Autonomic Nervous System (18) Flashcards
What is the ANS?
> The motor subdivision of the PNS that controls the body’s automatic activities
Composed of specialised group of neurones that regulate cardiac muscle; smooth muscle in the walls of visceral organs; blood vessels; glands
Homeostasis depends largely on the workings of the ANS
Also called “Involuntary Nervous System”
What are the divisions of the ANS?
> Sympathetic and parasympathetic
> Act together to keep the body running smoothly
What is the parasympathetic nervous system?
> 'Rest and Digest' > Keeps body energy use low > Most active when body is at rest and not threatened > Involves the 'D' activities- digestion, defaecation and diuresis > e.g. person relaxing after a meal: - BP, HR and RR low - GI tract activity is high - Warm skin and constricted pupils
What is the sympathetic nervous system?
> ‘Fight or Flight’
Most active when we are in emergency/ threatening situations
Involves ‘E’ activities- exercise, excitement, emergency and embarrassment
Promotes adjustments during exercise- blood flow to organs reduced, and flow to muscles is increased
e.g. when person is threatened:
- HR increases, breathing rapid and deep
- Skin cold and sweaty and dilated pupils
What is the ‘Fight or Flight’ mechanism?
> Provides optimal conditions for an appropriate response to threat, whether that is running, seeing more clearly or thinking more critically
Pounding heart, rapid deep breathing, dilated pupils, changes in brain wave pattern, changes in galvanic skin resistance
Vasoconstriction in cutaneous (skin) and visceral (internal organ) blood vessels
Vasodilation in myocardial and skeletal muscles
Nutrients mobilised from liver (glycogen) to raise glucose levels
Non-essential activities such as GI and urinary motility are reduced
What is the definition of stress?
‘A situation where demands on a person exceed that person’s resources or ability to cope’- Stress management society
What is involved in the stress response?
> Includes intellectual, behavioural and emotional components, decision making, withdrawal and anger, major part is physiological
CNS
Hypothalamus
Sympathetic nervous system
Anterior and posterior pituitary gland
Adrenal medulla (A and NA) and adrenal cortex (cortisol)
What is eustress?
> A certain amount of stress is good as it acts as a motivator and can enhance performance
What is eustress?
> A certain amount of stress is good as it acts as a motivator and can enhance performance
What is distress?
After a certain point, stress has a negative effect and our performance drops off
What is distress?
After a certain point, stress has a negative effect and our performance drops off
What is distress?
After a certain point, stress has a negative effect and our performance drops off
What can understanding stress lead to?
> Identifying individuals at risk of inability to deal with stressors
Recognition of how prolonged/ repeated stress can result in disease
Understanding of how the neuroendocrine component of the stress response can eventually become a threat to health
What is the acute response?
> Short-lasting
Initiated by sympathetic nervous system activity and secretion of catecholamines (A, NA and dopamine) from the adrenal medulla
What is the slow stress response?
> Longer-lasting (slower to start and slower to dissipate)
> Caused mainly by action of glucocorticoid hormones from the adrenal cortex
What are 3 theories of stress?
1) Stress as a stimulus (Cox 1978)
2) Stress as a transaction (Lazarus 1966)
3) Stress as a response (Selye 1956)
What is Selye’s theory?
> Concerned with bodily psychophysiological responses to environmental stressors
Sources of stress can be environmental or social and they can be exogenous (outside) or endogenous (inside)
‘Stress is the non-specific response of the body and that freedom from stress is death’
Developed concept of the General Adaptation Syndrome (GAS) to discuss the 3 stages of stress- alarm reaction; resistance stage; exhaustion stage
What is the alarm stage?
> Predominantly initiated and controlled by the sympathetic nervous system
Affects visceral motor organs such as the brain, heart and skeletal muscles
Initial sympathetic effects are prolonged by simultaneous release of catecholamines
Effect of alarm stage is a short-term homeostatic control to enable adaptation/coping
Progress (returning to homeostasis) depends on person’s perception of stress, duration of the demand and their coping mechanisms
What is the resistance stage?
> Controlled predominantly by the endocrine system, especially hypothalamus
We have limited amount of adaptation energy and every stressor leaves signs of ‘wear and tear’
Homeostasis is restored- if adaptation energy is depleted, may move into next stage
What is the exhaustion stage?
> Signs of alarm stage reappear as adaptation energy runs out and homeostasis fails
Stress related illnesses appear
Selye describes; diseases of adaptation leads to death
What are some physical indicators of stress?
> Hypertension > Tachycardia > RR increases > Loss of appetite > Insomnia > Nausea
What are some behavioural indicators of stress?
> Poor work performance > Forgetfulness > Social isolation > Loss of interest > Smoking/alcohol
What are some emotional indicators of stress?
> Crying > Irritability > Hostility > Anxiety > Depression
