The fight or flight response | AQA A-Level Psychology Revision
- Revision Notes
- Aug 3
- 14 min read
Updated: 6 days ago
For 7182 specification, first teach in September 2025
AQA A-Level Psychology | Free Revision Notes
Estimated study time: 40 minutes
These Fight or flight response A-Level Psychology revision notes explain how the body responds rapidly to a perceived threat. You will examine how the autonomic nervous system activates an endocrine response, how adrenaline changes bodily activity and how the nervous and endocrine systems work together during stressful situations. This lesson applies knowledge from automatic regulation by the autonomic nervous system and communication through glands and hormones.
Learning Objectives 🎯
By the end of this revision page, you should be able to:
Define the fight or flight response.
Explain how a perceived threat activates the response.
Explain the role of the autonomic nervous system.
Explain the role of adrenaline.
Describe bodily changes associated with fight or flight.
Apply nervous and endocrine communication to stressful situations.
Revision Notes 📚
Fight or flight response A-Level Psychology revision overview
The fight or flight response is an automatic biological response to a perceived threat.
It prepares the body to:
Confront the threat, which is the fight response.
Escape from the threat, which is the flight response.
The response involves cooperation between:
The nervous system.
The autonomic nervous system.
The endocrine system.
The adrenal glands.
The hormone adrenaline.
The overall sequence is:
Threat detected → nervous-system activation → adrenal glands release adrenaline → bodily activity changes → individual is prepared for action
Why does the fight or flight response occur?
A threat may require an immediate response.
The body must rapidly redirect resources towards the systems most useful for dealing with danger.
This may involve preparing the person to:
Move quickly.
Respond to sensory information.
Deliver more oxygen and energy to active muscles.
Remain alert.
Delay less urgent bodily activity.
The fight or flight response is therefore a coordinated preparation for action rather than a single behaviour.
A person may experience the biological response without actually fighting or running away.
Fight and flight
The two possible responses describe different actions.
Response | Meaning |
Fight | Confronting or dealing directly with the threat |
Flight | Escaping from or avoiding the threat |
For example:
Moving towards somebody to protect another person could represent fight.
Running away from an immediate danger could represent flight.
The biological preparation may be similar in both cases because each response requires energy and rapid physical activity.
The role of the nervous system
The nervous system detects and processes information about possible threats.
The process begins when sensory receptors detect information from the environment.
For example:
A person hears a sudden threatening sound.
Sensory information travels towards the central nervous system.
The information is processed.
The autonomic nervous system is activated.
Internal bodily activity begins to change.
Sensory and neural communication can be reviewed through incoming, connecting and outgoing neural pathways.
The autonomic nervous system
The autonomic nervous system is the division of the peripheral nervous system involved in the automatic regulation of internal bodily processes.
It operates without requiring a person to make a deliberate conscious decision.
During a threatening situation, the person does not consciously decide to:
Increase their heart rate.
Alter their breathing.
Redirect bodily resources.
Release a hormone.
These changes occur automatically.
The fight or flight response therefore illustrates the role of the autonomic nervous system described in somatic and autonomic communication.
The sympathetic nervous system
The autonomic nervous system can produce increased bodily arousal when a threat is detected.
This activating part of the autonomic response is associated with the sympathetic nervous system.
Its general function during fight or flight is to prepare the body for rapid action.
The sympathetic response leads to:
Increased physiological arousal.
Activation of the adrenal glands.
Release of adrenaline.
Changes that support fight or flight behaviour.
The individual does not need to consciously initiate these changes.
The endocrine response
The fight or flight response also involves the endocrine system.
The endocrine sequence is:
A threatening situation is detected.
Nervous-system activity activates the adrenal glands.
The adrenal glands release adrenaline.
Adrenaline enters the bloodstream.
It travels to target organs.
Target organs change their activity.
This demonstrates how neural and hormonal communication can form one coordinated response.
The adrenal glands
The adrenal glands are glands within the endocrine system.
During the fight or flight response, they release the hormone adrenaline.
The adrenal glands are biological structures, while adrenaline is the chemical messenger they release.
