PHTY208 Lecture Notes - Lecture 18: Insulin, Music Therapy, Gas Exchange
Stress and adaptation, activity tolerance and fatigue
• Stress and adaptation
o Stress is a term in psychology and biology
o It refers to the consequence of the failure of an organism to respond appropriately
o Signs of stress may be cognitive, emotional, physical or behavioural.
• Activity tolerance and fatigue
o Physical activity - Process of energy expenditure for the purpose of accomplishing an
effect
o Rest - Inactivity
o Fatigue - Perceived lack of sufficient energy
• Stress response
o Homeostasis
• Definition: the purposeful maintenance of a stable internal environment
• A oditio of euiliiu alae i the od’s iteal evioet
• Physiologic processes opposing change
• Dynamic condition
• Narrow range is compatible with maintaining life
o Stress
• Anything that disupts euiliiu o deads that eeed the od’s ailit to
cope
• Requires psychological, behavioural and physiologic adjustment
• Can have negative health consequences
• A state manifested by symptoms that arise from the coordinated activation of the
neuroendocrine and immune systems (general adaptation syndrome: GAS)
o Adaptation
• The ability to respond to challenges of physical or psychological homeostasis and
to return to a balanced state
o Stressors
• Events or environmental agents responsible for initiating the stress response
• Can be endogenous or exogenous or a mix of both
• Types
▪ Eustress: as stress that is healthy, or gives one a feeling of fulfillment or
other positive feelings
▪ Distress: aversive state in which an animal is unable to adapt completely to
stressors and their resulting stress and shows maladaptive behaviours
o Stages of the General Adaptation Syndrome
• Alarm stage
▪ A generalised stimulation of the sympathetic nervous system and the HPA
(hypothalamus pituitary adrenal) axis resulting in release of catecholamines
and cortisol (stress hormone)
• Resistance stage
▪ The body selects the most effective and economical channels of defence
• Exhaustion stage
▪ Resources are depleted, and signs of wear and tear appear
o Allostasis
• Physiological changes in the neuroendocrine, autonomic and immune system that
occur in response to real or perceived challenges to homeostasis
• CNS: neuronal pathways
▪ Cerebral cortex
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▪ Limbic system
▪ Thalamus
▪ Hypothalamus
▪ Pituitary gland
▪ Reticular activating system
o Neuroendocrine Responses
• Stress response is strongly influenced by the nervous (sympathetic) and endocrine
system
▪ Mobilisation of energy
▪ Sharpened focus and awareness
▪ Increased cerebral blood flow and glucose usage
▪ Enhanced cardio/respiratory function
▪ Redistribution of blood from to brain and muscles
▪ Modulation of immune response
▪ Inhibition of reproductive function
▪ Decrease appetite
• Designed to be a short-term fix to insults to homeostasis
o Hormone responses to stress
• Corticotropin-Releasing Factor
▪ Found in hypothalamus, limbic system and brain stem
▪ Important in ANS activity, adrenal activity, metabolism and behaviour
▪ Induces the secretion of ACTH which stimulates adrenal gland to secrete
glucocorticoid hormones (e.g. cortisol)
• Other important hormone responses to stress
▪ About 10+ other hormones
• Coping and adaptation to stress
o Adaptations to stress
• Mechanisms that evolved for organisms to respond to or modify their
environments, habits, or both to achieve a way of life that is best suited to their
needs
• Feedback mechanisms
▪ Negative feedback
o Adaptive Capacity
• Stressors tend to produce different responses in different persons or in the same
person at different times
• Conditioning factors
▪ Internal
▪ External
• Relative risk for development of a stress-related pathologic process is partially
dependent on these factors
o Factors Affecting Ability to Adapt
• Previous learning/exposure and physiologic reserve
• Time
• Internal: genetic endowment, age, sex
• Health status
• Nutrition (malnourished)
• Sleep–wake cycles (shift workers may have more trouble)
• Hardiness
• Psychosocial factors
o Failure to Adapt
• Failure to adapt to a stressor can result in
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• Emotional disturbances
• Headaches
• Insomnia
• Upset stomach
• Gastric and duodenal ulcers
• Rheumatic disorders
• Cardiovascular disease
• Kidney disease
• Effects of stress
o Stress is meant to last only a short time
• Response is beneficial
o Stress can last for long periods
• Disruptive to physical and mental health
o Acute
• Time-limited and do not recur
o Chronic
• Sustained stress
• Can fatigue and impair
o Reactions to Acute Stress
• Associated with fight or flight
• Facilitation of neural pathways mediating
▪ Arousal
▪ Alertness
▪ Vigilance
▪ Cognition
▪ Focused attention
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Document Summary
Stress and adaptation: stress is a term in psychology and biology. Limbic system: thalamus, hypothalamus, pituitary gland, reticular activating system, neuroendocrine responses. Stress response is strongly influenced by the nervous (sympathetic) and endocrine system. Increased cerebral blood flow and glucose usage: mobilisation of energy, enhanced cardio/respiratory function, redistribution of blood from to brain and muscles, modulation of immune response, decrease appetite. Inhibition of reproductive function: designed to be a short-term fix to insults to homeostasis, hormone responses to stress, corticotropin-releasing factor. Found in hypothalamus, limbic system and brain stem. Important in ans activity, adrenal activity, metabolism and behaviour. Stressors tend to produce different responses in different persons or in the same person at different times: conditioning factors. Internal: external, relative risk for development of a stress-related pathologic process is partially dependent on these factors, factors affecting ability to adapt. Internal: genetic endowment, age, sex: previous learning/exposure and physiologic reserve, time, health status, nutrition (malnourished, hardiness, psychosocial factors.
