconnection to the nervous and endocrinesystems.

To be able to define homeostasis ,

allostasis ,and allostatic load , and explain

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Module Objectives

(continued) To be able to describe the essential

components of a biological feedback loop  and to explain the differences in the effectsof negative and positive loops.

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

To be able to describe how populationdensity induces stress in animals and thepossible implications for humans.

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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 braindissection.

To be able to explain how conditioningand learning may be accomplished inplanaria and how stress may affect

this process.

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Hans Selye (1907-1982)

Proposed general adaptationsyndrome (GAS)

GAS theory first published inNature in 1936

Described as body’s adaptiveresponse to stress

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Just What Exactly Is Stress?

Initiallyidentified by

Selye as“noxiousagents.” 

Became knownas stress syndrome .

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

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Selye’s Three Stages of Stress 

Stage 1: The alarm reaction in which thebody prepares itself for “fight or flight.” 

Stage 2: Since the first stage cannot longbe sustained, there is a general resistanceto the stress which is established.

Stage 3: If the stress is continued for a

long period of time, then eventualexhaustion results (the body’s response toprolonged “wear and tear”). 

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Selye’s Final Analysis 

Stress includes both internaland external factors.

Factors involve the “nonspecificresponse of the body to any

demand." 

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  The “Fight or Flight” Response 

1. Perceive extremedanger or distress

2. Neurons (nervecells) in brain sendentire body into“high gear” 

3. Responsivelyprepare for “fightor flight” 

Source: www.saludparati.com/entres.htm

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Selye’s Third Stage 

Challenged byphysiological,

psychological, andenvironmentalchanges (stressors)

Failure to

accommodate tochanges can leadto exhaustion  

Source: www.bet.com/Health/Archives

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What Are Neurons?

Neurons are the specialized cells of whichnerve tissue is composed.

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

Neurons are also electrical in nature,

maintaining polarity through electricalgradients established by ions on the insideand outside of their cell membranes.

Neurons send electrical signals (action 

 potentials ) by depolarizing.

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What Do Neurons Look Like?

Nerve smear containing neuron, axon,

dendrite, cell body, nucleus, and

nucleolus

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

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Neurons labeled with

fluorescent proteins

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

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What Are the Principal Parts

of a Neuron?  A typical neuron consists of 

a soma or cell body wherethe nucleus is located, anaxon which carries an

impulse(action potential ) awayfrom the soma, anddendrites which carryinformation to the soma.

Neurons interconnect bysynapses (spaces overwhich neurotransmittersrelay a message from oneneuron to another).

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

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How an Action PotentialMoves over the Neural

Membrane  As the previously

polarized nerve

cell membranebecomesdepolarized, theaction potential  

coming from thedendrites to thecell body movestoward the

synaptic junction.Source:

http://www.miracosta.cc.ca.us/home/sfoster/neurons/action.htm

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How Do Neurons Communicate?

Neurons do notphysically toucheach other.

Neuronscommunicate withone another throughvariousneurotransmittersreleased fromsynaptic vesicles atthe synaptic cleft  

The synaptic cleftseparates oneneuron from

another.

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

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Perception of Pain

Perception of painby nociceptors 

Two types of nervefibers involved:

1. “A” fibers (rapidlyactivated)

2. “C” fibers (activatedmore slowly)

Source: www.acay.com.au/~mkause/fear%20helplessness/JPG

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“Good” and “Bad” Pain 

“A” Fibers:

Signal “good pain” 

Serve as injury warning Release glutamate

“C” Fibers:

Signal more diffuse, chronicpain

Pain sources include tissue

damage and cancer“ ”

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

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A Computer-Brain Analogy

Remember when the oldercomputers didn’t haveenough memory (RAM) tosupport more complexprograms?

Continual bombardment

of the brain by stresssignals results in theinability to process andrespond adequately tosuch signals.

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

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What Is Cybernetics?

Cybernetics sounds like either robot orcomputer jargon but actually refers to

the study of communications and control systems in biological, mechanical and electronic systems .

Here, of course, we are only concernedwith its biological applications(primarily in the nervous and endocrinesystems).

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Homeostasis

State of internalconstancy orequilibriumnecessary tomaintainphysiological

health

Disrupted bystress

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

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Disturbance of Homeostasis

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

These chemical substances are themessengers and mediators of the nervoussystem and endocrine system.

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

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Then What Are Allostasis

and Allostatic Load? Since environmental conditions constantly

fluctuate, allostasis refers to maintaining

homeostasis despite these changes. Likewise, allos tatic lo ad  refers to Selye’s

notion of “wear and tear” that results fromthe inefficiency of those messenger and

mediator processes over time.

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Allostasis and Allostatic Load

Brain integratesand coordinatesbodily responses

Physiological andbehavioral stressresponses result inallostatic adaptation

Over time allostaticload accumulatesand can causedisease, even deathSource: www.sciencebob.com/lab/bodyzone/brain/html

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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 

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Function of Feedback Loops

Negative feedback loops tend tomaintain homeostasis (allostasis ) by

negating the effects of the disruptivestimulus.

Positive feedback loops enhance the

disruptive stimulus and (in mostinstances) are harmful.