Adrenal glands | Adrenaline |
Endocrine glands | A hormone |
Produce and release the chemical message | Carries the chemical message |
Remain in a fixed location | Travels through the bloodstream |
Are activated during the response | Affects target organs |
A gland is not the same as a hormone. The gland releases the hormone.
What is adrenaline?
Adrenaline is a hormone released by the adrenal glands during the fight or flight response.
It is carried through the bloodstream and affects target organs.
Its overall role is to increase physiological arousal and prepare the body for rapid action.
The pathway can be represented as:
Adrenal glands → adrenaline → bloodstream → target organs → bodily changes
Adrenaline is part of endocrine communication because it:
Is released by a gland.
Travels through the bloodstream.
Acts on target cells with suitable receptors.
Alters bodily functioning.
The effects of adrenaline
Adrenaline produces changes that help prepare the body to fight or escape.
These may include:
An increase in heart rate.
An increase in breathing rate.
Greater availability of energy.
Increased blood flow towards muscles needed for movement.
Reduced activity in systems not immediately needed for survival.
Increased physical alertness and readiness.
These changes support rapid action.
For example, increased heart and breathing rates help deliver oxygen to muscles that may be needed for running or fighting.
Increased heart rate
During fight or flight, adrenaline contributes to an increase in heart rate.
A faster heart rate helps blood circulate more rapidly.
This supports the delivery of:
Oxygen.
Energy resources.
Other substances needed by active tissues.
The change is involuntary and forms part of the autonomic response.
Increased breathing rate
Breathing rate may increase during the fight or flight response.
This allows more oxygen to enter the body.
The oxygen can be transported to tissues that need it for increased physical activity.
The person does not need to decide consciously to breathe more quickly.
Increased availability of energy
Fight or flight may require rapid muscular activity.
Adrenaline therefore helps make energy more readily available for immediate use.
This supports actions such as:
Running.
Moving quickly.
Lifting.
Defending oneself.
Responding rapidly to danger.
The response prioritises immediate biological demands over less urgent activities.
Redirecting bodily resources
During a threat, resources are redirected towards processes that support immediate survival.
More resources may be directed towards:
Skeletal muscles.
Heart and breathing activity.
Rapid sensory and motor responses.
Activity associated with less immediately important functions, such as digestion, may be reduced temporarily.
This does not mean that these functions stop permanently. Their activity is adjusted while the threat is present.
A coordinated response
Fight or flight is not produced by adrenaline alone.
It involves several connected processes:
Sensory information about a threat is detected.
Information travels through the nervous system.
The central nervous system processes the information.
The autonomic nervous system produces automatic changes.
The adrenal glands are activated.
Adrenaline is released into the bloodstream.
Target organs respond.
The body becomes prepared for action.
This shows why the response is described as coordinated.
Nervous and endocrine communication working together
The nervous and endocrine systems make different contributions.
Nervous-system contribution | Endocrine-system contribution |
Detects and transmits information about the threat | Releases hormones |
Carries rapid signals along neurons | Carries adrenaline through the bloodstream |
Activates an immediate response | Supports wider bodily changes |
Communicates through neurons and synapses | Communicates through glands, hormones and target organs |
Includes autonomic regulation | Includes activation of the adrenal glands |
The nervous system initiates rapid communication, while endocrine activity helps produce and maintain physiological changes.
Speed and duration
Nervous and endocrine communication differ in their timing.
Nervous communication
Signals travel rapidly along neurons.
Communication is directed along specific pathways.
The response can begin very quickly.
Endocrine communication
Hormones travel through the bloodstream.
Their effects usually take longer to begin.
Their effects may last longer.
During fight or flight, this combination allows the body to respond rapidly while also maintaining the biological changes required to manage the threat.
The general differences are covered in glands, hormones and nervous communication.
Neural communication during fight or flight
Information travels through neural pathways during the response.
For example:
A sensory neuron carries information about a possible threat towards the central nervous system.
Relay neurons pass information within the central nervous system.
Motor neurons may carry instructions to skeletal muscles.
Autonomic communication changes internal bodily activity.
