A heart isn't defibrillated like in the movies, or from defibrillation to rumination....

I recently saw a LinkedIn post that inspired me to write on the same topic. Maybe it doesn't directly relate to human resources management, but still… I was particularly struck by Dr. Jane's image, the very one I've used here.

Essentially, we don't think much about the heart, even though we feel it every second. The fact that we don't give much thought to our heart, which we can feel and 'hear', made me wonder about other organs that we neither see, hear, nor feel. Naturally, the brain, being a marvel, was my first association for 'invisibility'.

A normal heart rhythm consists of three parts: the P wave, the QRS complex, and the T wave. The P wave is an electrical impulse sent from the atria (upper chambers of the heart) to the ventricles (lower chambers of the heart). The QRS complex is an electrical impulse sent from the ventricles to the heart's vessels. The T wave is the recovery period after the ventricles contract. Depending on the individual, a normal heart rhythm ranges between 60 and 100 beats per minute. Deviations from this range are generally considered abnormal.

All of this could also be described something like this: The cardiac cycle refers to the sequence of events that occur in the heart during one complete heartbeat. The cardiac cycle includes the contraction (systole) and relaxation (diastole) of the atria and ventricles, as well as the opening and closing of the heart valves. We can divide it into four phases:

• The first phase is atrial systole, during which the atria contract and push blood into the ventricles.
• The second phase is ventricular diastole, during which the ventricles relax and fill with blood.
• The third phase is ventricular systole, during which the ventricles contract and pump blood from the heart to the lungs for gas exchange (oxygen and carbon dioxide), and then the blood goes to the rest of the body.
• The final phase is atrial diastole, during which the atria relax and fill with blood returning to the heart from the body.

Regarding gas exchange, there's an interesting test that was very relevant during C-19 (and generally for lung patients): arterial blood gas analysis. It's usually taken from the radial artery on the inner side of the forearm, near the wrist. That's the famous jugular vein we used to look for as kids. Drawing blood from an artery is also interesting because you have to 'pull' the syringe and then pierce it at the end (well, maybe it's done more modernly today). Arterial blood comes out 'under pressure,' so it needs to equalize with atmospheric pressure. Otherwise, since arteries are quite deep, it's not easy to 'hit' the radial artery. If you miss, a significant hematoma will form on the wrist.

Ah, yes. From the aforementioned systole and diastole, blood pressure is derived, usually in mmHg. This is what's commonly known as 'upper and lower pressure' among people.

And before I get to the brain, defibrillation. Defibrillating or resuscitating a patient in movies is dramatic. The scenario usually goes something like this:

• Asystole!!!!! (flatline)
• Worried faces.
• Charging!!! (defibrillator whirs)
• Clear!!!!
• Thump!
• Then either the 'patient' is alive or not; the script branches here:
• Alive: Everyone rejoices
• Not alive: A distant gaze

However, a defibrillator is mainly used for cardiac arrhythmias, specifically ventricular fibrillation and ventricular tachycardia, and has nothing to do with movie scenes.

The cardiac cycle is controlled by electrical impulses originating from the sinoatrial (SA) node and the atrioventricular (AV) node. In the absence of a defibrillator, a precordial thump can be performed, roughly in the middle of the chest with a fist. This is to 'reset' the aforementioned nodes so that they don't send impulses 'for nothing.' But if movies showed that, it wouldn't be 'tense' at all.

The Brain and 'Arrhythmias'

But what happens when life gets 'tense'? What happens when we are emotionally hurt?

Our brain essentially doesn't care whether we are emotionally hurt or genuinely physically injured. When we experience emotional pain, it activates the same neural pathways in the brain as physical pain.

The amygdala is a small, almond-shaped structure located in the brain that is involved in many important functions, including emotions and decision-making. In situations perceived as life-threatening, the amygdala plays a key role in activating the body's stress response. When the amygdala detects a potential threat, it sends a signal to the hypothalamus, which, in turn, activates the sympathetic nervous system. This causes the release of stress hormones, such as adrenaline and cortisol, which help prepare the body for action.

In addition, emotional pain can also activate the default mode network (DMN).

The DMN is a large brain network consisting of the medial prefrontal cortex, the posterior cingulate cortex ('parts' of the brain), and gyri (gyri are ridges, and sulci are grooves on the brain's 'surface'). The DMN is 'known' for being active when a person is not focused on the external world, and the brain is in a wakeful state (not asleep). These are situations like when we daydream or 'wander in thought'.

