Lecture 10 Flashcards
What is stress?
Effects of factors that act on the body to increase energy consumption above basal level.
What is an stressor?
A stressor is anything that throws the body out of homeostatic balance.
What is the stress response?
A series of physiological and behavioral responses that serve to re-establish homeostasis.
Homeostasis
It is the process by which the body maintains a relatively constant internal stability
Allostasis
Achieving stability through physiological or behavior change (stress-specific)
Describe the Allostatic load?
The cumulative cost incurred by the body during allostasis (chronic stress effects)
Two endocrine responses to stress?
Two endocrine systems involved:
Epinephrine (adrenaline) from adrenal medulla
First respondent and it is FAST.
Glucorticoids from adrenal cortex.
Effects of norepinephrine NE in response to stress
Release from locus coeruleus (to brain)
stimulates alertness
From the adrenal medulla to blood to activate vasoconstriction
From sympathetic spinal cord to target organ
What is caused by Epinephrine EP in response to stress
Loss of senses (hearing, tunnel vision)
Inhibition of digestion. Increase of HR/Respiration. Vasoconstriction and dilation of large skeletal blood vessels. Dilation of pupils and bronchioles and production of glucose from glycogen. Does not cross Brain Blood Barrier (BBB)
Glucocorticoids and stress
Good candidates for mediating the behavioral effects of stress. They are released in response to different stressors and can easily cross the BBB- epinephrine does not. GR (receptors) are found in the brain.
Short term effects of the release of cortisol during stress
Stimulates gycogenolysis. Suppresses some immune functions and inflammatory responses. Enhances learning and NE release.
what are other hormones involve in stress response and what are their response?
Vasopressin: Increases blood pressure and aggressive behavior
Β-endorphin: Inhibits pain sensation
Prolactin: Suppresses reproduction
H-P-G Axis activation during normal response
Normally, low levels of prolactin stimulates testosterone production.
H-P-G Axis activation during stress response
Under stress, high levels of prolactin make Lydig cells insensitive to LH AND potentiates negative feedback loops
Adaptive effects of the stress response (fight or flight)
EP increases energy, glucocorticoids, O2 consumption and decreased blood flow to systems not required for escape. Opioids and canabinoids decrease pain perception. High glucose levels increase Sensory function and memory.
General Adaptation Syndrome
The process of coping with stressors. Consists of three stages: Alarm reaction, Resistance and
Exhaustion
What are the effects of Acute and Chronic stress in a individual
Acutely, stress is an adaptive response that allows the individual to survive
Prolonged stress shifts this useful, adaptive response to a pathological condition
Chronic Stress Inhibits wound healing.
Effects of Prenatal Stress in Humans
Decreased birth weights, developmental delays. Attentional deficits, hyper-anxiety, impaired social behaviors and possible increased of schizophrenia.
Prenatal glucocorticoid effects
Low birth weight, adult cardiovascular and metabolic disorders. Hypertension. Insulin resistance. Hyperlipidemia. Ischemic heart and brain disease. Behavioral problems in childhood.
Exposure to exogenous glucocorticoids
Rats stressed or exposed to exogenous glucocorticoids in utero have decreased hippocampal GR, which may lead to impaired HPA negative feedback.
Neonatal Maternal Separation (stressor)
Model of early-life stress. Neonates are removed from dams daily from postnatal day 1-21. 15 min separation has no effect
3 hour separation has reduced hippocampal neurogenesis. 24 hour separation: In Adults
elevated HPA axis response to stress
Increased anxiogenic-like behavior
Psychosocial Dwarfism
Rare condition, observed in humans raised with little or no social contact. it is characterized by:
Lack of growth and development. Disruption of normal sleep cycles. Disruption of normal GH secretion. Lack of responsiveness to GH
Recover when placed in an environment where social and physical contact are available
Stress and Reproductive Dysfunction
Reproductive behavior is suppressed in response to stress
Stress is a major contributing factor to sexual dysfunction and infertility in humans.
Stress and Reproductive Dysfunction in Males
Stress inhibits testosterone synthesis
Reduces sexual motivation and performance.
Stress and Reproductive Dysfunction in Females
In animals, litter size and birth weight are inversely proportional to corticosterone levels. In humans, functional hypothalamic amenorrhea (cessation of menstruation) have elevated cortisol levels
Sex Differences in stress response
Female rats have higher basal levels of corticosterone than males.
In response to stress, females show higher levels of ACTH and corticosterone. This difference is activated by estrogens, Orvariectomy in adults eliminates sex difference, estradiol replacement restores it.
Post-Traumatic Stress Disorder
Result of intensely stressful events Severe behavioral (flashbacks, nightmares) and hormonal responses to stress and endocrine disregulation. Low basal levels of cortisol may predispose an individual to PTSD. Associated with reduced hippocampal volume
Stress and sex in males
Stress impairs male sexual function by suppressing testosterone
Via actions at GnRH and LH
Stress and sex in females
Stress effects female reproduction by inhibiting GnRH and LH and increasing testosterone.
Effects of exposure to chronic stressor in rats
After 2 days: Adrenal ctx hypertrophy. Reduced immune response. Atrophy of thymus, spleen, lymph nodes.
2 weeks: No apparent symptoms
2 months: Death
Cardiovascular Effects of stress
Parents who lost a child show an increase in myocardial infarction (heart attack) starting 6 years after death (especially SIDS)