Neurons communicate with one another across synapses.
At each synapse:
Neurotransmitters are released.
They cross the synaptic gap.
They bind to receptor sites.
They excite or inhibit the next neuron.
This process is reviewed in neurotransmitters, excitation and inhibition.
Returning the body to its resting state
Once the threat has passed, the body no longer needs to remain in a highly aroused condition.
The calming part of the autonomic nervous system is associated with the parasympathetic nervous system.
Its role is to reduce the arousal produced during fight or flight and return bodily activity towards its resting state.
This may involve:
Reducing heart rate.
Reducing breathing rate.
Restoring digestive activity.
Reducing the immediate mobilisation of energy.
The two parts of the autonomic nervous system therefore have contrasting roles.
Sympathetic activity | Parasympathetic activity |
Increases physiological arousal | Reduces physiological arousal |
Prepares the body for fight or flight | Returns the body towards its resting state |
Activates the response to a threat | Helps restore normal bodily functioning |
Supports immediate action | Supports recovery after the threat |
Fight or flight in modern stressful situations
The fight or flight response can occur when a person perceives a threat even if immediate physical action is not required.
Possible situations include:
Giving a presentation.
Entering an examination.
Attending an interview.
Receiving unexpected bad news.
Experiencing conflict.
Hearing a sudden alarm.
For example, a student waiting outside an examination room may experience:
A faster heart rate.
Quicker breathing.
Increased alertness.
Reduced digestive activity.
A feeling of physical tension.
These changes can be explained through autonomic nervous-system activation and the release of adrenaline.
Perceived and actual threats
A threat does not need to cause physical injury for the response to occur.
What matters is that the situation is processed as threatening or demanding.
For example:
Two students are asked to speak in front of their class. One interprets the task as an exciting opportunity, while the other perceives it as highly threatening.
The second student may show a stronger fight or flight response because the situation is experienced as a greater threat.
The biological response is connected with the person’s interpretation of the situation, even though the physiological changes themselves are automatic.
Applying the response to a physical threat
Consider this scenario:
Imogen hears a vehicle approaching rapidly while she is crossing a road. She runs to the pavement. Her heart is beating quickly and her breathing rate has increased.
The response can be explained as follows:
Sensory receptors detect information about the approaching vehicle.
Sensory neurons transmit information towards the central nervous system.
The threat activates the autonomic nervous system.
The sympathetic response increases physiological arousal.
The adrenal glands release adrenaline.
Adrenaline travels through the bloodstream to target organs.
Heart and breathing rates increase.
Motor neurons carry instructions to skeletal muscles.
Imogen is prepared to escape from the threat.
Her movement towards the pavement is an example of flight.
Applying the response to a psychological stressor
Consider another scenario:
Before delivering an important speech, Nathan notices that his heart is beating quickly and his breathing has become faster.
The response can be explained through the interaction of the nervous and endocrine systems:
Nathan perceives the speech as threatening or demanding.
The autonomic nervous system is activated.
Sympathetic activity increases bodily arousal.
The adrenal glands release adrenaline.
Adrenaline travels through the bloodstream.
It affects target organs, increasing heart and breathing activity.
Nathan’s body becomes prepared for action even though he does not need to run away or fight.
A method for answering application questions
Use the following structure.
1. Identify the stressful situation
State what the person perceives as threatening.
2. Identify nervous-system activity
Explain that the threat activates the autonomic nervous system.
3. Identify the gland
State that the adrenal glands are activated.
4. Identify the hormone
State that adrenaline is released into the bloodstream.
5. Identify target effects
Use bodily changes described in the scenario, such as increased heart or breathing rate.
6. Link the changes to survival
Explain how the changes prepare the person to fight or escape.
For example:
The approaching dog is perceived as a threat, activating Arlo’s autonomic nervous system. His adrenal glands release adrenaline into the bloodstream. Adrenaline increases his heart and breathing rates, helping deliver oxygen and energy to his muscles. This prepares Arlo to escape from the dog.
Separating observation from explanation
In application questions, distinguish the observed response from the biological explanation.
