Brain vs Heart: Which Should I Listen To?
Issue 5
Did you know?
Did you know that the human brain is the most complex thing in the universe? It’s basically a squishy mass of fat and protein, made up of two types of cells—neurons and glia—each in the billions! Neurons have branch-like extensions called axons and dendrites that help send messages, like when you’re deciding what to eat for lunch. Meanwhile, glial cells act like bodyguards, protecting neurons and keeping your brain in top shape. Pretty cool, right? [1]
Here’s another interesting fact about your brain. Ever wish you could blame your forgetfulness on science? Well, now you can! A fascinating new theory highlighted in Nature Reviews Neuroscience suggests that forgetting isn’t just a sign of a faulty brain—it’s actually a feature, not a bug. [2] The brain actively lets go of less relevant memories to help us adapt more flexibly to our surroundings, make better decisions, and even improves our overall well-being. This challenges the common belief that memory loss is purely a dysfunction. So, the next time someone scolds you for forgetting something important, just tell them you’re giving your brain the upgrade it needs! [3]
What about your heart then? Mondays are rough—we all know it. But did you know your heart agrees? Studies show that heart attacks are most common on Mondays, a phenomenon known as the “Blue Monday” effect. Why? Stress! The stress of transitioning from a relaxed weekend to the grind of a new workweek can mess with your body’s natural circadian rhythm, spiking stress hormones like cortisol and putting extra strain on your heart. [4], [5]. So, if Mondays feel like a heart attack waiting to happen… science says you’re not entirely wrong!
Lastly, did you know your heart has its very own "mini-brain"? It’s true! The heart is equipped with a complex network of neurons, neurotransmitters, and proteins that work seamlessly with the brain and autonomic nervous system. This system allows the heart to process information, make autonomous decisions, and adjust its rhythm to meet the body’s varying needs—without relying on constant brain input. There are three key components that make this possible: first, the Intrinsic Cardiac Nervous System, embedded within the heart's tissues, which precisely modulates cardiac activity; second, the Autonomic Nervous System, which includes the sympathetic and parasympathetic branches that enable the heart to adapt to stress and relaxation, maintaining heart variability; and third, the Vagal and Sympathetic Axons, which facilitate bidirectional communication between the heart and brain, ensuring the heart's functions are in sync with the body’s overall demands. Together, these systems work to keep your heartbeat stable, adaptable, and perfectly in tune with the rest of your body. [6]
History of the debate?
Ancient Egyptians used to believe that the heart was the centre of thought, emotions and soul and would keep the heart during mummification and instead discard the brain which was thought to have no particular use. Thus, the head remains empty post mummification, quite literally an airhead am I right? [7]
Whilst there is an unprecedented number of debates on the founder of the brain theory, many suggest that Alcmaeon of Croton, a Greek medical writer and philosopher-scientist in the 5th century BCE [8]. He theorised that the brain was the centre of control and intelligence in the body, connected by ‘Poroi’, now known as the nervous system. This belief stems from his Pythagorean belief that the brain is the source of mind, soul and logic whereas the heart is the place of formation for feelings. Not so fun fact; he was the first person to conduct a vivisection [9], [10].
After Alcmaeon, Hippocrates (460- 370 BCE), a Greek physician and philosopher, was the next to revolutionize our understanding of the brain. Hippocrates suggested the brain was the organ for interpretation and understanding. How did he realise this? Hippocrates was a physician and had observed that injuries surrounding the brain had an impact on people’s speech, thought, emotion and behaviour. He was also the first to observe the effect of epilepsy, a condition whereby neural connection in the body is severed. Hippocrates suggested that due to the severing of neural connection to the brain people were unable to function normally upon seeing the effect of trauma.
This theory was further supported by Galen, a Roman physician who studied injured gladiators and by observing any injuries surrounding the brain also realized that it impacted the sensations felt by the gladiators and their movement. Thus already, a neural system of sorts was discovered [11].
However the game changer really came in the 19th century, the next scientist we’ll discuss is known as the founding father of neurobiology. From the land of Tortillas, Spanish scientist Santiago Ramón y Cajal developed the "Neuron Doctrine" and "Neuron Polarization Theory" in the 20th century, which are the basis of neuroscience today. The neuron doctrine states that neurons are individual cells that connect with each other through synapses that transmit signals known as nerve impulses [12].
The science behind the heart?
Everyone knows the main function of the heart: to pump blood around the body. We won’t go through the entire cardiac cycle for the sake of all the physics takers out there, but here’s an overview. Oxygen-rich blood enters the heart via the pulmonary artery, and after being pumped through the left atrium and left ventricle, it comes out again via the aorta to be transported all around your body. After a trip around the body, the carbon dioxide rich, nutrient-poor blood is transported back to the heart via the vena cava, where it is eventually pumped back out through the pulmonary artery to your lungs. At the lungs, carbon dioxide is removed and oxygen absorbed from the air you breathe in, and the cycle repeats again.
