Anxiety and Fear Flashcards
Why do we have fear and anxiety responses?
To avoid harm through hypervigilance, increased arousal and avoidance
What do anxiety disorders (ptsd, gad, ocd etc) have in common?
- patients with anxiety disorder will have features of other disorders
- many of the anxiety disorders respond to similar treatment - exposure, cbt, SSRI benzodiazepine
- Little evidence to show that different disorders stem from different regionso f the brain
What hormonal changes occur during anxiety?
Changes in releasing hormones -. affect pituitary hormones and ultimately the peripheral hormones. testosterone levels drop and the rest increases.
Main culprits of anxiety (proposed)?
- Cortisol
- Amygdala
- PFC
- Hippocampus
- Norepinephrine
- BDNF
- HPA axis
What is Kulver Bucy syndrome?
Kluver Bucy syndrome is a rare behavioral impairment characterized by inappropriate sexual behaviors and mouthing of objects. Other signs and symptoms, include a diminished ability to visually recognize objects, loss of normal fear and anger responses, memory loss, distractibility, seizures , and dementia
How is life threatening stimulus processed?
- eyes to thalamus to cortex (at the same time point 2 is happening)
- eyes to thalamus to amygdala
- amygdala sends to muscles, sympathetic nervous system and hypothalamus.
- person jumps even before consciously knowing why
What evidences show that memories are stored in amygdala?
- LTP can be induced in amygdala
- Protein synthesis inhibitors injected directly into amygdala will prevent the formation of fear conditioning
- chronic stress will induce increased dendritic branching in the amygdala
Why are traumatic events so persistent?
- Fearful experiences form quickly in amygdala (due to structure changes and memory formation)
- Enduring memories reside in neocortex and amygdala
PFC and anxiety?
Rational reappraisal (gaining control) is required to reduce anxiety.
Which part of the PFC is well connected to amygdala?
Medial PFC including anterior cingulate gyrus
What evidences highlight the role of mPFC in anxiety?
- Lesions of PFC in rats reduce the ability to extinguish fear
- Stimulation of the mPFC inhibits a learned fear response: rats don’t show anxiety
- Subjects with anxiety disorder have reduced activities in mPFC
- mPFC lights up in fear fmri studies in healthy subjects
Smaller hippocampus volume was correlated to the susceptibility of getting PTSD
NIL
What do barbiturates, ethanol (alcohol) and benzodiazepines do
Bind to GABA receptors (aminobutyric acid) -> activating them results in calming the brain (too much results in sluggish and even coma)
Norepinephrine and anxiety?
- Too much norepinephrine neurons with cell bodies in locus coeruleus (in pons, related to stress and panic).
- Norepinephrine neurons projects to amygdala and increased release when stress
- Also stimulates the release of corticotrophin releasing hormone (CRH) and activates HPA Axis.
- Peripheral norepinephrine produces somatic symptoms like increased heart rate, sweating etc
BDNF and amygdala?
- BDNF transcription is increased in amygdala after fear conditioning
- BDNF absent from hippocampus -> rats unable to extinguish conditioned fear
- in PFC controls fear memory formation and fear extinction
