Summary

• Stress: adaptive response to situations that pose demands, constraints or opportunities.
  • Homeostasis: low stress.
  • Stressors challenge homeostasis: stress response.
  • Return to homeostasis: recovery, return to low stress.
  • Or inability to return to homeostasis: exhaustion, chronic stress.
• Stressors: wide variety.
  • Internal, external, short -lived, pro-longed, mild, severe, etc.
  • Common elements: novelty, uncertainty or lack of control.
• Stress response: adaptive processes.
  • Brain: releases adrenaline (short-working) and cortisol (longer working).
  • Body: mobilizes resources and shuts down long-term functions.
• Recovery: return to homeostasis.
  • Threat is removed, cortisol lowers.
  • Adaptive: analabolic processes lead to recovery, restoration and regeneration.
• Exhaustion: inability to return to homeostasis.
  • Inability to cope with or remove threat, prolonged exposure to cortisol.
  • Maladaptive: catabolic processes impair behavior, physiology, mood, memory, thinking, etc.
• Avoid: chronic exposure to stress. 
  • Lack of sleep, lack of exercise and lack of recovery time.
  • Lack of control, lack of routines and familiarity.
• Improve: adaptive capacity, develop resilience.
  • Short-term stressors : physical (exercise), thermal (heat, cold). (“Stres — Sauna“)
  • Vagal tone. (“Stress — Breath Work“) 

Introduction

• Stress is a state of threatened homeostasis
  • Response to situations that pose demands, constraints or opportunities.
• Homeostasis.
  • All body systems are operating smoothly to maintain equilibrium.
  • Stress levels are low.
• Challenge to homeostasis.
  • Stressors: psychological or physical stimuli that trigger a response.
• Return to homeostasis.
  • Adaptive response (general adaptation syndrome or GAS) leads to recovery.

Stressors: wide variety

• Potential stressors.
  • Acute or chronic.
  • Small or traumatic.
  • Real or imagined.
  • Internal or external.
• Common stressor elements:
  • Novelty.
  • Uncertainty.
  • Threat.
  • Lack of control.
• Impact of stressor depends on:
  • Nature of the stressor (psychological, physical, etc.)
  • Nature of person affected (stress tolerance).

Stress Response

• Stressors trigger a switch in body and brain to respond to the threat.
  • Mobilization of energy to maintain brain and muscle function.
  • Sharpened and focused attention on the perceived threat.
  • Enhanced cardiovascular output and respiration.
  • Redistribution of blood flow and energy delivery to the brain and muscles.
  • Modulation of immune function.
  • Inhibition of reproductive physiology and sexual behavior.
  • Decreased feeding and appetite.
• Stress response unfolds in stages.
  • Brain: (pre-consciously) registers a threat.
    • Thalamus: quick and dirty formatting of incoming information.
    • Amygdala: assesses emotional significance.
  • Brain: triggers release of hormones.
    • Hypothalamus: immediate -> triggers release of adrenaline.
    • Hypothalamus: longer-term -> triggers release of cortisol.
  • Body: visceral organs react to deal with threat.
    • Hormones cause body to marshal resources and shut down long-term functions.
• Stress response typically followed by a recovery process.
  • Return to homeostasis.
  • Anabolic reactions trigger restoration, homeostasis and regeneration.

Immediate stress response: adrenaline, fight-or-flight.

