Anxiety and Stress Treatment Flashcards
(36 cards)
What is the amygdala and functions?
- series of nuclei
- involved in integrating the fear
response - limbic system
What happens when an amygdala is removed from the brain?
- loss of phobia of spiders
- loss of fear/inhibitions
Key Inputs to the Amygdala:
What is the role of the hippocampus in the regulation of anxiety?
by relating fearful memories to the current context
if abnormal function may generate fear in response to non-threatening stimuli
Key Neurobiological Stress Responses:
Activation of HPA Axis in Fear:
- amygdala activates the
hypothalamus - hypothalamus releases
corticotrophin releasing hormone,
(CRH) which acts on the pituitary
gland - pituitary releases
adrenocorticotropic hormone
(ACTH) which acts upon adrenal
glands - adrenal cortex releases cortisol
- cortisol is a glucocorticosteroid
which will ultimately release
glucose into the bloodstream in
response to the fear
HPA Axis:
Regulation of the HPA Axis:
negative feedback loop
cortisol directly feedback to hypothalamus and pituitary
cortisol acts on the hypothalamus also feedback to control cortisol levels
Activation of the Locus Coeruleus:
- amygdala activates locus coeruleus
- locus ceoruleus activation releases
noradrenaline - fight or flight response
Noradrenaline Pathways:
Amygdala and hippocampus respond to which neurotransmitter systems (3):
- noradrenergic
- serotonergic
- GABA
Noradrenergic Systems that affect that Hippocampus and Amygdala:
- origin
- effect
- originate in locus coeruleus
- increase arousal and anxiety
Serotonergic (5-HT) Systems that affect the Hippocampus and Amygdala:
- origin
- effect
- raphe nuclei
- signals presence of threat
- restrain associated behaviours
GABA System that affects the Hippocampus and Amygdala:
- origin
- effect
- distributed widely through the
brain - reduce anxiety
Noradrenaline involvement in Anxiety:
- increased noradrenaline in
prefrontal cortex found in anxiety
and PTSD - impaired cognitive function
- some adrenergic receptor
antagonists improve stress induced
cognitive impairment
Serotonin and Anxiety:
- arise from raphe nuclei
- drugs increasing serotonin levels
effective in treating both anxiety
and depression (SSRIs)
Serotonin and Anxiety:
Why SSRIs help with balancing pathways?
- noradrenaline increased in stress
- serotonin decreased in stress
- SSRIs increase serotonin in
synapses, hence push the shifted
balance back to normal
Some antidepressant that are effective in depression and anxiety increase reuptake both serotonin and noradrenaline.
Why do they not make people with depression more anxious?
- actions of SSRIs and SNRIs are
complex; delayed onset of action
suggests neuroadaptive changes
eg complicates - baseline activity vs reactivity of
noradrenergic systems - complex array of adrenoreceptors
and actions of these receptors
GABA and Anxiety:
- drugs increasing GABA activity
decrease anxiety - partial agonist: alcohol
- indirect agonist: barbiturates,
benzodiazepines - drugs decreasing GABA activity
increase anxiety - antagonist: flumazenil
- could anxiety be associated with
fewer GABA (A) receptors - endogenous neuromodulator
blocking benzo site at GABA (A)
receptor
GABA and Panic:
- patients with panic disorder have
fewer benzopdiazepine binding
sites - indicates a lack of sufficient
inhibitory control via GABA in
cortical and limbic regions to
suppress inappropriate fear
response and then panic attack
Functional Neuroanatomical Changes in Anxiety:
- amygdala: reduced volume,
hyperactivity - hyperactivity of thalamus
- overactivity of insular cortex in
response to threat - reduced volumes in anterior
cingulate cortex and prefrontal
cortex: areas important for
conscious threat appraisal and loss
of frontal-limbic regulation
processes - hippocampal changes
Chronic Stress and the Hippocampus:
- chronic activation by cortisol
- increases Ca2+ into neurons
- excitotoxicity results in cell
death
- damage to the hippocampus
means it cant feedback to limit
cortisol production - some anxiety disorders may result
from:
- diminished activity of the
hippocampus
- loss of feedback to amygdala
- inappropriate fear response
**reduced hippocampal volume in PTSD and in chronic stress in animals
Microscopically: fewer large pyramidal cells
Neurobiology of PTSD:
