Biopsychology: The fight or flight response

Question 1

How does stress link to the flight or fight response?

Answer 1

Humans and animals have developed mechanisms to deal effectively with potential threats / stressors in their environments. The response that prepares us to either confront or run away from a threat is called the fight or flight response.

This response is generated from the autonomic nervous system, specifically the sympathetic branch. It is a reflex response designed to help an individual react quicker than normal circumstances would permit.

Question 2

what are the two types of stress response?

Answer 2

In fact, our stress response can be on of two types depending on the appraisal of that threat / stressor.

Short term stressors - our fight or flight is activated (i.e., it’s an emergency)

Long term stressors - different systems are activated (this is called the Pituitary Adrenal system)

Although we will make the distinction between the body’s response to immediate short term (acute) and long term (chronic) stressors, the first stage is the same.

Question 3

Explain the stages of appraisal of stressor

Answer 3

1. The body appraises the situation using its sensory systems and stored memories. So the hippocampus (memory area in the brain) and amygdala (emotional regulation area in the brain) try to recognise emotional reactions to stimuli and access stored memories for potential danger.
2. If the situation is appraised as potentially stressful, the hypothalamus is alerted. The hypothalamus controls the systems that have central roles in the stress response, the HPA axis and the SAM pathway. We are only concerned with the SAM system.

Question 4

The Body’s Response to ACUTE stress: SAM Pathway

Answer 4

1. A situation is perceived as stressful due to memories, emotions or instincts etc.
2. The hypothalamus (in the CNS) is alerted. This recognises the stress is acute so…
3. … the Sympathomedullary (SAM) pathway is activated (this is the sympathetic branch of the autonomic nervous system that goes directly to the adrenal medulla).
4. This stimulates the adrenal gland (specifically the adrenal medulla, i.e., the inner core) which are situated just above the kidneys.

5.The adrenal medulla secretes the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine).

6. These hormones prepare the body for fight or flight and causes the following bodily effects (among others):
   Increasing the heart rate;
   Increasing blood pressure;
   Expanding the air passages of the lungs;
   Enlarging the pupil in the eye;
   Redistributing blood to the muscles;
   Altering the body’s metabolism, so as to maximise blood glucose levels (primarily for the brain).

Question 5

Describe increase in perspiration as an effect of adrenaline

Answer 5

Sweat helps the body cool down quicker.

When sweat evaporates, it cools the body to prevent it from overheating, and thus allows us to continue fighting or fleeing from danger without becoming exhausted from heat.

Question 6

Name some effects of adrenaline

Answer 6

Increasing the heart rate;
Increasing blood pressure;
Expanding the air passages of the lungs;
Enlarging the pupil in the eye;
Redistributing blood to the muscles;
Altering the body’s metabolism, so as to maximise blood glucose levels (primarily for the brain).

Question 7

Describe increased respiration rate as an effect of adrenaline

Answer 7

This occurs in order to increase the amount of oxygen you take in since the body needs higher levels of oxygen to be able to fight or flee.

Oxygen is used by the muscles to make energy for fighting or fleeing danger.

Question 8

Describe increased blood flow to muscles as an effect of adrenaline

Answer 8

This occurs in order to efficiently circulate oxygen and nutrients to your muscles for fighting or fleeing.

This supports your body for quick action.

Question 9

Describe pupil dilation as an effect of adrenaline

Answer 9

This allows more light to enter your eyes so that you can see your surroundings better.

Your eyes do this so you can be more observant of the threat causing the reaction.

Question 10

Describe increased heart rate and blood pressure as an effect of adrenaline

Answer 10

This occurs in order to efficiently circulate blood with oxygen and nutrients to your muscles for fighting or fleeing.

It essentially enables energy to be pumped around your body quicker.

Question 11

Describe reduced activity in the digestive system as an effect of adrenaline

Answer 11

Precious energy and resources are needed elsewhere (e.g., muscles for fleeing or fighting).

Processes within the digestive system are temporarily halted to allow these resources to be used.

Question 12

Fight or flight response summary

Answer 12

So, when we experience a stressor, our body reacts by activating the autonomic nervous system, specifically the sympathetic branch.
This arouses the body and activates the SAM pathway, which has the effects outlined above and on the previous page.
However, after a few minutes the parasympathetic branch of the ANS will be activated.
This is a countershock response which reduces the fight or flight response and returned the body back to normal.
This normal state is known as homeostasis.