• Sympathoadrenal medullary or SAM axis.
  • Regulates the release of adrenalin.
• Autonomic nervous system.
  • Sympathetic nervous system.
    • Fight-or-flight response.
    • Directs energy to bodily systems for acute adaptation to stress.
  • Parasympathetic nervous system.
    • Return to homeostasis.
• Hypothalamus triggers release of (short-acting) adrenaline from adrenal glands.
  • • Mobilize resources (glucose, oxygen).
    • Shut down long-term functions (digestion, reproduction, energy storage).
• SAM pathway:
  • Links the sympathetic nervous system and the adrenal medulla (part of adrenal gland).
  • Activation of adrenal medulla.
    • In response to outside stimuli.
    • Sensory information from the sympathetic nervous system.
  • Release of norepinephrine and epinephrine into the blood.
    • Chemical messengers that act rapidly and dispel quickly.
    • Also called noradrenaline and adrenaline respectively.
    • Drive the “fight-or-flight” response.
    • Increase in heart rate, cardiac output, blood pressure, and glucose levels.
  • Inactivation of adrenal medulla.
    • Return to “rest-and-digest”, homeostasis.

Longer-term response: cortisol, prepare for longer fight.

• Hypothalamic-pituitary-adrenal axis (HPA axis):
  • Regulates the release of cortisol.
  • Prepares the body to cope with and recover from the stressor.
• Reverses the body’s anabolic processes.
  • Stops metabolically expensive functions (digestion, reproduction, etc.)
  • Starts breakdown of energy stores to release glucose.
    • Mobilize pools of fatty acids, proteins, amino acids.
    • Short-term: arousal and sharpened attention.
    • Long-term: anxiety, selective recall, risk aversion.
  • Blocks the effects of testosterone and insulin (growth hormones).
  • Powerful anti-inflammatory.
• HPA pathway:
  • Links the nervous system to the endocrine system.
    • Hypothalamus: part of the limbic brain (emotions, memory).
    • Pituitary gland: a pea-shaped structure located below the thalamus.
    • Adrenal gland: small, conical organs on top of the kidneys.
  • Regulates release of glucocorticoids (cortisol in humans).
    • Starts with corticotropin releasing hormone and vasopressin from the hypothalamus.
    • Stimulates the pituitary to secrete adrenocorticotropic hormone (ACTH).
    • Stimulates the adrenal glands to secrete cortisol.
  • Negative feedback regulation.
    • Terminates response to stress.
    • Shuts down HPA axis.
  • Cortisol receptors are ubiquitous throughout the body.
    • Mobilize energy stores throughout the body.
    • Affect metabolism and immune system.
    • Increase blood glucose, blood pressure, immunological activity.

Three phases of stress response: general adaptation syndrome (GAS)

• Alarm.
  • Mobilization.
  •  Adrenaline.
• Resistance.
  • Coping with the threat.
  • Cortisol.
• Recovery or exhaustion.
  • Recovery:
    • Stressors are overcome or eliminated.
    • Anabolic reactions trigger restoration, homeostasis and regeneration.
  • Exhaustion:
    • Failure to overcome the threat.
    • Catabolic reactions trigger depletion of physiological resources.

Good and bad stress

• Good stress.
  • Enhances function (physical or mental).
• “Optimal” level of stress – adrenaline response.
  • Stimulates delivery of energy, oxygen, synapses, memory retention.
  • Strengthens the immediate stress response.
  • Focuses attention and heighten awareness.
  • Quickly dissipates (minutes).
  • Avoids triggering chronic cortisol release.
• “Optimal” level of stress – cortisol response.
  • How much is released (too much or too little not good).
  • How responsive are you (type of receptors, individual biological set-points).
• Bad stress leads to:
  • Prolonged arousal.
    • No adaptation or coping.
  • Continual activation of stress response.
    • Chronic cortisol exposure.
• Prolonged cortisol exposure is maladaptive.
  • Hampers recovery process.
• Prolonged cortisol negatively affects.
  • Immune system.
  • Behavior, habits:
    • Coping mechanisms (bad dietary practices, lack of exercise, smoking, alcohol, etc.)
    • Increased rewards associated with food, leading to weight gain and further changes in eating habits.
  • Physiology:
    • Physical development.
    • Cognitive function:
      • Less focus, lower concentration.
      • Emotional, less factual thinking:
        • Increases the amygdala: center of emotional significance (fear, anxiety, aggression).
        • Shrinks the hippocampus: memory, factual details.
        • Weakens the frontal cortex: impulse control, long-term planning, empathy.
      • Selective attention to negative memories, rumors, imaginary patterns.
      • Risk aversion.