Unrelenting cycling of a POSITIVE

feedback loop will result in death.

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Psychological PreoccupationBecomes Physiological in Anorexia

In a 1977 study published in the New England Journal of Medicine,

researchers showed diminisheddegradation of plasma cortisol and lowplasma triiodothyronine (active

hormone controlling metabolic rate) inyoung women suffering from anorexianervosa.

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Psychological PreoccupationBecomes Physiological (cont.)

The researchers concluded that anorexiainvolves the following cyclical sequence

of events:1.  A psychological event resulting in

preoccupation with weight;

2. Food avoidance leading to an adaptive

“starvation reaction” with elevatedcortisol levels mobilizing stored liverglycogen to increase blood glucose;

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Psychological PreoccupationBecomes Physiological (cont.)

3. Elevated blood glucose level leading tofurther loss of appetite;

4. Diminished levels of triiodothyroninelevels from the thyroid gland inducing aprotective or adaptive hypometabolicstate (in response to the self-imposed

starvation conditions); and5. Resulting positive feedback loops (in the

absence of timely medical intervention)promote adverse effects, even death.

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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 (especiallythe liver) of animals were examined by theharuspex  in order to predict the future.

Ironically, examination of the liver and other

internal organs can enable today’s pathologiststo see not the future but the past.

Two stress-related animal studies illustrate thispoint.

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The Post-mortem Findings

On autopsy the dead deer were found tohave areas of atrophy in the liver tissue,

marked decrease in liver glycogen, andhypoglycemia.

There was evidence of small (petechial)brain hemorrhages and both congestion

and hemorrhage of the adrenal glands andkidneys.

These findings suggested what later wasidentified as adrenal stress syndrome .

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Stress in Minnesota Jack Rabbits

In a 1939 study also reported inThe Bulletin of the Atomic Scientists, Minnesota JackRabbits demonstrated rise andfall in population densities but when death rates and densitieswere high, they frequentlyentered into convulsive seizuresor comatose states.

Liver and adrenal pathology, aswell as hypertension andhypoglycemia associated withadrenal stress syndrome ,were observed.

Source:http://homestudy.ibea.com/wildlifeID/043jackrabbit.htm

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Population Density andBehavior (Norway Rats)

Calhoun conductedseveral experiments

involving both aquarter-acreenclosure and 6’ x 6’interconnecting

pens. Calhoun made the

followingobservations:

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

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Behavior changes in females

1. Pregnancies were often abortedthrough miscarriage.

2. Considerable disruption of normalpre- and postpartum maternalbehavior (i.e., failure to buildproper nests, nurse offspring and

transport litters) occurred.3. Up to 25% of estrus females were

so vigorously pursued by males

that they did not survive.

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Behavior changes in males

1. Some animals became hyperactive,constantly fighting.

2. These animals also became hypersexualand lost the ability to discriminateamong estrus and non-estrus females,

 juveniles, and other males.

3. Some became cannibalistic.4. Some became withdrawn, demonstrating

no interest in social interaction.

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Human Population Density

The following slide depicts humanpopulation growth in Europe from an

estimated number of 20 millionpeople in 400 BC to 728 million in2000 AD.

Note that in the last three centuriesor so, the growth curve becomesprogressively exponential orlogarithmic.

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Source: http://wps.prenhall.com

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Population Density and Stressin Humans

 Very few studiesdirectly correlate stressof crowding with

changes in the humanbrain.

Compelling evidencenow available to link

neurological changes inhuman brains toprolonged exposure to

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

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Population Density andStress in Humans (cont.)

These neurological changes may very well beconnected with behavioral changes as well.

For example, crime (which represents a form of 

social pathology) occurs at higher rates in urbanthan suburban areas, but the studies showmixed, non-linear correlations above certaindensity levels.

This may be due to “self -treatment” by some

individuals who feel “crowding stress” whenmoving to less densely populated areas (Regoeczi,2002).

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

resemble the stressful environments of crowdedprisons and concentration camps.

 Yet even under these conditions, there does notseem to be direct linear correlation betweenlevels of crowding and levels of violence (Brooks,2004).

Human physiological changes seem to be much

more closely linked to animal models thanbehavioral ones, although some degree of extrapolation seems reasonable.

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Stress, Hormones, and the Brain 

Once perceived, stress activates thehypothalamus of the brain,

triggering a cascade of hormonesthrough the hypothalamic-pituitary- adrenal (HPA) axis.

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

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Stress, Hormones and Brain: TheHypothalamic-Pituitary-Adrenal

Axis Some neurons in the hypothalamus producecorticotropin-releasingfactor (CRF).

The synapses of these cells

make contact with bloodvessels, sending CRF to theadenohypophysis (anteriorpituitary)

The pituitary then secretesadrenocorticotrophic

hormone(ACTH) causingglucocorticoid release bythe adrenal cortex.

 At the same time theadrenal medulla produces

adrenalin.

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

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What do glucocorticoids(such as cortisol) do?

Glucocorticoids increase blood glucose for the“fight or flight” reaction and thus have short-termbenefits.

