Download Adrenal medulla

The Physiological Stress Response
System – the relationship between
mind & body
The IB Syllabus Says:
We will study: (The effect of psychological stressors (life events, daily hassles &
workplace/occupational environment on physiological health) (we will also look at
gender & cultural differences and stress management here)
We will study: (The interaction between personality/ cognitive style (Type A & Hardy
personality & stress related illness)
Background: The Nervous
System
• Consists of billions of nerve cells (neurons) which
receive and pass on information within the nervous
system
• Miniscule cells (10 bn in the brain alone!)
• Spaced out with little gaps called synapses in between
them
• Fire out chemicals to send information across the
gaps.
• Neurotransmitters = the chemical substances that
allow communication between nerve cells.
The Nervous System
• The CNS (Central Nervous System) includes the brain
and the spinal cord and contains 90% of the bodies
neurons
• The PNS (Peripheral Nervous System) connects the
CNS to the rest of the body – its divided into the Somatic
Nervous system (which transmits information about body
movements and external environment) and Autonomic
Nervous System (which transmits information to and
from the internal organs and glands)
• The endocrine system also works alongside these
Stress
• A common topic – ‘I’m feeling stressed at the
moment’
• Stress – may be a reason for high prevalence
of anxiety and depression, can also make us
more vulnerable to colds and flu
• Stress – not always negative – from an
evolutionary perspective we need stress to
survive but stress can become damaging
Key Terms - What is Stress?
Two ways to define stress:
1)A state of psychological tension and
physiological arousal produced by a
stressor (response to a stressor)
2) The lack of fit between the perceived
demands of a situation and the person’s
ability to cope (This is the transactional
model -most popular model today – and we
will be studying it in more detail) (if one
feels they cannot cope – this leads to
stress)
Key Terms - Stressor
• Something in the environment (such as
exams of work pressure, significant life
events) that produces a stress response in
a person (Selye, 1956)
How does it feel?
• How did you feel just before your exams
last year?
• Where did you feel it?
• How were your emotions?
Background: How Does the Body
Know it Has to Respond?
The body has 2 messenger systems:
1. Nervous System - travels through
neurons (or nerve cells)
2. Endocrine System – hormones
that travel through the blood
The body’s response to stressors
• Two main responses – both involve the adrenal
glands
• Two adrenal glands – just above the kidneys
each one made up from:
• Adrenal cortex & Adrenal medulla: these
release different types of hormones into the
blood stream, and are controlled by two
different pathways which are the
hypothalamic-pituitary adrenal cortex (HPAC)
pathway and hypothalamic-ANS-Adrenal
medulla pathway (H-ANS-AM)
Location of important areas in the bodily response to stress
Relay center
between
CNS and
endocrine
System
Master gland
for releasing
hormones
Controls
The bodies
organs
The two
parts of the
adrenal gland
The hypothalamic-pituitary adrenal
cortex pathway (HPAC)
• Controlled by the hypothalamus and pituitary gland.
• Hypothalamus is a small structure at the base of the
brain
• Pituitary gland ‘master gland’ as it releases many
hormones into the bloodstream
• The HPAC pathway is activated when higher brain
centres evaluate a situation as stressful and instruct
the hypothalamus to release the CRH hormone to
stimulate the release of ACTH from the pituitary gland
• The ACTH travels to the adrenal cortex and triggers the
release of cortisol – a vital part of the stress response –
mobilising energy reserves – heart rate & blood flow
The red arrows show the hypothalamic-pituitary adrenal cortex (HPAC) pathway
Stressor
Higher Brain Centres
(cortex & limbic systems)
Hypothalamus
CRH Hormone
Brainstem
Pituitary gland
ACTH hormone in
bloodstream
Neural control
via autonomic
nervous system
Adrenal cortex
Metabolic
effects on the body
(higher heart rate & blood
pressure to
get oxygen to muscles)
cortisol
In bloodstream
Adrenal medulla
adrenaline and
nor-adrenaline
In bloodstream
The hypothalamic- autonomic nervous
system adrenal medulla pathway
(H-ANS-AM)
• The autonomic nervous system (ANS) is a
network of nerve pathways running from the
lower part of the brain (the brainstem) to the
body’s organs.
Circulatory (blood) system
Heart
Digestive system
Various glands- including the
Adrenal medulla
• The ANS is controlled by the higher brain
structures, especially the hypothalamus
The autonomic nervous
system is
a part of the peripheral
nervous system
that functions to
regulate the basic
visceral (organ)
processes needed
for the maintenance
of normal bodily
functions.
