Unit 3 Psychology
Area of Study 1: How does the nervous system enable psychological functioning?
Key knowledge: Dot point 7
“Models of stress as a biological process with reference to Selye’s General Adaptation Syndrome of alarm reaction (shock/counter-shock), resistance and exhaustion, including the ‘fight-flight-freeze’ response and the role of cortisol.”
Stress as a biological process
When a person encounters a stressor, the body initiates a stress response.
Stress response: a set of physical and psychological responses that are automatically triggered as a result of sympathetic nervous system activation following the perception of a threat.
The stress response is designed to assist a person in adapting to the changing environment to aid survival.
There are physiological and psychological effects of stress, including the activation of the fight-flight response.
Physiological responses to stress / Psychological responses to stressShort term stress
- Sympathetic nervous system is activated (fight-flight response)
- Release of adrenalin
- Increased heart rate / Prolonged arousal
- Frustration, depression, anxiety, tension, irritability, anger and aggression
- Difficulty focusing attention and concentrating
- Thoughts dominated by stressors
- Confusion, forgetfulness, difficulty problem solving or making decisions
- Changes to sleeping patterns may lead to tiredness
- Changes to eating habits
- Negative feelings, feelings of powerlessness
- Withdrawal from social contact
- Harmful behaviours (drug abuse, excessive exercise, etc.)
Prolonged arousal
- Increased heart beat which leads to heart palpitations/ damage/disease
- Ulcers
- Strokes
- Weakened immune system (more susceptible to illness)
- Skin irritations
- Fatigue
The role of Cortisol in the Stress Response
When a stressor is first encountered, the immediate response is the activation of the sympathetic nervous system which stimulates the release of adrenaline.
Adrenaline is a short term measure and if the stressor remains for an extended period of time, the body cannot keep releasing adrenaline.
When the stressor remains and we are stressed over a pro-longed period (pro-longed arousal), the HPA Axis stimulates the secretion of cortisol.
The HPA Axis maintains activation of the sympathetic nervous system for an extended period of time.
H = Hypothalamus, P = Pituitary Gland, A = Adrenal Gland (adrenal cortex)
The hypothalamus stimulates the pituitary gland. The pituitary gland secretes the hormone ACTH into the bloodstream. The ACTH travels to the adrenal cortex and stimulates the release of cortisol.
Cortisol: a hormone that energises the body by increasing energy supplies such as blood sugar and enhancing metabolism. Cortisol also acts as an anti-inflammatory.
Cortisol also has negative effects as it slows tissue repair and weakens the immune system. Pro-longed arousal (stress) can therefore cause a person to be susceptible to illness.
‘Fight-flight-freeze’ Response
When the body encounters a threat (stressor) it activates the sympathetic nervous system, which initiates the ‘fight-or-flight’ response.
Fight-or-flight response: an automatic, involuntary response that aids survival by preparing a person to defend (fight) against a threat, or escape (flight) a threat.
There is also another response that can occur when a threat is perceived. This is the ‘freeze’ response and it is initiated by the parasympathetic nervous system.
Freeze response: a response to a threat whereby we feel so helpless to deal with it that we become immobilised in its presence due to the activation of the parasympathetic nervous system overriding the sympathetic nervous system.
The parasympathetic nervous system causes the heart rate to slow, blood pressure to drop, muscles lose their tension and the body stills (tonic immobility). In the frozen state it is not possible to vocalise (speak) and right before the freeze the head and eyes ‘orient’ themselves (turn towards) the threat.
The freeze response occurs when fight or flight will not aid survival. By ‘playing dead’ an animal may have an opportunity to escape when the predator is not paying attention, or fool the predator into losing interest.
In some instances people and animals may faint, which assists in avoiding pain and lower blood pressure can also restrict blood loss through wounds.
Once the threat is passed, or there is an opportunity to escape, the body can quickly transition back into fight-flight mode and the energy conserved in the freeze is used to escape.
