Neurobiology of Mood Disorders

Question 1

what is the appetitive system

Answer 1

functions to mediate seeking and approach behaviours (inc pleasure)
= the reward system

Question 2

what parts of brain does the appetitive system involve

Answer 2

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)

Question 3

what is the aversive system

Answer 3

functions to promote survival in the event of threat (fear/ pain)

Question 4

what parts of brain does the aversive system involve

Answer 4

ascending serotonin systems 
NA/ CRF/ peptide transmitters 
central nucleus of amygdala 
hippocampus 
periaqueductal gray matter

Question 5

what is the main neurotransmitter in anxiety

Answer 5

serotonin

explains why serotonin is involved in the aversive system

Question 6

what is the neurobiology of depression

Answer 6

-an altered sensitivity/ accuracy of brain systems evaluating rewards and cues predicting reward within the environment

Question 7

what is the neurobiology of anxiety

Answer 7

-altered sensitivity/

accuracy of the brain systems evaluating threat and cues predicting threat within the environment

Question 8

what is the typical course of unipolar depression

Answer 8

peaks at end of high school, early adult hood, old age

Question 9

when do you usually get mixed states in bipolar disorder

Answer 9

in later life

Question 10

what endocrine/ metabolic disorders can influence mood disorders

Answer 10

thyroid dysfunction

kidney/ liver dysfunction

Question 11

what do adverse life events do to ‘depression threshold’

Answer 11

lower, make it more likely to get it

Question 12

what is the role of neurotransmitters in depression

Answer 12

NT deficiency hypothesis:

• serotonin
• norepinephrine
• dopamine
• GABA

neurotransmitter excess hypothesis

• acetylcholine
• substance p
• corticotrophin releasing hormone

Question 13

how does neurotransmitter excess cause depression

Answer 13

is toxic

causes chronic inflammation which causes changes in the pathways in the brain

Question 14

what does decrease serotonin cause

Answer 14

serotonin mediated endorcine responses blunted

associated with depression

Question 15

what does decreased norepinephrine cause

Answer 15

angeria
anhedonia
decreased libido

Question 16

what does GABA do

Answer 16

principle neurotransmitter mediating neural inhibition

Question 17

what do antidepressants do to GABA receptors

Answer 17

upregulated

Question 18

what causes decreased serotonin

Answer 18

decrease in receptor binding in cortical and subcortical regions

reduction in reuptake sites

Question 19

what role does the HPA axis play in depression

Answer 19

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)

Question 20

how do corticosteroids affect serotonin

Answer 20

reduce hippocampal 5-HT1A receptor sites (5-HT1A plays a big role in how 5-HT communicates with rest of brain)

Question 21

what causes depletion of norepinephrine

Answer 21

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

Question 22

what does depletion of dopamine cause

Answer 22

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

Question 23

explain the neurotransmitter and mania hypothesis

Answer 23

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

Question 24

what happens to blood flow to pleasure areas of the brain in depression

Answer 24

decreased