Observation from a scenario | Biological explanation |
The person’s heart beats faster | Adrenaline increases physiological arousal |
The person begins breathing quickly | The body is increasing oxygen availability |
The person runs away | Motor output produces a flight response |
The person’s body later calms | Parasympathetic activity returns the body towards rest |
A strong answer connects each observed detail to the relevant biological process.
Fight or flight is automatic
The response is automatic because its physiological features are not initiated through deliberate conscious choice.
A person may control some later behaviour, such as choosing whether to leave a situation, but they do not consciously control every internal change involved in the initial response.
For example:
Deciding to leave an examination hall would be a conscious behaviour.
The sudden increase in heart rate would be an automatic bodily response.
This distinction helps separate voluntary behaviour from autonomic activity.
Fight or flight is not the same as feeling afraid
Fear may accompany the fight or flight response, but the terms are not identical.
Fear refers to an emotional experience.
Fight or flight refers to a coordinated biological response preparing the body for action.
A person may display physiological arousal even when they describe their emotional state differently.
An examination answer should therefore focus on biological mechanisms rather than stating only that the person feels scared.
The response does not guarantee fighting or fleeing
Biological preparation does not determine the person’s final action completely.
A person experiencing the response may:
Fight.
Run away.
Remain still.
Seek help.
Continue with the situation.
Use a coping strategy.
The term fight or flight describes the body’s preparation for rapid action, not the only two behaviours a person can ever perform.
Fight or flight and prolonged stress
The fight or flight response is useful for managing an immediate threat.
However, stressful situations may sometimes continue rather than ending quickly.
The course later distinguishes this rapid response from other biological pathways involved in stress.
The immediate nervous and adrenal response is developed further in the rapid response to a stressor, while a different hormonal process is considered in the response to continuing stress.
Writing an effective explanation
A strong explanation might state:
The fight or flight response is an automatic biological response to a perceived threat. The autonomic nervous system activates the adrenal glands, which release adrenaline into the bloodstream. Adrenaline acts on target organs and increases physiological arousal, including heart and breathing activity. These changes increase the availability of oxygen and energy, preparing the person to confront or escape the threat. Once the danger has passed, parasympathetic activity returns the body towards its resting state.
This answer:
Defines the response.
Explains nervous-system involvement.
Identifies the adrenal glands.
Explains the role of adrenaline.
Links physiological changes to action.
Explains recovery after the threat.
Key Words 🔑
Key word | Student-friendly definition | How it may be used in an exam |
Fight or flight response | An automatic biological response that prepares the body to confront or escape a perceived threat. | Define and explain the response to a stressor. |
Threat | A situation processed as presenting possible danger or harm. | Identify what activates the response in a scenario. |
Stressor | An event or situation that places demands on an individual and may produce a stress response. | Apply biological systems to stressful situations. |
Autonomic nervous system | The division of the PNS that regulates involuntary internal bodily processes. | Explain why the response occurs automatically. |
Sympathetic nervous system | The activating part of the autonomic nervous system that increases arousal during fight or flight. | Explain the preparation for immediate action. |
Parasympathetic nervous system | The part of the autonomic nervous system that returns the body towards its resting state. | Explain recovery after a threat. |
Endocrine system | A system of glands that release hormones into the bloodstream. | Explain hormonal communication during fight or flight. |
Adrenal glands | Endocrine glands that release adrenaline during fight or flight. | Identify the source of adrenaline. |
Adrenaline | A hormone that increases physiological arousal and prepares the body for action. | Explain bodily changes during a threat. |
Hormone | A chemical messenger released by a gland and carried in the bloodstream. | Explain how adrenaline reaches target organs. |
Target organ | An organ containing cells that respond to a particular hormone. | Explain where adrenaline produces its effects. |
Physiological arousal | Increased bodily activity that prepares the person to respond. | Describe the effect of sympathetic activity and adrenaline. |
Sensory neuron | A neuron carrying information from receptors towards the CNS. | Explain how information about a threat is transmitted. |
Motor neuron | A neuron carrying instructions from the CNS towards an effector. | Explain how physical action may be produced. |
Homeostasis | The maintenance of a stable internal state. | Explain the return towards normal bodily functioning after a threat. |
Common Mistakes ⚠️
Mistake: Describing fight or flight as a conscious decision.
