Exam #1 Flashcards
The stress response is ___________
adaptive
- can be beneficial; helps organisms adapt
Physiological responses are _________________
interconnected
- combination of responses that all affect one another; complex
acute vs. chronic stress
both will have different outcomes
What factors affect stress?
environmental & perceptual factors
- things from outside AND inside affect stress
____________ differences exist
individual
- e.g. sex differences
Stress
very vague term
- e.g. environmental condition, human response, emotion, etc.
Stressor
challenging stimulus that causes stress response
Stress Response
physiological/behavioral/cognitive/emotional response to stressor(s)
Taylor’s definition of stress
- negative emotional experience
- accompanied by a physiological response
- physiology helps respond to stressor
OUTDATED
Lazarus & Folkman definition of stress
Mismatch between personal resources and environmental demands
- e.g. a lot to get done with few resources
Stressor characteristics that affect response
- frequency, intensity, duration
- positive/negative consequences
- controllability
- relevance to life goals
Perceptual characteristics that affect response
- anticipation, perseveration
- sense of control (real or imaginary; YOUR sense of control)
- appraisal (harmful, threatening, challenging)
3 Major Physiological Systems
- Sympathetic Nervous System
- Hypothalamic Pituitary Adrenal Axis
- Immune system
Sympathetic Nervous System
- involves catecholamines (e.g. adrenaline)
- heart rate/blood pressure increase
Hypothalamic Pituitary Adrenal Axis
- involves hypothalamus, pituitary, and adrenals (above kidneys; cortisol)
- hypothalamus gets input from higher brain areas
- CNS -> PNS
Immune System
- complex system of cells to attack non-self (bacteria, viruses, etc.)
Nervous system <—–> Immune system
- (NS): noradrenergic innervation affects antibody production
- (IS): products affect brain activity
Nervous system <——> Endocrine system (HPA)
- (NS): perception of threat leads to release of cortisol
- (ES): thyroid hormones are necessary for development of nervous system
Endocrine system (HPA) <——> Immune system
- (ES): cortisol release inhibits responses
- (IS): immune system products modulate endocrine responses to infection
Function of physiological stress response
- generic ‘emergency response:’
-> useful for both threats and opportunities
-> ‘umbrella system’ - activation of multiple systems
stress response - short-term energy
- increase short-term energy availability
-> increased oxygen
-> increased glucose availability
-> increased circulation and blood shunted to muscles
-> increased cooling (sweat)
-> increased cognitive attention and acuity
(- decrease inessential functions (digestion, sex))
Evolution of stress response
- natural selection favors traits that are adaptive
-> stress response is important for basic survival - strong selection pressure for a generic ‘emergency response’ system (highly conserved across species)
- selection for complex regulation - to minimize costs
- selection of stress physiology occurred generations ago, under different environments
Engineering Analogy of Stress
- used in 1600’s
- considered the body to be a “machine”
Hooke’s Law of Elasticity
- related to engineering analogy of stress
a. ‘LOAD’ - external demand (~stressor)
b. ‘STRESS’ - specific area affected (~stress response)
c. ‘STRAIN’ - shape changed (~allostasis/allostatic load)
Mind-Body Connection
- late 1800’s
- nervous energy can affect health - no obvious organic cause (e.g. fatigue/anxiety without ‘pathology,’ hysteria, neurasthenia)
Psychosomatic Medicine
- 1900’s
- mind and body are ONE
- health = psychological and somatic
- focused on how thoughts, cognitions, and emotions potentially affect your biology and stress
Homeostasis
- Claude Bernard (late 1800’s)
-> physician (M.D.) - physiologist - internal environment must remain constant (steady state) while external environment changes
- external disruptors to internal steady state
- stress response is to keep us at homeostatic setpoint
Emotions, Homeostasis, and Health
Walter Cannon (early 1900’s)
-> experimental physiologist (M.D.)
-> specialized in GI tract, emotions, and hormones
- built on Bernard’s homeostasis
-> goal of body: maintain stable internal environment
-> STRESS RESPONSE: return body to ideal setpoint
- hormonal responses help organisms respond to emergencies
-> hormones travel in blood - affect many organs simultaneously
-> Cannon realized that the stress response has to include a hormonal signal
- Patients’ emotions are important
-> internal disruptors of steady state
Sample Cannon Experiment
- animals exposed to stimuli that prompted an emotional response (e.g. cat sees dog = fear)
-> take blood samples
-> drop of blood on a muscle strip collected from another animal
-> the muscle was attached to coils that measured contraction of muscle - Adrenaline/epinephrine = muscle contraction
-> amount of contraction may indicate amount of adrenaline present - RESULT: epinephrine response to emotional stressor
General Adaptation Syndrome
Hans Selye (1900’s)
- medical doctor (M.D./Ph.D.) - endocrinologist
-> specialized in sex hormones (ovaries), adrenal glands, pancreas
Suite of physiological responses
General Adaption Syndrome (Selye)
1. gastrointestinal ulcers (SNS)
2. adrenal enlargements (HPA)
3. thymic and lymphatic involution/shrinking (immune)
-> if Selye saw one response, he saw ALL three (known as a triad/SYNDROME)
- non-specific response - different stressors, same response
Timeline of responses
General Adaptation Syndrome (Selye)
A. Alarm - activation of response
B. Resistance - plateau/maintenance
C. Exhaustion - wear & tear
How could Selye have performed the experiment better?