Controlling the stress response: resilience

• Cycle stress and rest.
  • Balance catabolic and anabolic hormones.
    • Catabolic hormones: short-term metabolic support when challenged.
    • Anabolic hormones: rebuild repleted energy stores.
  • Growth index: ratio of anabolic to catabolic hormones:
    • Measure of immunity to daily stress, state of preparedness.
• Train adrenal response.
  • Repeated short exposure to stressors.
    • Similar to physical toughening: stress-recover-stress-recover.
  • Strong adrenal response avoids excess longer-term cortisol response.
    • Physical stress: exercise.
    • Thermal stress: exposure to cold (weather, water), heat (sauna).
• Develop good vagal tone.
  • Vagus nerve plays a role in calibrating and selecting appropriate stress response:
    • Freeze, fight-or-flight, social engagement.
  • Efficient tool for conserving energy, minimizing stress.
  • Good vagal tone = select proper response = high HRV.
    • Heart Rate Variation.
      • Breathe in, heart rate speeds up.
      • Breathe out, heart rate slows down.
  • Breathing exercises help develop better vagal tone.
• Reduce conditions that bring on stress.
  • Excess novelty: routines and familiarity instead.
  • Avoid lack of control when it matters.
• Develop greater mental and physical toughness.
  • View novelty as a positive challenge, not a negative threat.
    • Issue: very little conscious control.

Stress and sleep

• Stress -> less sleep.
  • Strong connection between sleep and stress:
    • Cortisol is one of the factors that drives wakefulness and sleepiness.
  • Cortisol release normally in line with the circadian rhythm.
    • Spikes in the morning (after waking up).
    • Slow decline throughout the day.
    • Should be relatively low at night.
  • If cortisol is (too) high at night, inhibits sleep.
    • Inhibits the release of melatonin.
    • More difficult to fall asleep, less brain restoration.
  • Chronic stress causes cortisol to stay high throughout.
    • Lower sleep quality.
• Good sleep -> less stress.
  • Sleep increases in growth hormone and testosterone.
  • Sleep reduces metabolism and blood flow.
• Lack of sleep -> more stress.
  • Lack of sleep increases cortisol, heart rate, temperature, oxygen consumption, glucose, etc.
  • Vicious cycle: lack of sleep -> more stress -> less sleep, etc.

Stress and physical activity

• Stress -> less physical activity.
  • Stress impedes physical activity and leads to more sedentary behavior.
  • Although sometimes, physical activity can increase due to stress (coping mechanism).
• Physical activity -> less stress.
  • Physical activity is a stressor.
  • Builds resilience against physical effects of stress.
  • Different types of activity (aerobic, high intensity, daily life) have different types of impact.
  • Less depression, anxiety, cognitive impairments, etc.

Stress and nutrition

• Stress -> bad nutrition.
  • Short term: stress can shut down appetite.
    • Adrenaline triggers slowdown in digestion.
  • Longer term: stress increases appetite.
    • Cortisol triggers greater metabolic demands (more energy, oxygen).
  • Cortisol (+ high insulin) negatively affects nutritional choices.
    • Foods that counter-act stress: high sugar, high fat.
    • Calming influence of immediate serotonin spike.
  • Can also result in over-eating (coping mechanism).
• Nutrition -> lowering stress.
  • Food intake can stimulate level of serotonin.
    • Calming influence (complex carbs, etc.)
  • Food intake can cut levels of adrenaline or cortisol.
    • Vitamin C, magnesium (GABA).

 

Additional reading / listening

• “The Drive with Peter Attia — Robert Sapolsky” (link to summary)
• “The Hour Between Dog and Wolf” (link to summary)