HPA Axis Flashcards
What nucleus in the hypothalamus releases CRF?
Paraventricular nucleus (PVN)
Describe the HPA axis
PVN–>CRF–>ant pituitary–>ACTH–>adrenal cortex–>Cortisol
Describe cortisone
HSD converts cortisol to cortisone. Cortisone has a lower affinity for MR. It is abundant in the placenta, which is important because cortisone cannot bind fetal MR. However, with lots of stress you can overwhelm HSD causing cortisol to enter the fetus and mess with its development and PFC
Where is the feedback in the HPA axis?
Cortisol to PVN: GR inhibits, MR enhances
Cortisol to adrenal cortex: Lots of inhibiting GR, MR enhances
GCs effects
- Maintains circadian expression of genes
- Dirunal (daily), ultradian (pulsatility 1hr)
- Do not adapt to shift work
- Prednisone decreases HPA axis and inc likelihood of depression, anxiety, mania/hypomania - Acute effects
- inc glucose, dec insulin, inhibit immune, decrease osteoblast activity, inhibit production and response to gonadotropins, promote emotional and habitual memory and cognition, less declarative and episodic memory and cognition - Chronic: Abdominal fat, metabolic syndrome, immunosuppression, osteoporosis, sexual dysfunction,
PTSD and HPA
PTSD hyper-suppresses HPA
-Most severe upon awakening
What is the dexamethasone administration test
Dexameth provides neg feedback to pituitary to suppress ACTH secretion. This tests measure if there is hyper suppression of GC or hyposuppression
Depression and HPA
Depression hypo-suppresses HPA (ie there is an increase in activity)
Addictive behaviors and HPA
Addiction hyper-suppresses HPA (ie decrased HPA acitivyt). Decreases basolateral amygdala activty
Withdrawal and HPA
Withdrawal from drugs or fatty foods is stressful! Increases HPA activity
High fat foods and drugs and HPA
Dec HPA
CRF
Is not CNS specific
