The Physiology of Stress - stress pathways (SAM & HPA axis)

Question 1

what is stress

Answer 1

The subjective experience of a lack of fit between a person and his or her environment (e.g. where the perceived demands of a situation are greater than a person’s perceived ability to cope).

Question 2

what is the Sympathomedullary Pathway

Answer 2

The sympathomedullary pathway (fight or flight response) is thought to be an innate, evolutionary-determined response to threatening situations

Question 3

what is the hypothalamus

Answer 3

The hypothalamus lies at the base of the brain.
It is involved in many of the body’s physiological functions, such as stress-related arousal, hunger, thirst and sexual and reproductive behaviours.
It regulates many of these functions automatically.
If the cortex and limbic system identify a stressful situation of threat or danger, then the hypothalamus is stimulated to activate one of the stress pathways.

Question 4

Acute (short-term) stress and the Sympathomedullary pathway

Answer 4

Immediate (acute) stressors arouse the autonomic nervous system (ANS) – the response is fast!

It is called autonomic because it governs itself i.e. heart beat, blood pressure, body temperature.
The ANS governs the release of hormones (chemical substances which circulate in the blood).

Question 5

The Autonomic Nervous System (ANS)

Answer 5

ANS centres are located in the brainstem. Pathways run down the spinal cord and are distributed throughout the body by spinal nerves.
It has two separate divisions: the sympathetic branch and the parasympathetic branch.
Nerve fibres from both branches connect with internal structures such as various glands e.g. the adrenal medulla.

Question 6

The SYMPATHOMEDULLARY (SAM) PATHWAY

Answer 6

1)Hypothalamus detects stressor/threat

2)Arousal of the Autonomic Nervous System (ANS) (Sympathetic branch)

3)SNS stimulates the Adrenal Medulla…

4)…which releases Adrenaline and Noradrenaline

Question 7

Release of adrenaline results in…..

Answer 7

Sweatiness
Increased heart rate and raised blood pressure
Diverts blood away from the skin
Breathing quickens and becomes shallower
Increases blood supply/oxygen to the brain (for rapid response planning) and skeletal muscles (for physical action)
Pupil dilation
Digestion slows down, to conserve resources for fight/flight.

Question 8

what does adrenaline also trigger

Answer 8

Adrenaline also triggers the release of blood sugar (glucose) and fats into the bloodstream, supplying energy to the muscles to enable the individual to fight or flee the threatening situation.

Question 9

what is the parasympathetic branch of the ANS

Answer 9

The parasympathetic branch of the ANS returns heart rate and blood pressure to normal, as well as speeding up digestion, helping the body to relax.

Question 10

Chronic (persistent) Stress and the Hypothalamic Pituitary-Adrenal (HPA) System

Answer 10

1)Hypothalamus (part of the brain)
stimulates the release of corticotropin-releasing factor (CRF),
which travels to….

2)the Pituitary Gland
(master gland, resistance to stress and
disease, bodily growth)
- secretes adrenocorticotropic hormone (ACTH)

3)Adrenal Cortex

4)Release of Corticosteroids/Cortisol

Question 11

Evaluation of the Stress Pathways

Answer 11

:)This biological explanation of stress allows accurate, objective measures to be made.
- For example, stress hormones can be measured in urine samples.

:)People who have had their adrenal glands removed have to be given hormone supplements to help them cope with stressors, highlighting the importance of the SMP, HPA system and stress hormones in responding to stress.

Question 12

Briefly outline what is meant by the ‘tend-and-befriend’ response observed in females.

Answer 12

During our evolutionary past this would have involved protecting themselves and their young through nurturing behaviours (tending) and forming protective alliances with other women (befriending)

Question 13

Why might females have evolved to have a different system for coping with stress?

Answer 13

This may be because their responses evolved in the context of being the primary caregiver of their children.
Fleeing too readily at any sign of danger would put a female’s offspring at risk – they would be left defenceless, reducing reproductive success.

Question 14

What is the name of the hormone thought to inhibit a fight-or-flight response in females?

Answer 14

Oxytocin

Question 15

What effect is oxytocin thought to have on behaviour?

Answer 15

Oxytocin is thought to increase relaxation and nurturing, reduces fearfulness and decreases the stress response characteristics of the fight or flight response.