There are also some lesser known functions of the heart. One of which is body temperature regulation. When you’re overexerting yourself physically and your body overheats, your heart rate increases to increase blood flow to the skin, allowing for more heat to be lost at the surface of your body to your surroundings. [13] Hence, overworking your muscles causes you to become as red as a tomato, not just because your heart is making sure all your cells have enough oxygen and nutrients for respiration, but also to ensure your body cools down fast enough before your organs fail due to overheating. [14]
The heart is also considered to have a “little brain”, a relatively smaller network of neurons capable of influencing our emotions! Studies have shown that the heart sends more signals to the brain than the brain sends to the heart. It generates an electromagnetic field that is 60 times stronger in amplitude than that of the brain. Also, the heart has been found to have influence over pain, fear, and feelings of love. Yes, the heart itself can produce oxytocin, which is one of the primary hormones responsible for social bonding and emotional attachment. This can possibly be a scientific justification for why the heart is a symbol of love. [15] Additionally, the heart produces a hormone called atrial natriuretic peptide (ANP), which reduces stress. For this reason, ANP may prove to be a possible solution for the treatment of alcohol dependence in patients exhibiting high levels of perceived stress. [16]
This idea of emotions truly being “held” by the heart holds true in the case of heart transplants as well. Studies indicate that heart transplant recipients may exhibit preferences, emotions, and memories resembling those of the donors, suggesting a form of memory storage and neurological imprints of emotions within the transplanted organ. [17]
Some would argue, the brain sends signals to control the heart, so without the brain, the heart wouldn’t be able to function. That may be true, but only to a certain extent. The heart actually has a sinus node, sometimes called the heart's "natural pacemaker." Every time the sinus node generates a new electrical impulse, that impulse spreads out through the heart's upper chambers, called the right atrium and the left atrium, causing the heart to beat. [18] This is the reason why when a person has confirmed brain death, the heart can continue to beat as long as it has oxygen. [19] Talk about being a strong independent organ!
Now for the science behind the brain!
The brain has many parts that help with ensuring your body can function. There are 3 main parts of the brain to learn about when considering decision making: the prefrontal cortex, the amygdala and the striatum. The prefrontal cortex is located just behind your forehead. It's responsible for logical thinking, planning, and weighing the pros and cons of different choices. The amygdala lies deep within the brain. It processes emotions like fear and pleasure, influencing how we react to various situations. The striatum is all about habits. It helps form routines and is involved in reward-based learning, guiding our decisions based on past experiences. [20]
[21]
Our decisions are also guided by our brain's chemical messengers. They are neurotransmitters. Essentially, they are chemical substances that help to transfer information and impulses around the body. In the case of decision-making in the brain, dopamine and serotonin transfer information about what we know to influence decisions made. Dopamine, the ‘feel good’ chemical, prods us towards seeking reward. [22] In today's globalised, internet-based world, where we’re constantly eating feel-good, unhealthy, ultra processed food and consuming massive amounts of short-form media, dopamine often prods us towards chasing temporary, short-lived rewards. Just imagine if we only had dopamine as a chemical messenger in our body. We would be stuck chasing pleasure and rewards all the time. Our society would not be functioning and the world we know today would not exist. To ensure this does not happen and to counter dopamine, serotonin is another chemical messenger in our brain. It helps regulate mood and impulse control. Balanced serotonin and dopamine levels can lead to more thoughtful decisions, while excesses of dopamine might result in impulsivity. [23]
Other things that help the brain make choices are stress, past experiences and social norms. High-pressure situations can flood the brain with stress hormones. [24] This decreases our ability to think clearly because it initiates our body’s ‘fight-flight-freeze response’. [25] This primal response can often lead to more animalistic, hasty decisions being made as it disregards the prefrontal cortex, which helps us think clearly and focuses instead on the amygdala, which is impulse-driven. [26] Our brains often rely on previous outcomes to guide current decisions. Positive past experiences can encourage similar future choices, while negative ones might deter us. This can be attributed to the striatum, which helps us ‘learn from our mistakes’ and makes habits for us when an experience goes well. [27] Interactions with others can also shape our decisions. For example, group dynamics and societal norms can impact individual choices. [28] The need to be liked and to conform is often caused by parts of our frontal cortex, and also contributes to increasing our dopamine levels, i.e., making us happy. [29] Hence, we attempt to be viewed positively by others.
Which has more “control”?
The debate of heart vs brain has been around for around 2500 years. Although the key point of discussion previously was about the location of the soul and all mental processes in the body. However, the discussion has shifted away from the location today, and focuses more on which organ has a greater impact on the body. So then which one has more control on us?