• The role of the ANS is to maintain normal functioning of the
body systems
• e.g. when you run – the muscles need oxygen and energy, so
carbohydrates and fats are converted into sugars and fatty acids
in the bloodstream, and our heart rate and blood pressure
increases
• this is done by the ANS without our conscious control
• To carry out these tasks there are two divisions to the ANS
The sympathetic subdivision
The parasympathetic subdivision
When activated: the body is
Aroused – heart rate and
blood pressure increase,
fats and carbohydrates are
mobilised, digestion slows
down ‘Sympathetic arousal’
Gets us ‘pumped up’
Stimulates the fight or flight
response
Heart rate and blood pressure return
to normal (decrease), d
igestion speeds up – calm
and bodily relaxation.
Phew – danger over, calms us down
again
The divisions of the Autonomic Nervous System
‘pumps up’
‘calms down’
• The adrenal medulla is controlled by the
ANS – and activation of the sympathetic
branch triggers the release of hormones:
• Adrenaline– well known arousal hormone
• Nor-adrenaline– has similar effects
• they increase heart rate and blood
pressure – preparation for ‘fight or flight’
In stressful Situations the hypothalamus
activates
BOTH the HPAC and hypothalamic-ANS-Adrenal
medulla pathways
The green arrows show the hypothalamic-ANS-Adrenal medulla pathway (H-ANSAM)
Stressor
Higher Brain Centres
(cortex & limbic systems)
Activates
The ANS sympathetic
subdivision
Via the brainstem
Brainstem
Hypothalamus
CRH Hormone
Pituitary gland
ACTH in
bloodstream
Neural control
via autonomic
nervous system
Adrenal cortex
Metabolic
effects on the body
Cortisol
In bloodstream
Adrenal medulla
Adrenaline and
Noradrenaline in
Bloodstream (increases heart
Rate & blood pressure)
The thin arrows show the
hypothalamic-ANS-Adrenal
medulla pathway (H-ANSAM)
(colour in green)
Activates
The ANS sympathetic
subdivision
Via the brainstem
Brainstem
Stressor
Higher Brain Centres
(cortex & limbic systems)
The thick arrows show
the
hypothalamic-pituitary
adrenal cortex (HPAC)
Pathway (colour in red)
Hypothalamus
CRH Hormone
Pituitary gland
ACTH in
bloodstream
Neural control
via autonomic
nervous system
Adrenal cortex
Metabolic
effects on the body
(higher heart rate & blood
pressure to
get oxygen to muscles)
cortisol
In bloodstream
Adrenal medulla
Activity: make your own diagram
Adrenaline and
Noradrenaline in
Bloodstream (increases heart
Rate & blood pressure)
Quick quiz…….
1. Give a step by step account of how the
HPAC stress response pathway is
activated
2. Give a step by step account of how the
H-ANS-AM stress response pathway is
activated
Question 1 mark scheme
1. Gave full definition of abbreviation 1 mark
2. Mentioned higher brain center evaluating
stressor 1 mark
3. Mentions hypothalamus and CRH hormone
triggering pituitary gland 1 mark
4. Mentions ACTH hormone triggering Adrenal
cortex to release cortisol in bloodstream
1 mark
5. Mentions effects of cortisol on body – increase
in heart rate and blood pressure 1 mark
Total= 5 marks
Question 2 mark scheme
1. Gave full definition of abbreviation 1 mark
2. Mentioned higher brain center evaluating stressor 1
mark
3. Mentions hypothalamus and Sympathetic subdivision
of ANS and neural control via brainstem 1 mark
4. Mentions triggering of adrenal medulla to release
adrenaline and nor adrenaline into bloodstream1
mark
5. Mentions effects of adrenaline/nor adrenaline on
body – increase in heart rate and blood pressure 1
mark
Total= 5 marks
Models of stress
•
Selye (1956)– administered ‘noxious’
agents to rats and he found that they had
same physiological response
•
Selye (1956) Called this ‘General
Adaptation Syndrome’ (GAS)
Activating the body’s stress
response
• Selye (1956) identified the HPAC & hypothalamic-ANSadrenal medulla (H-ANS-AM) pathways as the main
components of the body’s response to stressors
• He then thought about why they become activated
• Both systems prepare the body for energy expenditure
• Cannon (1914) called this the ‘FIGHT OR FLIGHT RESPONSE’
‘Fight or flight’
• We have evolved from early humans – 10,000 years ago
– and are behaviour is still adapted to that environment.
