Neurobiology of Stress Flashcards
1
Q
stress
A
- A threat, real or implied, to homeostasis
- Can help survival, unless it’s chronic
2
Q
how was stress first identified?
A
- 13th century infant language experiments by King Frederick caused extreme stress, but people didn’t understand it at the time
- 1930’s: Hans Selye coined the term stress (originally “general alarm reaction”): “the non-specific response of the body to any demand for change”
3
Q
eustress
A
“good” stress – defined by
how one perceives the stressor (e.g.
responding with hope/vigor)
4
Q
Selye’s experiments
A
- Injecting ovarian extracts into rats to try and find new hormones
- Symptoms: adrenal cortex enlargement, atrophy of immune tissues, gastrointestinal ulcers
- Injected other stuff (ex. Pituitary, kidney, spleen, formalin, etc.) and got same symptoms
- Stressors he studied: “exposure to cold, surgical injury, production of spinal shock, excessive muscular exercise, or intoxication of drugs”
5
Q
General Alarm Reaction stages
A
- 6-48 hours after injury; Atrophy of organs, loss of muscle tones, fall of body temp, erosions in digestive tract
- > 48 hours after injury; adrenals enlarge, body growth ceases, gonads atrophy, lactation stops (adaptation can occur, with organs returning to normal)
- > 3 months: Loss of resistance -> exhaustion
6
Q
Hans Selye
A
- coined the term stress
- figured out 3 stages in general alarm reaction
- suggested controversial link between stress and illness
- Dedicated his career to understanding the neuroendocrine mechanisms involved in disease
7
Q
why were Selye’s suggestions about stress and illness controversial?
A
- It was difficult to give a precise, universally applicable definition to stress
- Primitive methodologies to validate scientific ideas
8
Q
homeostasis vs. allostasis
A
- Homeostasis: stability of physiological systems that maintain life (systems essential for life must be maintained within a range optimal for current life history stage)
- Allostasis: the active process by which the body responds to daily events and maintains homeostasis (achieving stability through change)
9
Q
glucocorticoids
A
- steroid hormones (produced by endocrine glands, immediately released, not water-soluble, require “chaperones” to move through bloodstream)
- Can affect almost every cell in the body; major functions in metabolism, development, cognition, immune function, and stress
- large category -> subcategories include cortisol (humans) and corticosterone (rats)
10
Q
mechanisms underlying activation of HPA axis
A
Hypothalamus releases CRH -> acts on pituitary gland -> releases ACTH -> acts on adrenal gland -> releases glucocorticoids
11
Q
PVN (Paraventricular nucleus)
A
- 2 types of neurons
- Magnocellular neurons: oxytocin & vasopressin
- Parvocellular neurons: CRH (Corticotrophin-Releasing Hormone)
12
Q
stressor
A
- Anything that knocks an organism out of homeostatic
balance - Events that are threatening to an organism and which elicit
physiological and behavioural, in addition to that imposed by
the normal life cycle
13
Q
pituitary gland
A
- “the master gland”
- produces hormones that control the production
of hormones in other glands
14
Q
adrenal gland (structure and function
A
- Cortex = outer layer; medulla = inner layer
- produces cortisol -> when ACTH is released, it acts on various enzymes to produce cortisol
15
Q
glucocorticoid receptors (2 types)
A
- Type 1: Mineralocorticoid receptor (MR) (first ones bound, like the baseline fullness of a hotel)
- Type 2: glucocorticoid receptor (GR) (second ones to bind, fills up extra empty spaces like hotel guests at a conference)
- Widely distributed in the CNS and periphery
16
Q
negative feedback
A
- the diminution of an effect by its own influence on the process giving rise to it, as when a high level of a particular hormone in the blood may inhibit further secretion of that hormone
- Change in controlled variable eventually leads to that variable being restored to normal (allostasis)
- Ex. thermostat
17
Q
glucocorticoid’s actions: acute stress
A
- Increased heart rate & blood pressure
- Mobilization of energy
- Suppression of digestion, growth, and reproduction
- Modulation of immune system
- Sharpening of cognition
18
Q
glucocorticoid’s actions: chronic stress
A
- Fatigue, myopathy
- Stress-induced cardiovascular disease
- Ulceration, obesity
- Psychogenic dwarfism
- Amenorrhea, loss of libido, and impotency
- Increased disease risk
- Deficit in memory, neuronal death
19
Q
stress and hippocampus
A
- Chronic exposure to corticosterone causes a loss of hippocampal neurons in a similar amount to losses observed in normal aging
- Chronic stress impairs spatial learning (ex. Rats in water maze – inhibited ability to find platform)
20
Q
mice and corticosteroid binding globulin
A
Mice with less globulin are more susceptible to illnesses
21
Q
influence of artificial selection on stress response of Siberian foxes
A
Hormone and neurotransmitter changes -> low stress response
22
Q
primate social hierarchy on stress system
A
- Subordinate males: higher cortisol levels with exposure to stressors (higher blood pressure, increased anxiety, impaired immune function, etc.) -> much higher risk of disease
- Dominate males: low cortisol levels
- These results translate to humans as well: people in lower-ranking positions at their work call in sick more and are more prone to illness than higher-ranking people
23
Q
Sapolsky’s baboons
A
- Studied a troop of baboons, some ate contaminated garbage, wiping out alpha males
- Years later, he saw that the troop was less aggressive, even though there was only one alpha male left who had been exposed to this epidemic
- This shows that the new members and new alpha males were learning that being less aggressive was the way to behave
24
Q
social isolation on stress system
A
- Increases chances for immune disorders
- Supresses immune response
- Induces anxious-depressive-like behaviour
- Impacts progression of disease
- Influences our perception of pain
- Regardless of this, social isolation is still used in jail (Associated with increased suicide rates, psychiatric illness, increased recidivism rates)
25
trans-generational stress: Dutch famine
Women who were pregnant during Dutch famine gave birth to kids with more intense stress responses
