Although the sympathetic nervous system and the parasympathetic nervous system are both parts of the autonomic nervous system and have plenty of effects on the body, the two almost opposites; the former creates a certain imbalance that the latter tries to counterbalance after the stressful incident has passed.

The sympathetic nervous system controls the response humans make towards a threat: fight or flight. It is located along the lumbar regions of the spinal cord, and because the neurons are very short, the reaction is usually fast. According to Harvard Health, the ‘fight or flight’ response developed from the survival instinct; as a reaction to life-threatening situations. The body reacts to the danger involuntary; either by fighting or escaping. This, of course, creates effects on the body such as an increase in heart rate, releasing adrenaline and tensing up of the body as it becomes more alert.

The SNS, through flight of fight response, has a direct effect on the heart rate. Carol Mackersie and Natalie Calderon-Moultrie studied the SNS in relation to the heart rate. In their research (Mackersie & Calderon-Moultrie, 2016), they survey the heart rate variability (HRV) in a stressful situation, this one being giving speeches. The HRV is the “natural fluctuation in interbeat intervals that occurs over time.” (p.120). During a stressful event, the HRV appears to be way higher than usual. It is unstable and unpredictable, unlike during rest.

Add to that, and referring to the Hormone Health Network, when in a stressful situation, the body releases more adrenaline into the blood. The adrenaline triggers the fight or flight response in order to make the body act; either remove the self away to safety or attack back (2018). Other responses include the shutdown of any other function that is not related to survival, decrease in urinary output and dilation of pupils.

A study done on young adolescents (Benito-Gomez, Fletcher & Buehler, 2019), proved that when put in stressful situations, these adolescents tensed up and developed skin and respiratory problems. They had to participate in stress-inducing public speaking tasks and were surveyed throughout a certain period of time. Moreover, their social environment was also an added factor to the stress and the overall assessment of the study. The participants became more alert and their bodies tensed up.

On the contrary, and unlike the SNS, the parasympathetic nervous system controls the body when it is at rest. It is located in the sacral region of the spinal cord. The neuron pathways are much longer than the SNS’s because it is a much slower system. Frank R. Noyes and Sue D. Barber-Westin (2017), in their book, indicate that the PNS is responsible for the resting and digestion phases of the body. It unwinds the body; “undoes the work of sympathetic division after a stressful situation.” (Noyes & Barber-Westin, 2017). It restores the body to a state of calmness; decreases the heart rate and relaxes the muscles.

The PNS decreases the heart rate after it had been increased. The HRV returns back to normal in order to stabilize the whole body (Mackersie & Calderon-Moultrie, 2016). The heart is now stable and beating as normally as it should be because the cause of the stress is gone. Moreover, the muscles begin to relax. This helps in digestion and increase in urinary output. Kristeen Browning and Alberto Travagli’s research published on the National Center for Biotechnology Information website indicates that the PNS exerts excitatory control over the digestive system (Browning, K. N., & Travagli, R. A., 2014). This is studied through the observation of the gastrointestinal tract.

So now that we have identified the effects  of a stressful situation and the modifications it does to the body, treatment becomes a must. The SNS reacts to remove the body from danger and the PNS tries to balance the body again after it’s been disrupted. This constant push and pull will lead to an exertion and burnouts. The aforementioned effects of both SNS and PNS take a toll on the body. Therefore, what can be done is to constantly be mindful of our bodies and its needs. First, meditating regularly will lessen stress. This helps in avoiding the need for the SNS to act in the first place. Second, having a healthy lifestyle aids in preventing lasting damage after the PNS acts. If we can’t avoid the fire, we can try our best to make sure that the aftermath isn’t as permanent. A healthy lifestyle will make sure the body bounces back safely and quickly with the least collateral damage possible. Lastly, psychotherapy and specified programs are sure to guide you throughout your process to regain balance.

Thus, if we got lost in the maze due to a stressful incident, our bodies will have a severe reaction through the SNS. If the situation extends and the reason for this misery continues, the body will drain out fast —we will be forever lost in the maze and imprisoned inside. The PNS will try its best to restore the body into its ideal shape. However, the constant existence of the main instigator will inhibit any attempt at healing. This will lead to many complications in the body, a burnout and —if no action is done to help— the body will shut down completely.

The BALANCE rehab center believes that there are plenty of ways to avoid burnout and permanent damages to your body. We aim to take your hand and guide you through this maze that is both incredibly well-structured, but fragile at the same time. If your PNS does not counterbalance your SNS, a critical imbalance will take place. Thus, we aim —through our psychotherapy and stress management— to work on the symptoms and reach towards the roots of the problem so we can walk harmlessly together. Taking care of yourself should always be your first priority. So take the decision to sort your life and reach out.


Benito-Gomez, M., Fletcher, A. C., & Buehler, C. (2019). Sympathetic and parasympathetic nervous system functioning and experiences of peer exclusion: links to internalizing problems in early adolescence. Journal of Abnormal Child Psychology, 47(4), 633-644.

Browning, K. N., & Travagli, R. A. (2014). Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions. Comprehensive Physiology4(4), 1339–1368.

Hormone Health Network. “Adrenaline | Hormone Health Network.” (2018)., Endocrine Society, 4 November 2020,

Mackersie, C. L. & Calderon-Moultrie, N. (2016).  Autonomic Nervous System Reactivity During Speech Repetition Tasks: Heart Rate Variability and Skin Conductance. Ear and Hearing: July/August 2016 – Volume 37 – Issue – p 118S-125S

McCorry, L. K. (2007). Physiology of the autonomic nervous system. American journal of pharmaceutical education, 71(4), 78.

Noyes., F., 2017. Noyes’ Knee Disorders: Surgery, Rehabilitation, Clinical Outcomes (Second Edition). 2nd ed. Elsevier, pp.1122-1160.

Publishing, H., 2020. Understanding The Stress Response – Harvard Health. [online] Harvard Health. Available at: <> [Accessed 3 November 2020].