The Fight or Flight Response
Often the endocrine system and the autonomic nervous system (ANS) work in parallel
with one another, for instance during a stressful event.
The fight or flight response is an automatic response that takes place when we are faced
with a real or perceived threat. If we are faced with an acute stressor (immediate
threat/short-term stress) the fight or flight response stimulates the functions of the body
necessary for vigorous muscle activity. It also inhibits the functions of the body that
are not immediately essential for fighting or running.
Definition of the fight or flight response: A sequence of physiological changes within the
body that are triggered when the body prepares itself for defending or attacking (fight) or
running away to safety (flight) in response to a perceived threatening or stressful
situation. This activity involves changes in the nervous system and the secretion of
hormones that are necessary to sustain arousal.
The body’s response to acute (sudden) stressors: The Sympathomedullary Pathway
1. Sudden acute stressor/threat occurs
2. Amygdala in the brain is mobilised (it associates sensory signals with emotions
associated with fight or flight such as fear or anger).
3. Hypothalamus receives distress signal and communicates with the rest of the body
through the...
4. Sympathetic nervous system. Once activated, it sends a signal to the...
5. Adrenal medulla; which responds by releasing the hormone...
6. Adrenaline, into the bloodstream
7. Heart rate and blood pressure increases, breathing becomes more rapid (fight or
flight response increase bodily activities)
8. Parasympathetic nervous system is activated when the threat has passed,
decreasing bodily activities, returning them back down to normal (‘rest and
digest’)
(Remember: Sister Amy Has Some Apples And Hates Peas)
The Sympathetic Nervous System: ‘Fight or SNS Physiological Changes
Flight’
The sympathetic nervous system (SNS) is - Increased heart rate allows for greater
primarily involved in responses that help us to blood flow to skeletal muscles
deal with emergencies, increasing bodily
activities to prepare us for fight or flight.
, - Increased breathing rate (bronchial
The SNS works alongside the endocrine tubes in lungs dilate for greater oxygen
system to bring about physiological arousal intake)
in the fight or flight response (involving the - Adrenal glands (the adrenal medulla)
release of adrenaline into the bloodstream). are stimulated to release adrenaline
- Increased pupil size (dilated) lets
Neurons from the SNS travel to virtually every more light in for better vision
organ and gland within the body, preparing the - Inhibits (stops) digestion
body for the rapid action necessary when the - Sweat glands stimulated to produce
individual is under threat. more sweat
- Inhibits saliva production (dry mouth)
It also slows down bodily processes that are - Glycogen stored in the liver is
less important in emergencies. converted to glucose for energy
- Tenses rectum
The Parasympathetic Nervous System: ‘Rest PNS Physiological Changes
and Digest’
The parasympathetic nervous system (PNS) is - Decreased heart rate
primarily involved in calming the body once - Decreased breathing rate
the emergency has passed. It balances the - Adrenal glands stop releasing
sympathetic nervous system, decreasing adrenaline
bodily activities. - Constricts pupils
- Stimulated digestion
The PNS works alongside the endocrine - Sweat glands constrict
system to return the body to its resting state - Stimulates saliva production
in the rest and digest response (involving the - Relaxes rectum
release of acetylcholine).
Think of it acting like a parachute, slowing
everything back down to normal.
The function of adrenaline: To prepare the body for defending or attacking (fight), or
running away to safety (flight), in response to a perceived threatening of stressful situation.
Physiological effects of adrenaline:
Physiological change Reason
Increased heart rate Greater blood flow to skeletal muscles
Constricts blood vessels, increasing rate of Increase blood supply/oxygen to skeletal
blood flow to the brain and skeletal muscles for physical action and to the
muscles and raising blood pressure brain for rapid response planning
Increased respiration (bronchial tubes in Greater oxygen intake
lungs dilate)
Increased sweating To regulate body temperature
Increased pupil size To let in more light for better vision
Often the endocrine system and the autonomic nervous system (ANS) work in parallel
with one another, for instance during a stressful event.
The fight or flight response is an automatic response that takes place when we are faced
with a real or perceived threat. If we are faced with an acute stressor (immediate
threat/short-term stress) the fight or flight response stimulates the functions of the body
necessary for vigorous muscle activity. It also inhibits the functions of the body that
are not immediately essential for fighting or running.
Definition of the fight or flight response: A sequence of physiological changes within the
body that are triggered when the body prepares itself for defending or attacking (fight) or
running away to safety (flight) in response to a perceived threatening or stressful
situation. This activity involves changes in the nervous system and the secretion of
hormones that are necessary to sustain arousal.
The body’s response to acute (sudden) stressors: The Sympathomedullary Pathway
1. Sudden acute stressor/threat occurs
2. Amygdala in the brain is mobilised (it associates sensory signals with emotions
associated with fight or flight such as fear or anger).
3. Hypothalamus receives distress signal and communicates with the rest of the body
through the...
4. Sympathetic nervous system. Once activated, it sends a signal to the...
5. Adrenal medulla; which responds by releasing the hormone...
6. Adrenaline, into the bloodstream
7. Heart rate and blood pressure increases, breathing becomes more rapid (fight or
flight response increase bodily activities)
8. Parasympathetic nervous system is activated when the threat has passed,
decreasing bodily activities, returning them back down to normal (‘rest and
digest’)
(Remember: Sister Amy Has Some Apples And Hates Peas)
The Sympathetic Nervous System: ‘Fight or SNS Physiological Changes
Flight’
The sympathetic nervous system (SNS) is - Increased heart rate allows for greater
primarily involved in responses that help us to blood flow to skeletal muscles
deal with emergencies, increasing bodily
activities to prepare us for fight or flight.
, - Increased breathing rate (bronchial
The SNS works alongside the endocrine tubes in lungs dilate for greater oxygen
system to bring about physiological arousal intake)
in the fight or flight response (involving the - Adrenal glands (the adrenal medulla)
release of adrenaline into the bloodstream). are stimulated to release adrenaline
- Increased pupil size (dilated) lets
Neurons from the SNS travel to virtually every more light in for better vision
organ and gland within the body, preparing the - Inhibits (stops) digestion
body for the rapid action necessary when the - Sweat glands stimulated to produce
individual is under threat. more sweat
- Inhibits saliva production (dry mouth)
It also slows down bodily processes that are - Glycogen stored in the liver is
less important in emergencies. converted to glucose for energy
- Tenses rectum
The Parasympathetic Nervous System: ‘Rest PNS Physiological Changes
and Digest’
The parasympathetic nervous system (PNS) is - Decreased heart rate
primarily involved in calming the body once - Decreased breathing rate
the emergency has passed. It balances the - Adrenal glands stop releasing
sympathetic nervous system, decreasing adrenaline
bodily activities. - Constricts pupils
- Stimulated digestion
The PNS works alongside the endocrine - Sweat glands constrict
system to return the body to its resting state - Stimulates saliva production
in the rest and digest response (involving the - Relaxes rectum
release of acetylcholine).
Think of it acting like a parachute, slowing
everything back down to normal.
The function of adrenaline: To prepare the body for defending or attacking (fight), or
running away to safety (flight), in response to a perceived threatening of stressful situation.
Physiological effects of adrenaline:
Physiological change Reason
Increased heart rate Greater blood flow to skeletal muscles
Constricts blood vessels, increasing rate of Increase blood supply/oxygen to skeletal
blood flow to the brain and skeletal muscles for physical action and to the
muscles and raising blood pressure brain for rapid response planning
Increased respiration (bronchial tubes in Greater oxygen intake
lungs dilate)
Increased sweating To regulate body temperature
Increased pupil size To let in more light for better vision
