How trauma affects sympathetic and parasympathetic nervous system

The human body is an intricate system. One that is constantly responding to the environment and internal stimuli. At the core of these responses are two critical systems: the sympathetic and parasympathetic nervous systems. These two systems work together to regulate our body's functions, maintaining a delicate balance that allows us to adapt to different situations and maintain overall well-being.

The sympathetic nervous system is often referred to as the "fight or flight" response. When we perceive a threat or are under stress, this system kicks into action. It rapidly prepares the body for action by increasing heart rate, dilating the airways to help us breathe more easily, and releasing adrenaline to boost energy levels. This heightened state of arousal is essential for dealing with immediate challenges, whether it's escaping from danger or confronting a stressful situation.

The parasympathetic nervous system is conversely known as the "rest and digest" response. This system is responsible for promoting relaxation, conserving energy, and supporting processes such as digestion and tissue repair. When the parasympathetic nervous system is active, heart rate decreases, breathing slows down, and blood flow is directed towards the digestive organs, allowing the body to rest and recover.

Two systems that work in tandem

Continuously balancing each other to keep our bodily functions in check. When one is activated, the other is suppressed, ensuring that our body can adapt to different circumstances while maintaining overall stability.

Chronic activation of the sympathetic nervous system

Seen in prolonged periods of stress or from trauma, can have detrimental effects on health, leading to issues such as high blood pressure, weakened immunity, and digestive problems. 

A well-functioning parasympathetic system 

Is essential for promoting recovery, supporting healthy digestion, and maintaining a calm, balanced state. Recognising the roles of these two systems, individuals can learn to manage stress more effectively and promote relaxation and well-being. 

Trauma and the brain

The prefrontal cortex and limbic centre are two crucial areas of the brain that play a significant role in our response to trauma. The prefrontal cortex is responsible for our higher cognitive functions such as decision making, problem-solving, and emotional regulation. 

When we experience trauma, this part of the brain can become overwhelmed, making it difficult for us to think clearly and make rational decisions. On the other hand, the limbic centre, which includes the amygdala and hippocampus, is responsible for our emotional responses and memory formation. During a traumatic event, the limbic centre is highly activated, causing us to feel intense emotions and creating vivid memories of the event. 

Understanding the role of these brain regions in trauma can help us better understand and manage our reactions to traumatic experiences.

Fight flight freeze fawn

The area of the brain that deals with rational chronological thoughts is the pre-frontal cortex and the amygdala supports emotional valence for your experience eg it monitors positive or negative effects. The amygdala makes a note for survival purposes if you are highly upset.

The amygdala also triggers the fight, flight, freeze or face response. The logical prefrontal cortex can switch off the fight or flight response. During overwhelming experience or trauma, the amygdala activates the adrenal gland and signals the hyperthermus to activate the pituitary and adrenal system to fight or run. 

This process shuts down other systems, to save energy. This is why during traumatic events your memory and other abilities including speech and language can be affected along with the ability to organise recall of an experience.

You may experience a range of symptoms that can appear at the time or even much later. In some people there may be no effect or reactions at all. These symptoms are normal survival responses. Trauma symptoms will vary between individuals. 

Unconscious effects

The two systems in the brain work differently from each other. The one for emotions like fear and anxiety, we are aware of. The other for the fight-flight freeze response is unconscious and it does not connect to our language centres. This system can sense a threat without our awareness and may be linked to centres deep in the brain. When activated the adrenal glands create adrenaline and cortisol and trigger the fight or flight response, increasing heart rate and diverting resources to run freeze or fight. 

Memories related to fight or flight situations are kept, to inform us of future threats. This influences our ability to think, plan reason or use logic to problem solve. We also cannot create memory on a timeline as easily, so it becomes fragmented. This leads to an embodied awareness of threat with no rational or logical memory and the feeling of unease when sensing a similar situation to one in the past.