W1L2 - Stress & The Brain

Question 1

Define “Stress”? What feelings is it associated with?

Answer 1

Definition:

Stress is a response to a perceived aversive or threatening situation.

Associated with:

Feelings of being overloaded, wound-up tight, tense and worried.

Question 2

Is stress positive or negative?

Answer 2

Both

Positive:

• Exciting, motivating, improving alertness & performance

Negative:

• Harmful for health and function

Question 3

What is a critical component of a stress experience?

What are thrill seekers attracted to?

Answer 3

Critical Component

• Real or perceived lack of control over the stressor
  
  • Complete lack of control is generally negative
• Threat of bad events without control is sufficient

Thrill seekers are often attracted to “calculate risks,” with some but not total control of the risk

Question 4

What are the 3 types of stress. What are the differences.

Answer 4

1.) Acute Stress:

• Single event
• Increased “flight or fight” response > Raising levels of arousal.

2.) Episodic Acute Stress:

• Repeated (but independent) acute stress
  
  • e.g. life chaos, excessive worry about normal events.

3. ) Chronic Stress:
   * Seemingless endless and uncontrollable

Question 5

Why does animal studies of stress allow?

Answer 5

Human studies are correlational or observational (ethics)

Animal studies provide direct measures of effects of different types of stress on biology

Question 6

What is the key brain region in stress? What are the 2 brain systems mediating stress? Explan the process briefly

Answer 6

Acute stress response: Fight or Flight

Hypothalamus (Key coordination centre)

• HPA system
  
  • Cortisol
• Sympathetic Nervous System
  
  • Epinephrine/Norepinephrine

1. Rapid detection of threat in the amygdala
2. Activates hypothalamus
3. Activate the HPA axis and sympathetico-adrenal-medullary pathway

Question 7

Explain the HPA Axis Process

Answer 7

1. Hypothalamus activated (Triggers emotional responses)
2. Pituitary Gland activated
3. Adrenal Cortex activated (Adrenal Gland)
4. Releases cortisol (detected in blood) and adrenaline
5. Increases metabolism, blood flow, HR

Question 8

Explain the different process in acute moderate vs high stress

Answer 8

Moderate

• Aroused & optimal functioning of PFC
• Allow top-down regulation of thought, actions & emotions
  
  • PFC inhibits amygdala

High

• Arousal increases further overwhelming/impairing function of PFC
• Releasing/increasing the influence of emotional responses, habitual action and bodies arousal response
  
  • PFC offline
  • Amygdala dominates

(Inverted-U)

Question 9

What are the 3 effects of acute stress on the brain

Answer 9

PFC

• IC/Substance Abuse
  
  • Weaken PFC mediated inhibitory control to increase substance abuse (Sinha & Li, 2007)

Amygdala

• Memory of stressful events
  
  • Increase amygdala response to increase memory consolidation of stressful events (Cahill & McGaugh, 1996, Roozendaal et al., 2009)
• Fear Conditioning
  
  • Enhance fear conditioning function of amygdala (Rodriguez et al, 2009)

Question 10

What are the 3 effects of chronic stress on the brain (Brain parts)

Answer 10

Impair higher cognitive functions (PFC/Hippocampus)

• Hippocampus (Memory storage)
  
  • Number & strength of neural connections reduces (more cell death & less neurogenesis)
• PFC (EF)
  
  • Number & strength of neural connections reduces

Strengthens “primitive” brain reactions (Amygdala)

• Amygdala (Mood)
  
  • Number & strength of neural connections increases

Question 11

Why does stress increase sensitivity to stress?

Answer 11

• Impaired emotional & memory function
• Reduces flexible emotional processing & reduce separation between memories
• Causes overgeneralization and less capacity cope with new real or potential stressful events.

Question 12

What are the effects of a.) acute and b.) chronic stress on the body?

Answer 12

Release of glucocorticoids (e.g. cortisol) triggers

Acute effects

• Increased energy availability in muscles and breaking down fats & proteins to glucose.

Chronic effects

• Suppress immune system
  
  • ie train drivers that injure or kill people are more likely to suffer illness months later
• High blood pressure
  
  • Increasing stroke & heart attacks
• Reduced fertility

Question 13

Why we evolved to get acute stress?

Answer 13

Acute stress:

• Helps animals to respond to threats to their survival “flight or flight”
• A reactive/reflexive brain might improve survival in immediate danger.

Question 14

Why do we evolve to get chronic stress?

Answer 14

Chronic

• Effects of early stress on an individual are clearly negative – leading to increased antisocial behaviour, aggression and/or social isolation.
• Some have suggested that these sustained changes could prepare an animal/human for similar adversity later in life
  
  • Aggression etc may be advantageous under subsequent social pressure such as physical attacks or competition for scarce resources

Question 15

What factors influence the stress response

Answer 15

Not only lack of control, but genetics and environemntal influences (explains variability)

Question 16

What is PTSD caused by?

What are the factors?

What is it associated with?

Answer 16

Cause

Experiencing or witnessing death/serious harm (actual or threatened) or learning of trauma to loved one

Factors

Both environmental and genetic factors

Associated with

Recurrent dreams, panic attacks &“flash backs”. Individuals with PTSD have poor mental and physical health

Question 17

What are the brain areas associated with PTSD?

Answer 17

• Smaller hippocampus
• Increased amygdala and insula activity to threat
• Reduced ventromedial prefrontal inhibitory activity to threat

Question 18

Stress and Psychiatric Disorders - Depression, SZ/Bipolar, AD

Answer 18

Depression

• Similar brain areas are implicated in chronic stress and depression and while depression is different it is often considered a stress-related disorder

SZ/Bipolar

• Triggers increased severity of symptoms

AD

• Women with serious stressors in middle age more likely to develop memory impairments

Question 19

How does stress affect emotional memory

Answer 19

Glucocorticoid (e.g. cortisol) stimulates NA response in the basolateral nucleus of the amygdala (BLA), enhancing retention of emotional stimuli

Stress hormones (Cortisol and NA) have been associated with greater memory consolidation in animal and humans

Question 20

How does propranolol work?

Answer 20

Propranolol

• Blocks activation of β-adrenergic receptors by NA (NM releases from LC) and adrenal stress hormones (Activate adrenergic receptors in amygdala, essential in fear memory)

Question 21

Are fearful memories permanent?

Answer 21

Not necessarily.

Startle response to conditioned fear reduced in people who had taken propanlol

Question 22

Implications of propanolol

Answer 22

• Memories can be “relearened” without fear response, with intact memory (Implications for PTSD and anxiety-related ocnditions)

Question 23

What is MBSR. How does it help?

Answer 23

MBSR: Mindfulness-Based Stress Reduction

• MBSR found to moderately (compared to controls/placebo) improved depression, anxiety, distress, stress
• May reduce stress by increasing cognitive flexibility and tolerance for uncomfrotable physical stress/anxious sensations (Reduce perception of threat)

Question 24

Explain the brain-behaviour cycle of stress

Answer 24

• Early life stress > “Epigenetic changes’ and lasting biologicla changes >impair decision making and health
• More negative behaviour and life circumstances