Stress, anxiety and aggression Flashcards
Definition of stress
‘Physiological reaction caused by perception of aversive or threatening situations’ -Walter Cannon (1871-1945)
Stress facts
- Change that causes physical, emotional, or psychological strain.
- Physiological responses help prepare for ‘fight-or-flight’ situations
- Episodic (single episode/ acutely) or continuous
- Adaptive (without stress, life is quite boring and you need it to keep life interesting), but also harmful.
Physiology of the stress response-SAM system
1- what do threats require?
2- what does SAM stand for?
3- what do the hypothalamus and sympathetic nervous system stimulate?
4- what else is secreted in the brain during stress?
1- Threats require enhanced activity→ need to mobilise energy resources
2- Sympathetic-Adrenal-Medullary (SAM) system
3- Hypothalamus and sympathetic nervous system stimulate adrenal medulla (kidneys) to release the catecholamine transmitters epinephrine (adrenaline) (↑ blood glucose) and norepinephrine (↑ blood pressure)
4- Norepinephrine also secreted in brain during stress
SAM system
- where does it start
- what is the process
- what doe sit aid?
- function of glucocorticoids
It starts in the hypothalamus which is going to stimulate the sympathetic system eventually.
It releases corticotrophin-releasing hormone (CRH) (or sometimes written as CRF). This acts on the anterior pituitary gland and that releases ACTH as well as glucocorticoids and the adrenal cortex.
This helps the kidneys release catecholamine transmitters epinephrine and norepinephrine.
Glucocorticoids mobilise energy stores by inducing the degradation of proteins to free amino acids in muscle, lipolysis in adipose tissue and gluconeogenesis in the liver.
Physiology of the stress response-HPA axis
1- what does HPA stand for?
2- explain the processes that occur
3- where else is CRH secreted?
4- benefit of glucocorticoids?
5- what also decreases?
1- Hypothalamic-Pituitary-Adrenal (HPA) axis
2-
- Paraventricular nucleus of the hypothalamus (PVN) releases the peptide corticotropin-releasing hormone/factor (CRH/CRF)
- CRH stimulates anterior pituitary to release adrenocorticotropic hormone (ACTH)
- ACTH enters general circulation and stimulates adrenal cortex to secrete glucocorticoids (e.g. cortisol)→increases glucose, decrease pain sensitivity
3- CRH also secreted in brain during stress in limbic system
4- Glucocorticoids help the animal survive. Thus in an adrenalectomized rat, a stressful situation may be fatal.
5- pain sensitivity
Stress effects on the brain:
1- what can stress be?
2- what is the hippocampus involved in?
3- impact of chronic exposure to glucocorticoids?
4- what does glutamate reuptake lead to?
1- Stress can be neurotoxic (Sapolsky)
2- Hippocampus= involved in learning and memory
3- Chronic exposure to glucocorticoids destroys hippocampal neurons via decreased glucose entry and
4- glutamate reuptake→ excessive Ca2+ influx and toxicity
Process of glutamate synapses?
Glutamate synapse releases glutamate transmitters which stimulate the postsynaptic neuron. If you stimulate the postsynaptic neuron, you have these receptors that open up (such as AMPA receptors, NMDA receptors, voltage gated calcium channels ect.) and these excite the post synaptic neuron. This kind of excitation can cause an over excitation and cause neurons to pretty much die out. When we’re really stressed, the hippocampus is the area which is going to be affected easily.
Evidence for stress-induced neurotoxicity: Diamond et al. (1999)
- Rat exposed to cat smell and presence for 75 min (this would be stressful for rat)
- Blood glucocorticoids increased compared to the controls in the home cage or in the chamber alone with no cat
- Impaired primed-burst potentiation (PBP; similar to LTP, synaptic strengthening) in hippocampus
- Impaired in spatial task
Evidence for stress-induced neurotoxicity (in higher order primates): Uno et al. (1989)
- Vervet monkey colonies in Kenya
- Have a hierarchical society
- When bottom rank monkeys subjected to continuous stress by upper rank, the following happens:
→ enlarged adrenal glands (excessive (nor)epinipherine production)
→ hippocampal degeneration
Post-traumatic stress disorder (PTSD)
1- meaning
2- when is PTSD likelihood increased?
3- symptoms?
4- triggered by?
5- what type of response?
