Body's Response to Stressors

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Acute Stress: The Sympathomedullary Pathway

Acute Stress:

stress that is immediate and will not last for long.

Acute Stress causes:

  • The fight or flight response in humans

This activates:

  • The Sympathomedullary Pathway

 The stress is initially perceived by the Hypothalamus which is a small part of the brain.

This then causes the Autonomic Nervous system (ANS) to kick in.

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Autonomic Nervous System (ANS)

The ANS is part of the nervous system that controls involuntary actions.

Such as:

  • The beating of the heart
  • The widening and narrowing of blood vessels.


The ANS can be divided into two sections:

The Sympathetic Nervous System (SNS)


The Parasympathetic Nervous System (PNS)



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The ANS sections: Sympathetic Nervous System (SNS)

The Sympathetic Nervous System (SNS)

  • Arouses the body for fight or flight.

It does this by:

1. Releasing a neurotransmitter called Noradreline

This causes the following things to happen:

-The heart beats faster    -More blood created    -Pupils dilate    

-Blood is puped faster around the body     -More glucose created

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The ANS sections: SNS (continued)

(It does this by:)

2. It activates the Sympathetic Adrenal Medullary system (SAM)

The adrenal glands are found on top of the kidneys.

Adrenaline is released by the Adrenal Medulla which is inside the adrenal gland.

This causes the following things to happen:

-More oxygen produced    -More glucose produced

-Digestive system is suppressed

The SNS and the SAM system both make up the Sympathomedullary Pathway

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The ANS sections: Parasympathetic Nervous System (

The Parasympathetic Nervous System (PNS)

When the threat is perceived to be over, the PNS switches off the fight or flight response.

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