HEARTS & MINDS
Your heart beats around 100,000 times a day, and scientists are discovering that every single beat manipulates your brain. A healthy heart, it seems, does far more than provide the pulse which supplies blood to every part of your body.
Poets say that when we are in love, the heart rules the mind. It turns out they are right, and the bloodpumping organ’s influence is not limited only to, er, matters of the heart.
SCIENTISTS HAVE
DISCOVERED NEW
LINKS SHOWING
HOW THE HEART
CONTROLS THE
BRAIN’S THOUGHTS.
3-4 billion heartbeats take place during an average lifetime.
“Their eyes met across a crowded room. Somewhere deep within their limbic brain centres, they both felt that they were made for each other.” Love stories were never quite the same once scientists relegated emotions from their ancient home in the heart to the body’s calculating computer, the brain. But new research is revealing that earlier authors may have been more accurate than we thought in ascribing our thoughts and emotions to the heart. We are now learning that the heart manipulates the brain via neurotransmitters and nerve pathways – in perfect step with our heartbeats. Scientists used to consider the heart a simple blood pump, but the new discoveries show that the heart can influence your senses, needs and deepest emotions concerning other people. So strong are the links between the human body’s two most important organs that the result comes close to a merging of duties.
Heart and brain communicate
Your pulse rate increases when you fall in love, or when you are afraid, or experience stress. You may clearly feel the beating against the inside of your chest, or the pulse of blood in your ears. In this way your heart lets you physically sense your emotions, and perhaps that is why people of different cultures have believed for millennia that emotions are based in the heart.
Over recent centuries, however, science has reduced the heart to a mechanical pump that exists simply to satisfy the body’s needs for oxygen and nourishment. If your pulse rate increases when you are in love, scientists told us that the heart was blindly obeying orders from the brain. But this view is gradually being reversed. According to recent research, the contractions of the heart are doing far more than just passing oxygen and nutrition through the body.
The heart typically contracts 60-90 times a minute. As the heart contracts, the blood is pumped first from the heart’s two atria to the two ventricles, after which the right ventricle sends its blood on to the lungs, while the left one sends its blood into the entire body. All the work is performed by muscle cells, and indeed the heart is basicaly one big autonomous muscle.
Scientists have long known that the heart controls its own rhythm, and that nerve links to the brain mean that the brain can monitor heartbeats and influence them if necessary. But over recent decades, scientists have realised that communication also flows in the opposite direction. Studies have revealed that the heart can influence a wide range of brain activities, contributing to the formation of thoughts and behaviours.
Vital hormone
The heart’s manipulation of the brain uses different communication channels. One of them is the atrial natriuretic peptide hormone ANP, which is secreted by special cells in the heart’s right atrium as the heart muscles contract. ANP’s primary purpose is to lower the blood pressure, and the heart constantly regulates the quantity of the hormone so that blood pressure remains normal.
But ANP aso affects many of the body’s organs. It enters deep into the brain, where it obstructs signals to brain areas that control thirst, so that you feel less thirsty. The heart reduces your body’s fluid level and so further controls your blood pressure.
The same hormone also restricts the sympathetic nervous system, which normally puts your body into a state of alert in dangerous situations. The nervous system can increase your pulse rate or the adrenal glands’ secretion of adrenaline, both of which prepare your body for flight or fight. By impeding the process, ANP calms you and makes you less likely to feel fear, again restraining your blood pressure. So, the heart can directly influence how you react when your life is in danger.
Studies from Japan’s Kyushu University further indicate that ANP can reduce the secretion of the stress hormone cortisol.
High levels of cortisol in the blood could harm stem and nerve cells in the brain, and increase the longterm risk of mental conditions such as anxiety and depression. So the heart contributes to mental health.
ANP’s positive effect has made scientists consider whether it can be used as a drug, perhaps for people with elevated blood pressure. But it is proving not to be an easy task. Too much of the hormone could harm several body organs, including the heart itself. But scientists hope that over the next few years they will be able to find a solution that can harness ANP’s positive effects to treat different cardiovascular diseases.
Heartbeat relieves pain
The heart has other tools that can affect your brain. One of these can increase your pain threshold, so you feel less pain. In an experiment carried out by British scientists, test subjects were subjected to pain via electrical stimulation of calf nerves. At the same time, electrodes recorded their pain reflex in the thigh muscle, and a blood pressure meter monitored their blood pressure and pulse rate. The results clearly demonstrated that the test subjects felt less pain when their nerves were activated during the heart’s contraction phase.