- He was essentially poisoning the animals with hormones on the side that created the generic response
- Should have used a control and injected the chemicals he used in the formula (this would have shown him that the formula was the problem)
- formalin
Richard Lazarus (late 1900’s)
- psychologist (Ph.D.) - cognition/emotions
- stressor appraisal affects ability to cope
-> demands vs. resources
Allostasis
Sterling & Eyer (1988)
- psychologists
- build on homeostasis concept
- ‘set-point’ can change to adapt to demands:
-> e.g. repeated stress -> blunted stress response (adaptation)
Allostatic Load
McEwen & Stellar (1993)
- neuroscientists/physiologist (Ph.D.)
- allostatic load
-> ALLOSTASIS: change set-points with conditions
-> LOAD: wear and tear on body from long-term allostasis (e.g. exhaustion)
SNS
- seconds
- telephone analogy: specific communication connections
HPA axis
- minutes
- radio analogy: general broadcast (in blood), receivers (on cells)
- maintain energy and recover from sympathetic response
Immune System
- minutes -> days
- telephone/radio analogy: specific connections and general broadcasting
Vegetative Nervous System
- “autopilot,” primitive
- BRAIN STEM: involuntary actions (HR, breathing)
- RETICULAR FORMATION: bridge brain and body
Limbic Nervous System
- emotions, homeostasis
- THALAMUS: ‘central relay station’ – cortical input
- HYPOTHALAMUS: ‘emotion control’ controls:
-> appetite, body temp, pain/pleasure, threat response - PITUITARY GLAND: ‘master gland’ – controls other glands
-> stimulated by hypothalamus
-> stimulates other glands by releasing hormones into blood - NEOCORTEX: sensation, thought
-> decode sensory info (e.g. threat vs. non-threat)
-> highly developed in humans
-> analysis, imagination, organization, creativity, intuition, logic, memory
-> can override limbic and vegetative responses
Peripheral Nervous System
- separated into somatic and autonomic
Somatic Nervous System
- part of peripheral nervous system
- voluntary actions
- connects to skin and skeletal muscles
Autonomic Nervous System
- part of peripheral nervous system
- primarily involuntary actions
-> e.g. circulation, temp, regulation, digestion, respiration - connects to internal organs
- activated by hypothalamus
- balance of 2 systems: sympathetic/parasympathetic
Sympathetic Autonomic Nervous System
- fight or flight
- rapid metabolic increase
- catecholamine release:
-> epinephrine/adrenaline
-> norepinephrine/noradrenaline
Parasympathetic Autonomic Nervous System
- relaxation
- energy conservation
- decrease metabolic activity
- acetylcholine release (important in memory formation)
Sympathetic Nervous System
- “fight or flight”
- connects to every part of the body, unlike parasympathetic
Causes of SNS
- increased heartrate rate and vasoconstriction (increased blood pressure)
- bronchodilation and increased respiratory rate (increased oxygen to skeletal muscles)
- decreased salivation
- peristalsis
- pupil dilation
- piloerection (hairs on end)
Parasympathetic Nervous System
- “rest and digest”
- PROACTIVE ENERGY CONSERVATION: aids in digestion, supports restorative and resting processes
Causes of PNS
- decreased heart rate
- vasodilation (decreased blood pressure)
- increased salivation
- increased gastrointestinal tract tone and peristalsis
- pupil constriction
Steps in CNS stress pathway
THALAMUS -> AMYGDALA -> HYPOTHALAMUS -> PITUITARY -> HIPPOCAMPUS -> ADRENAL
Thalamus
- center of brain
- amplifies signals from cortex
- integrates sensory information
Amygdala
- important for threat perception/fear
- if damaged, fail to recognize danger
- amygdala activity stimulates hypothalamus
Hypothalamus
- center for fight-or-flight reaction
- links nervous system to endocrine system
Pituitary
- ‘master gland’
- orchestrates important physiological responses:
-> stress
-> growth
-> reproduction
-> lactation
-> immune system
Hippocampus
- highly plastic throughout life – new neurons
- helps store memories of threatening stimuli
- involved in HPA axis regulation
-> contains many glucocorticoid receptors - modulated by amygdala
Adrenal Gland
ADRENAL MEDULLA (internal portion): major organ of SNS
- cortisol is produced in CORTEX (endocrine)
- sympathetic neurons synapse in medulla
- sympathetic activation causes release of epinephrine and norepinephrine into circulation
- Epi and NE bind adrenergic receptors on cells – change cellular function
- Epi and NE can be neurotransmitters in synaptic cleft AND hormones in bloodstream
endocrine system primer
- Cascade of secretion responses: brain -> peripheral glands
1. HYPOTHALAMUS - secrets releasing factors
- stimulates pituitary
2. PITUITARY - secretes intermediate hormones
- stimulates peripheral glands
-> e.g. adrenals, testes, ovaries
3. Peripheral gland/organ - secretes final hormone
-> e.g. cortisol, testosterone, estrogen
4. Final Hormone - travels in blood (released from gland)