Fight-flight-freeze response: an involuntary, physical response to a sudden and immediate threat (or stressor) in readiness to: confront and fight off the threat, escape the threat, or keep absolutely still and silent, avoiding the threat.
*Videos
**Student Activity Manual – 2.3, 2.6
Hans Selye – General Adaptation Syndrome (GAS)
Hans Selye considered stress to be a non-specific physiological response caused by any demands placed on the body by either pleasant or unpleasant conditions. As a result of his studies, Selye developed a model of stress which he called the General Adaptation Syndrome (GAS).
The GAS is the body’s typical response pattern in terms of resistance to stress over time.
The stages of the GAS are; alarm reaction (shock and counter shock), resistance and exhaustion.
Stage 1: Alarm reaction
The first stage of the GAS, where resistance to stress first drops below normal, then increases above normal.
Comprised of two sub-stages: shock and counter shock.
Shock – the first sub-stage of alarm reaction in the GAS, where resistance to stress drops below normal and the body acts as though it is injured; blood pressure and body temperature decrease.
Counter shock – the second sub-stage of alarm reaction in the GAS, where resistance to stress rises above normal levels due to the activation of the sympathetic nervous system.
Stage 2: Resistance
The second stage of the GAS, where the resistance to stress remains above normal levels; cortisol is released to help repair the damage caused by stress on the body.
Following the alarm reaction stage, if the stressor has not been defeated, the body enters the stage of resistance as it attempts to stabilise its internal systems and fight the stressor. The ‘stress hormone’ cortisol is released into the bloodstream to help combat the negative effects of stress on the body. This energises the body to assistance in resisting the stressor, however it weakens the immune system. Other processes not necessary to fighting the stressor such as digestion, growth and sex drive stall, menstruation may stop and production of testosterone decreases.
Although the body is better able to cope with the initial stressor, because physiological arousal remains higher than normal, the ability to resist additional stressors is significantly lowered. So, the body puts all its resources into fighting the current stressor, but may not have any resources to fight additional stressors.
For example: studying for VCE Exams. The student may be able to study despite less sleep, poor diet and lack of exercise, however, after the exam they may develop a cold and the body is unable to fight this additional stressor.
Stage 3: Exhaustion
The final stage of the GAS where the body’s resources are depleted and its resistance to stress falls below normal levels.
If we are unable to defeat the original stressor during the first two stages, we reach a stage of exhaustion, in which the body’s resources are drained and the stress hormones that triggered the fight-flight response are depleted. This leaves us vulnerable to additional stressors such as infection and disease and we may succumb to illness. Prolonged arousal weakens the immune system making us more susceptible to disease
The exhaustion stage is characterised by extreme fatigue, symptoms of anxiety and depression, nightmares and physical illnesses such as hypertension, digestive problems and heart disease. The ‘wear and tear’ on the body caused by the prolonged state of arousal weakens the immune system and the body’s ability to maintain homeostasis.
· Studies of psychoneuroimmunology show that there is a relationship between stress and disease. Stress does not cause disease; it just makes an individual more susceptible.
· Psychosomatic illnesses are physiological symptoms that are experienced as a result of psychological stressors.
Strengths and limitations of the GAS
Strengths / Limitations· Contributed to the concept of stress as it relates to physical and mental health
· Further developed awareness of link between stress and disease
· Identified biological processes associated with the body’s stress response
· Identified the body’s limited resources that can be depleted through the three stages of adaptation to a stressor / · ‘One size fits all’ model does not take into account individual differences in physiological responses to a stressor
· GAS places too much emphasis on adrenal cortex and endocrine system in the stress response, when other bodily systems are involved as well
· Different stressors trigger different hormonal responses (stress response is not uniform)
· Environmental and biological factors are not adequately explained to identify differences in individual stress responses
· Not all people experience the same physiological reactions to chronic stress
· Selye’s model is primarily based on results from studies into animals which may not be applicable to humans
*Student Activity Manual – 2.4, 2.5
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