Also, when we are emotionally hurt, this can lead to the activation of the body's 'fight or flight' response (which again involves an increase in stress hormone levels).

Flight or Fight

This connection between emotions and the body's physiological reactions is regulated by the hypothalamus-pituitary-adrenal (HPA) axis. The hypothalamus then determines whether the 'fight or flight' response should be activated, and the pituitary and adrenal glands produce stress hormones that are distributed throughout the body, including adrenaline and cortisol.

The 'fight or flight' mode, also known as the stress response, is a physiological response that prepares the body to react to a perceived threat. In 'fight' mode, the body releases hormones like adrenaline and noradrenaline. Adrenaline increases heart rate, blood pressure, and blood sugar levels, preparing the body for physical exertion. Noradrenaline also increases heart rate and blood pressure, and directs blood flow to the muscles and away from, at that moment, non-essential functions like digestion.

In 'flight' mode, the body releases hormones like cortisol. Cortisol increases blood sugar levels, suppresses the immune system, and increases the sensitivity of the amygdala, the brain's fear center, which can lead to feelings of anxiety. Cortisol also promotes the release of insulin and other hormones that regulate metabolism and hunger.

It is important to note that these hormones and corresponding physiological responses are not mutually exclusive and there is a degree of overlap between them. Also, the fight or flight response is a normal bodily reaction to perceived stress, but when activated too often or for too long, it can have negative effects on physical and mental health.

Some of the ways cortisol acts:

• Increased heart rate: Cortisol can cause an increase in heart rate, also known as tachycardia. This is a response to the 'fight or flight' response, which is triggered by stress.
• Elevated blood pressure: Cortisol can also cause an increase in blood pressure, which can further strain the cardiovascular system.
• Weakened immune system: Cortisol can weaken the immune system, making the body more susceptible to infections and diseases.
• Digestive problems: Cortisol can cause digestive problems such as nausea, vomiting, and diarrhea.
• Insomnia: Cortisol can also interfere with sleep, leading to insomnia.
• Increased risk of depression and anxiety: Long-term exposure to cortisol can increase the risk of developing depression and anxiety disorders.

The DMN Network

The Default Mode Network (DMN) is a network of brain regions that is active when the brain is 'at rest' and not focused on external tasks or stimuli. The DMN is believed to be involved in various functions such as self-reflection, memory, and emotion regulation.

As mentioned, we use the DMN when we daydream or, even better, at the end of the day when we reflect on it, or when we are alone with our thoughts.

According to Dr. Caroline Leaf, a clinical and cognitive neuroscientist, when we are alone with our thoughts, we 'restart' the brain and activate the DMN network, thereby improving the brain's 'health and vitality'. This network never completely shuts off, but it requires us to spend a certain amount of time each day away from technology to truly utilize our brain and think deeply, which allows for its progress.

However, studies have shown that the DMN is also activated when individuals experience emotional pain, and DMN activity increases, especially in the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC). It is believed that these areas, in addition to playing a role in reflection, are also involved in processing and connecting emotional information with memories.

Such increased activity in the DMN can also have negative consequences. Research has shown that increased DMN activity is associated with rumination, which is the repetitive and excessive focusing on negative emotions and thoughts. Rumination can prolong emotional pain and may contribute to the development of mental health disorders such as depression and anxiety. When something emotionally 'troubles' us, thanks to the activation of the DMN network, we try to think about it, hoping that reflection will solve the problem. However, often the opposite happens. We get stuck in a 'never-ending story' that will repeatedly hurt us.

Constantly reliving negative thoughts not only threatens our psycho-physical health but will also:

• Intensify sadness
• Amplify and prolong our anger
• Exhaust us intellectually and emotionally
• Suppress motivation and hinder our ability to focus and think productively.

Therefore, when you feel your heart pounding, breathing deeply, palms sweating (if this isn't a 'normal' occurrence)... don't ask what you've done to yourself (or someone else), but what you've done to your brain.

Because it's all in your head.

And finally, when comparing brain MRI scans from the early days of its use, around the early 80s, to today, it's clear that the human brain looks much less 'tangled'. Why?

We used to spend more time alone with ourselves, thinking, reading... Digitalization has led us to wake up with our phones and go to bed with them, leaving us very little time to ourselves.