- binds cells with specific receptor
- alters cell metabolism and gene transcription
5. Negative Feedback - the off switch - receptors for final hormone on hypothalamic and pituitary cells
- decrease releasing factor and intermediate hormone release
-> may not always work correctly
proteins
- type of hormone
- large, lipid-insoluble
- cannot enter cells
- alters cell function
- relatively fast
steroids
- type of hormone
- small, lipid-soluble
- traverses membrane
- alters gene transcription
-> binds to receptor inside cell - relatively slow
Hypothalamic Pituitary Adrenal Axis
- hypothalamus stimulates pituitary with release of CRH
- pituitary releases ACTH into general circulation
- ACTH stimulates adrenal cortex
- adrenal cortex releases cortisol
-> cortisol has “negative” influence on hypothalamus
–> negative feedback
HPA cascade
- CRH (1-2 s.) -> ACTH (~15 s.) -> Cortisol (1-2 min)
1. hypothalamus - releases corticotropin-releasing factor
2. Anterior pituitary - releases adrenocorticotropin hormone
3. Adrenal cortex - releases glucocorticoid and mineralocorticoid hormone
4. Feedback - GC binds glucocorticoid and mineralocorticoid receptors in hypothalamus and pituitary
- decreased CRH/ACTH production
- decr
Hypothalamus
- input from many brain regions
- regulates motivated behavior
-> e.g. feed, growth, sex - CRH neurons in paraventricular nucleus
-> release CRH to basal hypothalamus and pituitary portal circulation
-> stimulate vasopressin and oxytocin release in posterior pituitary - governs pituitary gland with 2 mechanisms:
-> hypothalamic hormones to anterior pituitary
-> hypothalamic neurons to posterior pituitary
Anterior pituitary
- contains hormone-producing cells
- releasing hormones from hypothalamic neurons
- cells release tropic hormones
Posterior pituitary
- contains blood vessels (capillaries)
- spread peptide hormones from hypothalamic neurons
- not a true gland; doesn’t have cells to produce hormones
- releases vasopressin/oxytocin
Adrenal cortex
- glucocorticoids (‘stress’)
-> break down proteins
-> increases blood sugar - mineralocorticoids (salt/water balance)
-> sodium/water absorption
-> potassium production
Adrenal medulla
- epinephrine & norepinephrine
-> stimulates heart, lungs, blood vessels
glucocorticoid receptors
- low affinity
-> i.e. need high GC concentration to see significant binding - widely distributed in brains
-> including cortex, hypothalamus, amygdala, hippocampus - regulates negative feedback during stress response
mineralocorticoid receptors
- high affinity (only need low levels of GC)
- concentrated in hippocampus, hypothalamus, and amygdala
- regulates tonic GC production/signaling
Kinds of immune function
- innate immunity
- cell-mediated
- humoral
innate immunity
- first response (minutes)
- non-specific - attack ALL antigens
- fever & inflammation
-> fever: kill organisms (overheating)
-> inflammation: send cells to injury
cell-mediated immunity
- second response (hours)
- somewhat specialized
-> if same antigen, there will be an accelerated response - cancer & intracellular antigens (e.g. viruses)
humoral immunity
- slowest response (days/weeks to peak)
- specialized
- cell proliferation: attacks specific antigen
- produces antibodies
- antigens in blood & lymph (e.g. bacteria & parasites)
macrophages
- ‘big & dumb’ [innate, cell-mediated]
- large
- engulf (eat) and dissolve antigens
- generalists: attack many antigens (non-self)
- present antigen parts to initiate more targeted response
natural killer cells
- ‘stealth’ [innate, cell-mediated]
- patrol
- attack & destroy many antigens
- generalists: attack tumors & viruses
lymphocytes
- white blood cells [cell-mediated, humoral]
- made in bone marrow
- high-order immune responses
Kinds of lymphocytes
T cells and B cells
T cells
- ‘middle-man’ [cell-mediated, humoral]
- mature in thymus
- specialists:
-> orchestrate immune response - several kinds:
T-helper/CD4+: stimulate B cells, macrophages, CD8+
Cytotoxic/CD8+: patrol and attack infected and tumor cells - chemical communication:
-> interleukins/cytokines: measured from blood
-> interferons
B cells
- humoral
- specialists:
-> recognize one specific antigen
-> produce antibodies to attach to antigen
–> mark antigen for destruction by innate/cell-mediated
MEMORY CELLS: recognize exact antigen for next exposure - used for secondary antibody response
- VACCINES: stimulate B cells activity/learning:
-> inject weak or dead antigens
-> B-cell stimulate antibody production
-> later infection - antibodies already exist
autonomic nervous system
- projects to immune organs (spleen & thymus)
- circulating NE and Epi: increase proinflammatory cytokines
immune cells
- have glucocorticoid and NE/Epi receptors
Inflammation
- interleukins in brain cause hypersensitivity to pain
Interleukin from T-cells
- cause ‘illness behavior’ (fatigue, lethargy)