• E.g. you see a Sabre toothed tiger – if not hunting – run
for your life, if hunting attack
• Same response – higher brain centres in the cortex and
limbic system perceiving and evaluating the situation
• Leads to the HPAC and hypothalamic-ANS-adrenal
medulla pathway (H-ANS-AM) activation
• Then when the emergency is over systems return to
normal functioning
Fight or Flight Response
Increase
oxygen intake
Release stored
glucose
Divert resources
away from
digestion
Ready to expend energy,
either by fighting or by running away
Fight or Flight
• Fido enters the classroom looking for trouble, you
have 2 choices – run or take him on… For either
of these options what would you need?
• Energy!!!!
The Fight or Flight Response = the reaction of the
nervous system in response to a stressful
situation that produces energy to prepare the
body extended and demanding amounts of effort
The Fight or Flight Response
• An early evolutionary adaptation that is useful in
dealing with physical threats
• Helps us deal with short-term problems that can be
solved by fighting or running
• Unfortunately, many of the threats we face in our
society do not fall into these categories…
• in the modern world, most of the threats in today’s
word a psychological, but dealing with these can
trigger off the same response in the body as an
attacking predator - so we become prepared for
physical action with nowhere to go – this can have
damaging effects in the long term
The General Adaptation Syndrome
(GAS) (Selye, 1956)
• The GAS has three phases
• 1st phase – The alarm phase, the presence of a
stressful event is registered – could be a threat
from an outside or physical stressor – such as
an injury or illness affecting the body - the
hypothalamic-pituitary adrenal cortex (HPAC)
pathway and hypothalamic-ANS-Adrenal
medulla pathway (H-ANS-AM) prepare the body
for energy expenditure (fight or flight) –
nowadays many of the stressors are
psychological
The General Adaptation Syndrome
(GAS) (Selye, 1956)
• 2nd phase is resistance – the body’s stress
response is fully activated and coping with the
stressor, so from the outside things appear to be
back under control
• The 3rd phase of exhaustion if the stressor is
long lasting and chronic. Hormone levels are
depleted, and stress related conditions such as
raised blood pressure, ulcers, depression and
anxiety may develop as stress systems become
exhausted
The three phases of the General Adaptation Syndrome (GAS) (Selye, 1956)
Phase 1: Alarm
Stress response systems activated
(HPAC & Hypothalamic ANS pathways)
Phase 2: Resistance
Body copes with stress
Phase 3: Exhaustion
Stress related illness may develop
Evaluation points?
Evaluation of GAS
• Experimental support – first systematic attempt to
explain the body’s response to stress based on
experimental data – also the first to emphasise the
role of the hypothalamic-pituitary adrenal cortex
(HPAC) pathway and hypothalamic-ANS-Adrenal
medulla pathways
• Use of non human animals – Research carried out on
rats, using physical stressors. Differences between the
physiology of rats and humans, so its difficult to
generalise his work to humans, however, his later
work was done with humans
• Individual differences- GAS ignores individual
differences, e.g. Type A behaviour (Highly driven
people who thrive in stressful situations). It assumes
that we all respond the same way to stress, but
personality and gender can also play role
Questions on stress:
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What's the difference between the central and the peripheral nervous system?
Give a definition of stress
What is a stressor?
How does it feel to be stressed?
What are the two main messenger systems of the body?
What is the name of the model which explains stress stress that Selye (1956) introduced?
What are the names of the main pathways involved in the stress response?
When is the HPAC pathway activated?
Explain how the HPAC stress response pathway works.
What are the two divisions of the ANS?
What are the different roles of these two divisions?
Explain how the H-ANS-AM pathways works.
Complete your own physiology of stress diagram, clearly showing the HPAC and hypothalamicANS-Adrenal medulla (H-ANS-AM) pathways and explain them to each other (use colours/etc)
What is the name of the researcher who developed this model for stress?
When faced with a stressor, the body prepares for energy expenditure, Cannon (1941) called
this the........or..............response
Why is the fight or flight response activated?
What does the fight or flight response do to your body?
What are the three phases of the general adaptation syndrome response to stress?
Explain each of the GAS stages in detail
Make 2 evaluative points that relate to the GAS model of stress?