The scientists linked the reduced sensation of pain with the brief expansion of the blood vessels that occurs as the heart contracts and pumps blood into the body. They believe that it is the blood vessels’ own pressure meters, the baroreceptors, that provide the link between the brain’s pain centres and the heart. Baroreceptors are nerve cells that are in direct contact with blood vessels, and are activated when blood vessels expand with the rhythm of the heart. The activation triggers signals to the brain, which briefly increase your pain threshold. Other experiments reveal that the reduced sensation of pain could in some cases become chronic. When scientists studied rats that suffered from genetically-determined elevated blood pressure, they discovered that the rats had a higher pain threshold than rats with normal blood pressure. This is probably because the elevated blood pressure overactivates the baroreceptors. The same seems also to be true for people with elevated blood pressure.
If the blood pressure is elevated for long periods of time, however, the system could become overloaded so that the baroreceptors lose their sensitivity and reduce their activity due to overstimulation. Several studies show that this can instead cause chronic pain.
Stable rhythm dulls the senses
The link between heartbeat and the sensation of pain might seem odd, but scientists have a good explanation. All body organs send signals to the brain which disguise their own activity, ensuring that your consciousness doesn’t respond constantly to what is going on inside the body. By increasing the pain threshold during heartbeats, the heart helps you ignore its constant beating, so you can focus on external influences.
The heartbeat not only influences the sensation of pain, but probably also your senses in general. In 2020, brain researchers from the Max Planck Institute for Human Cognitive and Brain Sciences in Germany subjected a number of test subjects to very mild electric shocks, while electrodes recorded their heart and brain activity. Again the experiment revealed that the brain partly ignored the shocks when they were given at the same time as the heart contracted. But the scientists could also see that a series of signals in the brain which normally increase the awareness of sensory impressionx were suppressed during the heart’s contraction.
They also noted that the blocking of such sensory impressions was most efficient when the cardiac rhythm was stable. This indicates that the body’s ability to suppress the senses improves when the brain is able to predict the next heartbeat accurately.
Another curious result was that the sensation of the electric shock was further dampened when the test subjects were deliberately focusing on what was going on inside their own bodies at the same time.
Signal intensifies emotions
Focusing on your own heartbeats activates a series of brain areas which are involved not only in processing sensory impressions, but also in shaping your innermost emotions. In another experiment, German scientists tested test subjects’ ability to feel their own heartbeats. Then the subjects looked at pictures that were designed to cause either pleasant, neutral, or unpleasant emotions. Brain activity recording revealed that those people who were particularly good at focusing on and feeling their heartbeats also reacted more strongly to the pictures. This is probably because they receive a stronger signal from the heart during contraction. So even though the heartbeat relieves pain and dulls the senses, it could also bring you into closer contact with your emotions. Such contact also affects your ability to under
stand other people’s emotions. The brain networks that process your own emotions are roughly the same as the ones that help you interpret other people’s emotions. And experiments have shown that we react more strongly if we see a person who shows signs of fear or distrust at the moment that the heart contracts, rather than the moment when it expands.
Sensitive heart can cause anxiety
The heart – and the other organs – greatly influence brain activity, and the interaction is extremely important. The stomach lets the brain know when it is empty, causing a feeling of hunger, whereas a full bladder can all but force you to find a toilet. On the other hand, we can face major problems if these links to the brain are poor. Such problems are observed in some people with autism. They do not notice their own body’s signals until they become very strong. The result can be that they don’t feel annoyance until they suddenly explode in anger. In rare cases they can break a leg without feeling pain.
On the other hand, an unusually strong link between organs and brain might also cause problems. One experiment indicated that people who proved particularly good at feeling their own heartbeat also tended to feel more anxious.
Grief really can break your heart
Scientists are still a long way from understanding the complex interaction between the heart and the brain. But it is already clear that the two organs function as one unit in many ways. So the heart could very well play a role when we fall in love.
However, the newly-revealed influence of the heart on your emotions could also flow in the opposite direction, with your emotions physically affecting your heart. This can happen in a dramatic way when intense grief, such as in connection with death or divorce, causes stress cardiomyopathy or ‘broken heart syndrome’. The condition involves chest pain and breathing problems, and it probably develops because grief causes excessive secretion of adrenaline, which harms cardiac blood vessels and muscles. Thankfully most patients recover after a few weeks. As in many love stories, it seems that that the best remedy against a broken heart is time.
The revelation of the strong mutual link between the heart and the brain is well on its way to reviving our former belief that the heart is the home of some of our strongest emotions. But our hearts shouldn’t get all the credit. Our intestines, for example, may also be influenced by sadness, by happiness, and by our relationships with other people. The intestines also manipulate our thoughts via nerve links and hormones, and – as we’ve seen in previous issues – possibly also via intestinal bacteria that migrate to the brain. In the future, then, love stories should consider not only the role of the heart, but also what we feel in our gut.