1- Long-lasting psychological symptoms after traumatic event (e.g. natural disaster, experience of violence) is over
2- PTSD likelihood is increased if the traumatic event involves danger or violence from other people (assault, war)
3- Symptoms= flashbacks, hypervigilance, irritability, heightened reactions to sudden noises, detachment from social activities
4- Often triggered by cues (e.g. helicopter sound) related to traumatic event (e.g. war)
5- Learned, conditioned response
PTSD and brain changes:
- what brain change occurs in combat veterans and police officers with PTSD
- possible risk factor for PTSD?
- possible reason for hippocampus and PTSD?
- Reduced size of hippocampus in combat veterans and police officers with PTSD (Bremner et al. 1995; Gurvits et al., 1996; Lindauer et al., 2005)
- Possible risk factor for PTSD
– Monozygotic twin study from Vietnam war (Gilbertson et al. 2002)
– For the twin that fought in the war (those with PTSD) compared to the one who did not had a smaller hippocampus - Possible reason for hippocampus and PTSD
– Hippocampus plays a role in distinguishing contexts
– Inability in PTSD from detecting threatening vs safe contexts, ‘threat generalisation’
What other brain regions are altered due to PTSD? + explain
Amygdala and medial prefrontal cortex
- Prefrontal cortex (PFC) involved in impulse control and thought to normally inhibit amygdala, involved in emotional expression (Rauch et al. 2006)
- PTSD associated with greater amygdala activation for fearful and happy face compared to controls.
- PTSD associated with reduced mPFC activation for fearful face and higher for happy face compared to controls.
- PTSD-related changes may indicate excessive emotional response and reduced inhibitory control
Shin et al. (2005)
List two PTSD treatments and what brain alterations occur?
Psychotherapy:
eg.
- discuss experience of traumatic event, emotional pain, losses suffered in combat, etc.
- come to terms with the trauma, identify any unhelpful or destructive thoughts (e.g. blaming yourself wrongly)
- come up with action plan (e.g. how to establish positive relationships with others)
Associated with decreased amygdala activity and increased PFC, increased hippocampus activity (Thomaes et al., 2014)
Antidepressants (SSRIs):
Increased hippocampal volume (Bossini et al., 2007; Vermetten et al., 2003)
What is another PTSD treatment?
Exposure therapy
PTSD treatment: exposure therapy
Explain
- Learned associations (cue–stress) play a role in PTSD
- Cue alone induces a fear response conditioned (conditioned because its a learned cue that provokes it)
- If present cue alone, you get conditioned memory response because that memory of the cue and the stress comes back.
What did Pavlov find?
Extinction learning reduces cue responding
conditioning= cue + salient experience (association is being made) → salivating
after conditioning= bell alone → salivating
during extinction= present bell multiple times in the absence of food → eventually salivation lowers/ stops
PTSD treatment: exposure therapy-
1- what does cue exposure therapy borrow principles from?
2- how does exposure therapy work?
3- what can is also be done with?
1- Extinction learning- same idea of present cue in absence of salient experience (stressful experience)
2- Repeated cue presentation over weeks in safe therapy context reduces response to cue (learning of non-threat, reduction of fear/anxiety) - present cue (eg. helicopter) in safe context.You do this multiple times and the conditioned response which is a fearful stressful response is reduced over time.
4- can also be done with phobias/ drug addiction
- definition of anxiety
- elaborate
- definition of anxiety disorder
- Anxiety= apprehensive uneasiness or nervousness over an impending or anticipated ill (Merriam-Webster)
- Normal part of life, unlike stress may not have an identifiable trigger, but some similar responses (faster heartbeat, breathing)
- Anxiety disorder= more intense fear/anxiety inappropriate for circumstance.
example: graduation and uneasiness about the future
Anxiety disorders:
- definition
- due to?
- difference in experiencing between genders
- types?
- Anxiety disorder=more intense fear/anxiety inappropriate for circumstance, more than a temporary worry
- Likely due to cumulative effects of stress, contributes to depressive and substance abuse disorders
- Women more likely than men to experience
- Many types, but panic disorder, agoraphobia, generalised anxiety disorder (GAD), social anxiety disorder have known biological component
Panic disorder:
- meaning
- symptoms
- what factors play a role
- coping?
- Episodic attacks of acute (seconds to hours) anxiety, terror
- Symptoms: hyperventilation- increased breathing (low CO2), irregular heart-beat, dizziness, faintness, fear of losing control and dying
- Cultural factors play a role as Asian, African, and Latin American Countries have lower rates than e.g. USA (American Psychiatric Association)
- Coping with hyperventilation by breathing into a bag (raises CO2)
