31 Stress and Fear Flashcards
Define stress from a neuroendocrine perspective.
a state of homeostatic dysregulation produced by aversive stimulus causing activation of the HPA axis
What is allostasis?
process by which systems deal with changes in set point due to severe or prolonged stress (adverse result)
Name 3 factors that will determine the effect that stress will have on an individual.
chronicity, percieved controllability, physical v. psychological stressors
Acute stressors activate which brain system(s) (neuro-endocrine system) ?
HPA (hyothalamic-pituitary-adrenal) axisis the main neuroendocrine system mediating stress response, specifically mediated by the paraventricular nucleus
Why is PVN’s anatomical position optimal for its function?
PVN receives lots of converging information from both cognitive and visceral sources and then sends output to primarily the HPA axis but also the locus coeruleus and its parallel stress response system
What effect does the PFC have on stress?
PFC “dampens” recruitment of PVN but specifically for psycological stress (dampening is not as prominent with physical stress)
Describe the pathway of HPA which is transiently activated in response to stress.
PVN is stimulated and produces CRH which stimulates the anterior pituitary to create ACTH and the adrenal to produce glcocoritcoids
How is the stress response usually transient?
negative feedback of glucocorticoids on the hypothalamus
In what sense does PVN generate “good” stress?
stress response by HPA promotes a survival response in the transient sense
What are the effects of moderate and excessive levels of glucocorticoids in learning and memories.
moderate levels aid learning and memory, excessive levels are neurotoxic (hippocapus); chronic or unpredictable stress can cause increased cortisol which can lead to depression
How is fear related to stress?
fear is considered a subset reaction within stress, an extreme stress response
How is the amygdala important in stress and fear?
amygdala is the main neural site mediateing fear responses (is part of the limbic system anterior to the hippocapus)
Is the amygdala a unifed structure or an arbitrary grouping of heterogenous nuclei?
it is a collection of heterogeneous nuclei that function together, these nuclei include basolateral complex (cortical-like), central neuclei (autonomic system) and cortical and medial nueclei (part of olfactory sytem- direct connection)
What is the CRF system?
a collection of extrahypothalamic sites that make CFR but work independently; CFR works independently from but parallel to ((complements) the HPA axis
Contrast lesion and stimulation of the amygdala.
lesions lead to Kluver-Bucy syndrome or Urbach Wiethe (loss of fear), stimulation of the amygdala potentiates fear
What are the 3 F’s and what is ther significance?
fight, flight and freeze which are survival responses to stress
What can happen if your glucocorticoid levels are chronically elevated?
excessive fear or stress can contribute to etiology of depression and other psychiatric illnesses by allostatically altering the systems that regulate normal adaptive stress/fear responses (baseline levels of cortisol are elevated)
Name 5 characteristics of stress that may lead to likely hood of developing depression.
repeated/chronic, unpredictable, uncontrollable, intense and interaction with underlying genetic vulnerability (may be important especially during developmental periods such as childhood)
What types of fear may be helpful to understanding depression?
overly intense expression fo fearful behavior, regular expression of fearful behavior in an inappropriate contex (other symptoms include anhedonia, psychomotor retardation and ingestive disruption)
Chronic psycological stress causes neuronal atrophy in the ______, as demonstrated by studies with tree shrews.
hippocampus (impovershed dendritic arbors)
T/F Psychological stress attenuates normal neurogenesis (# cells) in adult hippocampus.
TRUE
What was the notable observation from learned helplessness experiements on rats?
rats that had control over their stress and those without stressor showed similar response while rat with stress showed decreased appetite, loss of body weight, decreawed motor actiivty, sleep disturbances and behavioral dispair *** as well as changes in monoamines like norepi, serotonin and dopamine
Patients with depression have chronic overactivity within the ______
amygdala
What are 4 paradigms that are used to measure fear/anxiety in animals?
potentiated startle, approach-avoidance, defensive burrying and freezing