Question 16

what did Taylor(2000) suggest

Answer 16

research by Taylor (2000) suggests that males and females respond in different ways to stress, with acute stress producing the ‘fight-or-flight’ response in males and the ‘tend-and-befriend’ response in females.

Question 17

why are the HPA and SAM systems gender-bias

Answer 17

the standard descriptions of the HPA and SAM systems are arguably gender-biased (towards how males respond to stress) and not applicable to females, particularly as studies on human stress responses have mainly been conducted on males - researchers were concerned that fluctuations in hormone levels as a result of the menstrual cycle could act as a confounding variable, leading to varied stress responses, thus reducing the validity of the data.

Question 18

Furthermore, most of the research into the sympathomedullary pathway is animal-based.
This presents extrapolation issues.
Why might the stress responses observed in animals fail to represent how humans respond to stress? Are there any specific factors that you can identify that set animals and humans apart in terms of how they respond to stressful situations?

Answer 18

Humans are more likely to have a cognitive element to their stress responses i.e. an individual’s thoughts and their interpretation of the situation determine whether there is a physiological response or not.

Question 19

research suggests that cognitive appraisal of a situation is crucial in terms of how the individual responds and determines how the body responds, which neither of the stress pathways acknowledge
why?

Answer 19

the individual’s thoughts (cognitions) and their interpretation of the situation determine whether there is a physiological response or not.

Question 20

what did Lazarus and Folkman (1984)

Answer 20

Lazarus and Folkman (1984) developed the transactional model to explain the role of cognitive appraisal in stress responses, explaining how an individual’s assessment of the demands of the situation (‘perceived demands’) and their perceived ability to cope determine whether or not the sympathomeduallary pathway is activated.

If there is a mismatch between the perceived demands and the individual’s perceived ability to cope, then the sympathomedullary pathway is more likely to be activated.

Question 21

Explain the type of stress that leads to the secretion of the stress hormone cortisol

Answer 21

Chronic or persistent stress e.g. workplace stress

Question 22

What is the name of the stress system that is activated when this type of stress is experienced?

Answer 22

The Hypothalamic Pituitary-Adrenal (HPA) System

Question 23

How does cortisol help your body to deal with this type of stress and why wouldn’t adrenaline be sufficient enough?

Answer 23

Cortisol is a glucocorticoid hormone, permitting a steady supply of blood sugar, providing individuals with a constant source of energy, allowing the body to deal with more persistent stressors.
Adrenaline, on the other hand, just provides an immediate source of energy.

Question 24

What are some of the known positive effects of the hormone cortisol?

Answer 24

Helps the body to cope with a stressor
Lower sensitivity to pain

Question 25

However, research has suggested that cortisol can also have damaging effects on the body…
in which ways

Answer 25

weight
immune system
cardiovascular system

Question 26

what do studies suggest about the cardiovascular system

Answer 26

Studies suggest that the high levels of cortisol from long-term stress can increase blood cholesterol and blood pressure, common risk factors for heart disease. This stress can also cause changes that promote the build-up of plaque deposits in the arteries.

Question 27

immune system

Answer 27

Reduced immune system performance – Cortisol produced by the HPA stress response inhibits production of lymphocytes (white blood cells), therefore suppressing the immune system (immunosuppression).

Question 28

weight

Answer 28

Constant release of cortisol may increase your risk of developing insulin resistance, raises your blood sugar, alters your appetite, reduces your ability to burn fat and increases the rate at which you store fat.

Question 29

Prolonged activation of the HPA system, due to lengthy periods of stress, can lead to extended exposure to high levels of cortisol. In extreme cases this can lead to …

Answer 29

…Cushing’s Syndrome.

Question 30

The symptoms of Cushing’s Syndrome include

Answer 30

weight gain, memory and attention lapses, as well as mood disruption.

Question 31

Cortisol has also been found to have a negative effect on cognitive abilities:

Answer 31

Newcomer et al. (1999) found that participants given levels of cortisol high enough to produce blood-sugar levels similar to those of people experiencing major stress events, like abdominal surgery, were poor at recalling prose passages than participants given levels of cortisol only high enough to produce a stress reaction similar to minor surgery, such as having stiches out.
This suggests that stressful stimulation of the pituitary-adrenal system has adverse effects on cognitive abilities such as memory.