Is the heart connected to the brain?

Imagine that you’ve gone to your local park for a run. You’re feeling the urge to pick up your pace, so your brain sends messages along the nerves in your leg muscles telling them to move faster, and suddenly you’re sprinting. But if you want to keep running at this pace, your muscles will need to be supplied with more oxygen and glucose to keep them going. This means that your heart will need to beat faster and with more force, in order to pump more oxygen-rich blood to your muscles.

We can’t consciously increase the speed or strength of our heartbeat, so this is where the subconscious part of our nervous system – known as the autonomic nervous system – is in control. It’s this process, and how it can go wrong, that Professor Alexander Gourine and his team at University College London are researching, with colleagues at Queen Mary University of London.

This process might hold part of the secret to athletic success: the fitter we are, the more effective the connections are between our brain and our heart. But more importantly, this research could help people with heart failure, and other heart and circulatory diseases that make it much harder to exercise. 

Exercise and heart disease

The autonomic nervous system controls many of the body’s functions – pretty much anything that our body does without us having to think about it, such as sweating, digestion, or the blood pressure in our arteries. One part of the autonomic nervous system is a pair of nerves called the vagus nerves, which run up either side of the neck. These nerves connect the brain with some of our internal organs, including the heart. They allow the brain to receive information about how hard the heart is working and send commands to control how quickly it beats.

It seems that if we exercise regularly, our autonomic nervous system adapts to control the heart more efficiently. When people develop heart disease, the opposite happens: the autonomic nervous system becomes less active and doesn’t talk to the heart as much. This means that the heart finds it harder to quickly and fully respond to our physical demands, leaving many people with heart disease unable to exercise.

What happens during heart failure

We know very little about exactly how exercise changes the way the brain controls the heart for the better. We’re also in the dark as to how this goes awry when people develop heart disease.

Understanding this would be of particular benefit to people with heart failure – when the heart is not pumping blood around your body as effectively as it should.

Professor Gourine explains: “People with heart failure can find it very difficult to exercise, as they get out of breath easily." 

In the future, we may be able to control and improve the activity of the autonomic nervous system using drugs or electrical devices, so that people with heart failure are more able to exercise.

Professor Alexander Gourine

In order to try to achieve this, the team will first use rats to find out how the autonomic control of the heart changes after regular exercise.

Nerve cells don’t touch each other – instead, they transmit messages around our bodies using electrical and chemical signals. These messages start in a nerve cell as electrical signals, which then kickstart chemical signals that travel between one nerve cell and the next, until it gets to its destination, such as the heart. The researchers will measure the electrical activity of the vagus nerves to ‘listen in’ on these signals and find out how the brain neurons communicate differently when you have heart disease and how this can be changed by exercise.

If we knew more about how our autonomic nervous system works, and the vagus nerves in particular, researchers might be able to develop treatments that mimic the effect of exercise on these nerves. These could help people with heart disease, by getting the brain talking to the heart more effectively.

“When it comes to our hearts, and keeping them healthy, the role of the brain is often forgotten,” says Professor Gourine. “With the BHF’s help, we’re determined to better understand the links between the brain and the heart with the aim of helping patients with heart disease to improve and maintain their physical activity – which is essential to every aspect of health.” 

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