It all boils down to the aspect of functions based on which you are deciding the extent of control of the organ. Say you are talking about the type of control the organ possesses over the body systems. The brain has central control over both voluntary and involuntary actions. It processes information, integrates sensory input, and makes decisions based on that. It also regulates movement, speech, thought, and autonomic functions through the nervous system. The brain hence has high- level regulatory control over the entire body. The heart however, has a more localized and mechanical control of a single, essential process: pumping blood throughout the body. In this case, the brain is more important and has greater control than the heart as the brain has a broader, multisystem control, allowing it to process more information and adjust multiple physiological responses, and manages the overall coordination of not only the heart but also other bodily systems, while the heart provides a localized level of decision-making that ensure the heart continues functioning optimally.
However, if you talk about immediate life support, the heart may be considered more important than the brain. This is because the heart pumps blood throughout the body, ensuring that oxygen reaches organs, tissues and the brain. The brain requires continuous blood flow to function properly, which makes it highly dependent on the heart for delivery of oxygen and nutrients. If the heart stops pumping blood, the brain will lose its supply of oxygen within seconds, leading to unconsciousness and eventually brain death. However, even if the brain stops functioning, the heart will still continue to beat on its own for a short time, provided the circulatory system is still intact. Hence, in this case the heart would be considered to have greater control and impact the body more than the brain.
Therefore, the issue of whether the brain or heart is more important is subjective to their specific functions and it cannot be solely based on emotional bias, where some would associate the heart with love and emotion whereas the brain is associated with consciousness and intellect. It also cannot be based on surface - level observations of their functions and have to be analyzed thoroughly as they are highly interwoven and dependent on each other.
How this affects us
So why does it matter? Well, in this extremely polarized world there are those who radically claim that we should only listen to the heart and those who say the same for the brain. Biologically, the heart does not have much influence on our emotional state and most of the emotions we feel and experience come from the hormones in our brain.
The only “emotional” response that our heart is involved in is the release of oxytocin, the love hormone. Oxytocin causes the reduction in contraction of peripheral arteries, which reduces the overall blood pressure in your blood vessels. However it does cause a contemporary sharp increase in your heart rate, which explains why your heart skips a beat when you see your eye candy. [30]
In addition to oxytocin, the heart connects to the brain through the vagus nerve. The vagus nerve carries impulses between the brain, heart and the digestive system and is the key to relaxation. The vagus nerve improves blood flow to important areas of the brain, organizes electrical patterns during seizure and boosts neurotransmitters. Such functions overall contribute to the mood. [31]
In contrast the brain is more like headquarters for all emotions (did you get the inside out reference?). The brain contains numerous hormones that act as chemical messengers and stimulating changes or reactions that we know as emotions. For example, fear is stimulated by the amygdala, followed by the hypothalamus, which is why those with brain damage at the hypothalamus may not feel fear. Happiness, on the other hand, originates partly in the limbic cortex (The limbic cortex integrates the sensory, affective, and cognitive components of pain and processes information regarding the internal bodily state). Another area called the precuneus also plays a role. The precuneus is involved in retrieving memories, maintaining your sense of self, and focusing your attention as you move about your environment [32].
Either way, both heart and brain are involved in affecting our feelings at the time and we should not neglect one or the other and instead learn to prioritise when we should listen to them respectively.
Questions to respond to:
In your opinion, which one should we listen to more?
Do you think humans will one day evolve to only listen to one?
Answer these questions on our Google Form, best entries will be featured on our Instagram page!
References:
[1] Zuckerman, C. (2009, October 15). Human Brain: Information, Facts and News. Science. https://www.nationalgeographic.com/science/article/brain-2
[2] Nature Reviews Neuroscience. (n.d.). Nature. https://www.nature.com/nrn/
[3] 7 Fascinating facts about neuroscience and the brain: How well do you know your brain? | Penn LPS Online. (2023, May 3). Lpsonline.sas.upenn.edu. https://lpsonline.sas.upenn.edu/features/7-fascinating-facts-about-neuroscience-and-brain-how-well-do-you-know-your-brain
[4] British Heart Foundation. (2023, June 9). Why are serious heart attacks more likely on a Monday? Www.bhf.org.uk. https://www.bhf.org.uk/informationsupport/heart-matters-magazine/news/behind-the-headlines/heart-attack-monday
[5] Fun Facts About Your Heart. (n.d.). Cleveland Clinic. https://health.clevelandclinic.org/fun-facts-about-your-heart
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[21] FIGURE 1. Corticolimbic Connectivity Involving the Frontal Cortex,... (2024). ResearchGate. https://www.researchgate.net/figure/Corticolimbic-Connectivity-Involving-the-Frontal-Cortex-Amygdala-and-Hippocampus_fig1_280630286
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[31] Cleveland Clinic. (2022, March 16). Vagus Nerve Stimulation. Cleveland Clinic. https://my.clevelandclinic.org/health/treatments/17598-vagus-nerve-stimulation
[32] Seladi-Schulman, J. (2018, July 23). What Part of the Brain Controls Emotions? Fear, Happiness, Anger, Love. Healthline. https://www.healthline.com/health/what-part-of-the-brain-controls-emotions#happiness