Stress, HPA Axis, and the Hippocampus Flashcards
Define stress
Real/interpreted threat to physiological/psychological integrity of individual - that results in physiological/behavioural responses
Name the 2 pathways to trigger a stress response
Systemic stressor
Psychogenic stressor
What is a systemic stressor and how does it trigger a stress response?
Physical injury/exertion
Direct monosynaptic relay to PVN - via brainstem and hypothalamus
What is a psychogenic stressor and how does it trigger a stress response?
Time-pressured task/interpersonal conflict
Indirect multisynaptic relay from cortex to PVN - via limbic system - processing
What are the 2 phases of the stress response and what do they involve?
Sympathetic NS response - fast, short-term, NA release, adrenaline release
HPA response - slow, long-term, cortisol release
What are the steps of the HPA axis?
Stress
PVN parvocellular neurons - release CRH (into blood), AVP (into anterior pituitary)
Anterior pituitary - releases ACTH
Adrenal cortex - releases glucocorticoids
What is the effect of glucocorticoid receptor activation?
Inhibits release from PVN
What are the fast effects of glucocorticoid and mineralocorticoid receptors?
Modulate glutamate release
Activate endocannabinoid system
What are the slow effects of glucocorticoid and mineralocorticoid receptors?
Modulate gene transcription
What are the characteristics of glucocorticoid receptors?
Low affinity
High capacity
Unoccupied in basal state
Occupied after stress response
What are the characteristics of mineralocorticoid receptors?
High affinity
Low capacity
Occupied in basal state
What is the circadian rhythm of HPA axis activation?
Ensures adequate corticosterone level for normal circadian activity
What is the ultradian rhythm of HPA axis activation?
Pulsatile release of corticosterone - coordinates various organs
What is the Yerkes-Dodson law?
Stress modulation of spatial memory follows inverse-U curve
What is the relationship between stress and hippocampal synaptic plasticity?
Inverse-U
What is the effect of chronic stress on the hippocampus?
Decreases hippocampal LTP
CA3 dendritic atrophy
Decreased spines and NMDAR expression
Which brain area facilitates the stress-enhancement of memory?
Amygdala
Where do the slow stress response and fast stress response take place?
Slow - hippocampus
Fast - amygdala
What is the effect of chronic stress on the amygdala?
Increases amygdala plasticity
