Tag: heart

Categories : Cardiovascular Disease NeurologyTags :

The Heart has a ‘Brain’ of its Own

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Human heart. Credit: Scientific Animations CC4.0

New research from Karolinska Institutet and Columbia University shows that the heart has a mini-brain – its own nervous system that controls the heartbeat. A better understanding of this system, which is much more diverse and complex than previously thought, could lead to new treatments for heart diseases. The study, conducted on zebrafish, is published in Nature Communications.

The heart has long been thought to be controlled solely by the autonomic nervous system, which transmits signals from the brain. The heart’s neural network, which is embedded in the superficial layers of the heart wall, has been considered a simple structure that relays the signals from the brain. However, recent research suggests that it has a more advanced function than that.

Controlling the heartbeat

Scientists have now discovered that the heart has its own complex nervous system that is crucial to controlling its rhythm.

“This ‘little brain’ has a key role in maintaining and controlling the heartbeat, similar to how the brain regulates rhythmic functions such as locomotion and breathing,” explains Konstantinos Ampatzis, principal researcher and docent at the Department of Neuroscience, Karolinska Institutet, Sweden, who led the study.

The researchers identified several types of neurons in the heart that have different functions, including a small group of neurons with pacemaker properties. The finding challenges the current view on how the heartbeat is controlled, which may have clinical implications.

Surprising complexity revealed

“We were surprised to see how complex the nervous system within the heart is,” says Konstantinos Ampatzis. “Understanding this system better could lead to new insights into heart diseases and help develop new treatments for diseases such as arrhythmias.” 

The study was conducted on zebrafish, an animal model that exhibits strong similarities to human heart rate and overall cardiac function. The researchers were able to map out the composition, organisation and function of neurons within the heart using a combination of methods such as single-cell RNA sequencing, anatomical studies and electrophysiological techniques.

New therapeutic targets

“We will now continue to investigate how the heart’s brain interacts with the actual brain to regulate heart functions under different conditions such as exercise, stress, or disease,” says Konstantinos Ampatzis. “We aim to identify new therapeutic targets by examining how disruptions in the heart’s neuronal network contribute to different heart disorders.”

Source: Karolinska Institutet

Categories : Cardiovascular DiseaseTags :

Probing the Electrical Connections Between Heart Cells

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Photo by Robina Weermeijer on Unsplash

Harvard Medical School researchers have updated our understanding on how electrical impulses in the heart travel from cell to cell. Their findings are published in the journal Biophysics Reviews.

Disturbances of the bioelectrical processes behind heart’s rhythm can result in cardiac arrhythmias, a common ailment that can lead to illness and death.

A pacemaker within the heart takes the role of an electrical clock, signalling the heart to contract. The whole muscle moves simultaneously, because each individual cell inside of it contracts in a coordinated manner and within a short time interval.

To accomplish this, the pacemaker’s initial electrical impulse rapidly propagates through cells across the heart.

“If one cell is excited electrically and the other is not, the excited cell becomes positively charged inside, and the resting cell is still negatively charged inside. As a consequence, a voltage gradient builds up between the cells,” explained study author André Kléber. “If you have a voltage gradient and a pathway with a low electrical resistance, a local current will flow.”

The connections between cells which make up the low resistance pathway and facilitate the current flow are called gap junctions. Each is made up of numerous channels, which are formed when specific proteins from one cell connect to and fuse to the proteins from another cell. According to Kléber, the fusing proteins look like placing the tips of your fingers on one hand to the fingers on the other hand.

The researchers investigated the properties of gap junctions and connexins, their constituent proteins. Kléber explained that one reason why gap junction channels are interesting is because they are a highly dynamic system in equilibrium. The creation of the channels equals the destruction.
“The turnover is very short,” he said. “On one hand, the system is very stable during your whole life. On the other hand, if you measure it, it is constantly cycling in periods of a few hours.”

The proteins found in gap junctions are also important for processes not directly related to cell-cell connections, like mitochondrial function, which produces energy, and trafficking, which transports molecules from their synthesis site to their site of action in the cell interior.

“You have to refrain from the idea that if you define the role of a protein in the body, that it has only a single function,” said Kléber. “Nature is much, much smarter than human beings.”

Source: American Institute of Physics

Journal information: Kléber, A.G & Jin, Q., (2021) Coupling between cardiac cells—An important determinant of electrical impulse propagation and arrhythmogenesis. Biophysics Reviews. doi.org/10.1063/5.0050192.