Neurobiology of Mood Disorders Flashcards
what is the appetitive system
functions to mediate seeking and approach behaviours (inc pleasure)
= the reward system
what parts of brain does the appetitive system involve
mesocorticolimbic dopaminergic regions:
ascending dopamine systems (dopaminergic pathways)
mesolilbic/ cortical projections (ventral striatum)
dorsal striatum (movement)
amygdala (conditioning/ learning)
anterior cingulate (attention/ conflict/ response selection)
orbitofrontal cortex (relative reward preference/ rule learning)
what is the aversive system
functions to promote survival in the event of threat (fear/ pain)
what parts of brain does the aversive system involve
ascending serotonin systems NA/ CRF/ peptide transmitters central nucleus of amygdala hippocampus periaqueductal gray matter
what is the main neurotransmitter in anxiety
serotonin
explains why serotonin is involved in the aversive system
what is the neurobiology of depression
-an altered sensitivity/ accuracy of brain systems evaluating rewards and cues predicting reward within the environment
what is the neurobiology of anxiety
-altered sensitivity/
accuracy of the brain systems evaluating threat and cues predicting threat within the environment
what is the typical course of unipolar depression
peaks at end of high school, early adult hood, old age
when do you usually get mixed states in bipolar disorder
in later life
what endocrine/ metabolic disorders can influence mood disorders
thyroid dysfunction
kidney/ liver dysfunction
what do adverse life events do to ‘depression threshold’
lower, make it more likely to get it
what is the role of neurotransmitters in depression
NT deficiency hypothesis:
- serotonin
- norepinephrine
- dopamine
- GABA
neurotransmitter excess hypothesis
- acetylcholine
- substance p
- corticotrophin releasing hormone
how does neurotransmitter excess cause depression
is toxic
causes chronic inflammation which causes changes in the pathways in the brain
what does decrease serotonin cause
serotonin mediated endorcine responses blunted
associated with depression
what does decreased norepinephrine cause
angeria
anhedonia
decreased libido
what does GABA do
principle neurotransmitter mediating neural inhibition
what do antidepressants do to GABA receptors
upregulated
what causes decreased serotonin
decrease in receptor binding in cortical and subcortical regions
reduction in reuptake sites
what role does the HPA axis play in depression
is upregulated and negative feedback controls are down regulated
CRF is hypersecreted which causes increased ACTH release from pituitary
ACTH causes release of cortisol from adrenal glands
cortisol receptors become desensitised which causes increased activity of pro inflammatory immune mediators and disturbances in neurotransmitter transmission
(decreases neuronal connections so decreases the threshold for anxiety)
how do corticosteroids affect serotonin
reduce hippocampal 5-HT1A receptor sites (5-HT1A plays a big role in how 5-HT communicates with rest of brain)
what causes depletion of norepinephrine
Adverse childhood experiences can produce an over-active responsiveness in this system that persists into adulthood
Seems hyperactive but since there are fewer noradrenergic neurons, this can lead to a deficiency
In situations that most people may not find too stressful, the vulnerable depressed individual does feels very stressed and may deplete NE
what does depletion of dopamine cause
Mesolimbic dopaminergic system is involved in the control of motivation and rewarding experiences
Hypofunction of the dopamine system has been proposed as an underlying brain mechanism of the loss of pleasure/interest experienced in depression
explain the neurotransmitter and mania hypothesis
Deficient serotonergic neurotransmission has been hypothesized as a factor in mania AND depression. Perhaps because it contributes to GABA deficit (NT inhibitor)
gaba deficiency has been linked to mood instability
increased NE and DA activity may underlie mania
what happens to blood flow to pleasure areas of the brain in depression
decreased
