Biopsychology
As a tutor the most common topic my tutees ask for help with in A level psychology is biopsychology. Many students find the topic challenging and the scientific terminology difficult, especially if they are not studying science alongside Psychology. However, my philosophy is keep it simple. I’ve chosen to just write about the fight or flight response, this includes elements of other areas within biopsychology too, the nervous system and the endocrine system. It is also an area which is easy to relate to, as we have all experienced the fight or flight response, especially when faced with examinations!
The Fight or Flight Response
When a person experiences a threatening or stressful situation, their body reacts in specific ways. Their heart beats faster, their breathing becomes more rapid and their muscles tense. These reactions are collectively known as the fight or flight response. This response evolved as a survival mechanism, enabling animals and humans to react quickly to life-threatening situations. The bodily changes associated with fight or flight allow an individual to fight off the threat or flee to safety. Unfortunately, the fight-or-flight response is also activated in conditions that are not life threatening, and where fighting or running is not particularly helpful.
When someone is faced with a threat, an area of the brain called the amygdala is mobilised. The amygdala associates sensory signals (what we see, hear or smell) with emotions associated with fight or flight, such as fear and anger. The amygdala then sends a distress signal to the hypothalamus, which functions like a command centre in the brain, communicating with the rest of the body through the sympathetic nervous system. The body’s response to stressors involves two major systems, one for acute (i.e. sudden) stressors such as an attack, and the second for chronic (i.e. ongoing) stressors such as a stressful job.
Acute Stress
When the amygdala senses a threat, it sends a message to the hypothalamus which communicates with the sympathetic nervous system (SNS). This activates the sympathomedullary pathway (SAM).
SAM activates the sympathetic nervous system and the adrenal medulla. This leads to the secretion of adrenaline and noradrenaline into the bloodstream. These hormones cause many of the physiological changes which are seen in the fight or flight response.
Main effects on the body
Fight or Flight
Once the threat has passed the parasympathetic nervous system (PNS) returns the body to a state of homeostasis. The parasympathetic nervous system is also known as the rest and digest system.
Stress and Illness
Our bodies are only designed for short bursts of acute stress. The sympathetic and parasympathetic work together to achieve homeostasis within the body. It is not difficult to see the serious effects that long term stress could have on the body. Having too high a heart rate and blood pressure can cause cardiovascular disorders and shutting down digestion can cause stomach issues like ulcers. Prolonged stress can also impair the immune system making people more prone to virus and infection.
Chronic Stress
If the brain continues to perceive something as threatening a second system kicks in. As the initial surge of adrenaline subsides, the hypothalamus activates a stress response system called the HPA axis. This consists of the hypothalamus, pituitary and adrenal glands.
“H” – The hypothalamus
The HPA axis relies on a series of hormonal signals to keep the SNS working. In response to a continued threat, the hypothalamus releases a chemical messenger, corticotrophin-releasing hormone (CRH), which is released into the bloodstream in response to the stressor.
“P” – The Pituitary Gland
On arrival at the pituitary gland, CRH causes the pituitary to produce and release adrenocorticotrophic hormone (ACTH). From the pituitary, ACTH is transported in the bloodstream to its target site in the adrenal glands.
“A” – The Adrenal Glands
ACTH stimulates the adrenal cortex to release various stress-related hormones, including cortisol. Cortisol is responsible for several effects in the body that are important in the fight or flight response. Some of these are positive (e.g. a quick burst of energy and lower sensitivity to pain) whereas others are negative (e.g. impaired cognitive performance and a lowered immune system).
The system is also very efficient at regulating itself. Both the hypothalamus and pituitary gland have special receptors that monitor circulating cortisol levels. If these rise above normal, they initiate a reduction in CRH and ACTH levels, thus bringing cortisol levels back to normal.
However, ongoing stress can lead to elevated levels of cortisol and this, along with other physiological changes, can lead to stress related illnesses.
Kiecolt-Glaser et al. (1984) investigated whether the stress of important examinations had an effect on the functioning of the immune system1. She took a blood sample from 75 American students 1 month before an important exam (low stress) and during the exam (high stress). The NK cell (Natural Killer cells) activity was measured. She found the NK cell activity was lower in the second sample (high stress), suggesting their immune system was weakened.
Yusuf et al. (2004) carried out a study of patients who had suffered heart attacks (myocardial infarction) in 52 countries, with a sample of 15152 cases and 14820 controls2. They found that, although lifestyle factors such as smoking were influential, stress including workplace stressors and life events had a significant impact on the rate of heart attacks. This impact was greater than obesity.
If you have found this useful and would like more help with biopsychology, contact me via Justin Craig.
Deb Gajic – Psychology tutor CPsychol, AFBPsS
References:
- Kiecolt-Glaser, J. K., Garner, W., Speicher, C., Penn, G. M., Holliday, J., & Glaser, R. (1984). Psychosocial modifiers of immunocompetence in medical students. Psychosomatic medicine, 46(1), 7-14.
- Yusuf, S., Hawken, S., Ôunpuu, S., Dans, T., Avezum, A., Lanas, F., … & Lisheng, L. (2004). Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. The lancet, 364(9438), 937-952.
Useful websites:
Psychboost: – https://www.youtube.com/channel/UCqqIPOTshm8EM8CCWkCy9Pg
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