Over time, frequent release of theseglucocorticoids adversely affects the hippocampusof the brain (the center of numerous glucocorticoidreceptors).

Normal levels of these steroids maintain normalneuronal function in the hippocampus,

High levels of these steroids, however, adverselyaffect synaptic transmission and actuallyinterfere with glucose uptake by neurons.

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

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Daily changes in cortisolin depressed patients

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

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  Jonathan Seckl’s Conclusions

Both animals and humans may graduallydevelop a stress-related syndrome involving:

1. Excess levels of glucocorticoids

2. Pathological changes in the structure andfunction of hippocampal cells

3. Neuronal death (sometimes)4. Increased numbers of hippocampal

glucocorticoid receptors, making the brainmore sensitive to negative feedback control. This may be one mechanism of action for

certain antidepressant drugs.

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Laboratory Activity: Identifyingthe Brain’s Basic Machinery 

Perform a dissection of the sheep(Ovis) brain according to the

excellent guide presented in thefollowing link to the University of  Scranton Neuroscience Program 

Dissection Guide : Sheep Brain Dissection Guide 

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Learning and Conditioningin 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 isacoelmate (without a bodycavity enclosing the gut).

The planarian worm has anervous system with 2light-sensitive eyespots,cephalic ganglia (“brain”),and 2 parallel longitudinal,

ventral nerve cords.Source:

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

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Learning and Conditioningin Dugesia (cont.)

Materials:

Culture of live Dugesia 

Plastic training maze 6V lantern battery and bell wire

Camel’s hair artist’s brush 

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Learning and Conditioningin Dugesia (cont.)

Protocol:

Separate the Dugesia into two groups: control and experimental .

Place the control animals at the beginning of theT-maze and allow them to move through itrandomly. This will leave a layer of mucus on themaze and facilitate movement by others.

Note the numbers which move left, straightahead, or right when they reach the mazeintersection.

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

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Learning and Conditioningin Dugesia (cont.)

Now repeat the process with theexperimental group:

This time apply an electric shock to thewater, surrounding any worm whichmoves either straight ahead or to theright.

Repeat the experiment over a week’stime in order to observe and record thesuccess of the learning process.

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Learning and Conditioningin Dugesia (cont.)

One variant of this experiment involves . . .

Keeping the animals in the dark and then

exposing them to a bright light as anelectrical shock is administered to thewater;

Then determining the number of trials

required for the worms to recoil as thoughthey were receiving an electrical shockwhen exposed only to the light source.

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Observing the Effects of Stresson Learning in Dugesia 

Worms conditioned to light exposureexperiment (and presumably

stressed after repeated trials) Comparatively tested against

previously trained T-maze worms todetermine possible relationship

between stress of prior conditioningand performance in new trials

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References

Boyer, R.M.,et al. Cortisol secretion and metabolism inanorexia nervosa.NEJM, 294 ( 4),1977.

Brooks, Crystal. Overcrowding and violence in federal

correctional institutions:An empirical analysis. Retrievedfrom http://dspace.library.drexel.edu.

Bresler, Jack B., ed. Human Ecology. Reading,MA. Addison-Wesley.1966.

Calhoun, John. Population density and social pathology.Scientific American . Feb.,1962.

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References (continued)

Cox, Thomas. Black Hills State University. Learning andConditioning Laboratory. PSYC305L. Fall, 2004. Retrievedfrom http://www.bhsu.edu.

Duane, Mary, et al. Inquiry in science using an animalbehavior model. Retrieved fromhttp://www.woodrowwilson.org/teachers/bi/1998/planaria/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.

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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 fromhttp://www.macses.uscf.edu/Research/allostatic/notebook/allostatic. August, 1999.

National Institute of Child Health and Human Development. NIHBackgrounder. http://www.nichd.nih.gov. Sept. 9, 2002.

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References (continued)

National Research Council and National Academy of Sciences.National Sciences Education Standards. Retrieved fromhttp://www.nap.edu/readingroom/books/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 fromhttp://www.ncsociology.org/sociationtoday/v22/crowding.htm.

Seckl, Jonathan R. Glucocorticoids, aging, and nerve cell damage.Retrieved fromhttp://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.

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References (continued)

Spedding, M. and P. Lestage. Synaptic plasticityand neuropathology: New approaches in drugdiscovery. MedSci (Paris). 21:1. Jan., 2005.

United States Dept. of Agriculture. AgriculturalResearch 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.

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Module AssessmentQuestions

1. Describe how the general adaptation syndrome (GAS) may have evolved as anadaptation for survival.

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

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

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

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Module Assessment Questions(II)

5. How is pain perceived, and what makes ita stressor? Distinguish between theperception of “good” and “bad” pain. 

6. What evidence exists to show that highpopulation density can induce stress?

7. What changes are induced in the brainand hormonal system as a result of stress?

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

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Module Assessment Questions(III)

9. Distinguish between allostasis andallostatic load .

10. What similarities and differences exist

between humans and animals in how theyrespond to stress? How would you accountfor both the similarities and differences?

11. What is the hypothalamic-pituitary- 

adrenal (HPA) axis , and how does itoperate?

12. What kinds of chemical substances areinvolved in the perception of stress and