Why this is incorrect:Its physiological changes are produced automatically through the autonomic nervous and endocrine systems.
How to improve:Distinguish automatic bodily preparation from the person’s later behavioural choices.
Mistake: Saying that adrenaline is a gland.
Why this is incorrect:Adrenaline is a hormone released by the adrenal glands.
How to improve:Use the sequence: adrenal gland releases adrenaline.
Mistake: Saying that adrenaline travels along neurons.
Why this is incorrect:Adrenaline travels through the bloodstream as part of endocrine communication.
How to improve:Separate hormonal transmission through blood from neural transmission along neurons.
Mistake: Explaining the response using only the nervous system.
Why this is incorrect:Fight or flight involves cooperation between nervous and endocrine communication.
How to improve:Include autonomic activation, the adrenal glands and adrenaline.
Mistake: Explaining the response using only adrenaline.
Why this is incorrect:Adrenaline is one part of a coordinated response initiated through nervous-system activity.
How to improve:Begin with threat detection and autonomic activation before explaining hormonal release.
Mistake: Saying that parasympathetic activity begins the fight or flight response.
Why this is incorrect:Sympathetic activity prepares the body for action. Parasympathetic activity returns it towards rest.
How to improve:Remember: sympathetic activates, parasympathetic calms.
Mistake: Listing bodily changes without explaining their purpose.
Why this is incorrect:The question may require an explanation of how the changes support fight or flight.
How to improve:Link increased heart or breathing rate to the delivery of oxygen and energy to muscles.
Mistake: Saying the response occurs only during physical danger.
Why this is incorrect:Psychological situations may also be perceived as threatening and activate the response.
How to improve:Apply the response to stressors such as examinations, interviews or public speaking where appropriate.
Mistake: Assuming that the person must fight or run away.
Why this is incorrect:The body is prepared for rapid action, but the person may perform another behaviour.
How to improve:Describe fight and flight as possible responses rather than guaranteed actions.
Mistake: Describing faster heart rate as a voluntary motor response.
Why this is incorrect:Heart-rate changes are regulated automatically by the autonomic nervous system.
How to improve:Distinguish internal autonomic changes from voluntary movement controlled through the somatic system.
Mistake: Naming the biological systems without applying details from the scenario.
Why this is incorrect:Application marks require a direct connection with the person’s stressor and bodily response.
How to improve:Identify the threat, relevant physiological changes and how they prepare the named person for action.
Exam-Style Questions ✍️
Question 1
Which one of the following releases adrenaline during the fight or flight response?
A. The motor neurons
B. The adrenal glands
C. The spinal cord
D. The sensory receptors
[1 mark]
Question 2
Define the fight or flight response.
[2 marks]
Question 3
Explain the role of adrenaline in the fight or flight response.
[4 marks]
Question 4
Explain one difference between sympathetic and parasympathetic activity.
[4 marks]
Question 5
Describe how the nervous and endocrine systems work together during the fight or flight response.
[6 marks]
Question 6
Before a job interview, Max notices that his heart is beating quickly and his breathing rate has increased.
Using your knowledge of the fight or flight response, explain Max’s physiological reaction.
[4 marks]
Question 7
Leonie sees a large dog running towards her. She turns and runs in the opposite direction.
Explain how sensory neurons, the autonomic nervous system, the adrenal glands and motor neurons contribute to Leonie’s response.
[6 marks]
Question 8
A student says:
Adrenaline is a neurotransmitter that crosses a synapse and causes the fight or flight response.
Explain why this statement is incorrect.
[4 marks]
Question 9
Explain how the body returns towards its resting state after a perceived threat has passed.
[4 marks]
Question 10
A cyclist suddenly sees a car pull into the road ahead. The cyclist’s heart and breathing rates increase, and they quickly turn the handlebars to avoid the car.
Using your knowledge of the nervous and endocrine systems, explain the cyclist’s response.
[8 marks]
Comments