What Controls Heart Rate?

The rhythm of life is mirrored in the pulsating rhythm of our heart - a constant, comforting beat that indicates vitality and life. But what's behind this enduring rhythm? What controls our heart rate? 

This comprehensive guide from Carda Health unravels the mysteries of the heartbeat, bringing to light the complex mechanisms driving cardiac function. Read on to learn more about your heart and how to support its health.

What Causes the Heart To Beat?

You may be intimately familiar with the feel of your heart beating, but what about what goes on behind the curtain? Understanding the mechanisms that allow the heart to beat can help you better understand your own heart health.

The Sinus Node

Tucked away in the right atrium of the heart is a small, specialized tissue known as the sinus node. As your heart's natural pacemaker, the sinus node initiates each heartbeat and keeps the heartbeat in time by generating an electrical impulse. This impulse is the starting point of the heart's rhythm, dictating the pace at which your heart beats.

The Electrical System of the Heart

The electrical impulse created by the sinus node doesn't act alone. It's part of a complex, well-timed electrical system that guides the heart's rhythmic contractions. When the sinus node emits an impulse, it travels through the walls of the atria, causing them to contract and pump blood into your heart's lower chambers, also called the ventricles.

The journey of this electrical impulse doesn't stop there. It then arrives at the atrioventricular (AV) node, situated between the atria and ventricles. Acting as a critical relay station, the AV node momentarily delays the electrical signal. This brief pause ensures the atria have enough time to fully contract and empty their blood into the ventricles before the ventricles themselves start contracting.

The electrical signal, having passed through the AV node, now enters the Bundle of His. This bundle is essentially a highway of specialized fibers that split into right and left pathways for each ventricle and then further divide into smaller fibers called Purkinje fibers.

As the electrical impulses travel through the Purkinje fibers, they spread throughout the ventricles, instigating a powerful contraction that propels blood out of the heart and into the body. This system of organized, electrically-triggered contractions and relaxations is your heartbeat.

How Does the Autonomic Nervous System Affect Heart Rate?

The autonomic nervous system – made up of the sympathetic and parasympathetic nervous systems – also has a role to play when it comes to your heartbeat.

Sympathetic Nervous System

While our heart's internal electrical system sets the baseline rhythm, it's not the sole influencer of heart rate. Enter the autonomic nervous system (ANS), the unseen conductor that fine-tunes our heart rate based on our body's needs. 

One half of this system, the sympathetic nervous system, is like the accelerator pedal in a car. It responds to situations that require increased activity or alertness, such as physical exertion, stress, or fear.

When these situations arise, the sympathetic nervous system sends signals to speed up the heart rate. It does so by releasing norepinephrine, a neurotransmitter that acts on the sinus node and heart muscle. 

This action accelerates the pace of the electrical signals, resulting in a faster heartbeat. This rapid heart rate supplies the body with the increased oxygen and nutrients it needs to respond to heightened demands or threats effectively.

Parasympathetic Nervous System

On the other hand, the parasympathetic nervous system serves as the brake, slowing the heart rate when we're at rest or in a calm state. The primary agent of the parasympathetic nervous system influencing heart rate is the vagus nerve. This nerve releases a neurotransmitter called acetylcholine, which acts on the sinus node to slow the electrical impulses and, consequently, the heart rate.

The constant interplay between the sympathetic and parasympathetic nervous systems allows our heart rate to adapt in real time to our body's needs. This dynamic system makes our heart a highly responsive and efficient organ, capable of meeting varying demands while conserving energy when possible.

How Do Hormones Affect Heart Rate?

Hormones, the body's chemical messengers, contribute significantly to the regulation of heart rate. When the body requires a rapid adjustment in heart rate, such as during exercise or stress, hormones like adrenaline and noradrenaline are released into the bloodstream.

  • Adrenaline: Also known as epinephrine, adrenaline is often referred to as the 'fight or flight' hormone. Produced by the adrenal glands, adrenaline increases heart rate, force of heart contractions, and blood pressure, preparing the body for rapid action. 
  • Noradrenaline – or norepinephrine, works hand in hand with adrenaline, amplifying the body's response and further increasing heart rate.

On the flip side, hormones can also act to reduce heart rate. For example, high levels of the hormone acetylcholine, released by the parasympathetic nervous system, can slow heart rate. Similarly, hormones that regulate other body systems can also indirectly affect heart rate.

The interplay of these hormones, alongside the autonomic nervous system, allows for the precise regulation of heart rate according to the body's needs. This complex system underlines the incredible adaptability of your heart and the importance of maintaining heart health with solutions like those offered by Carda Health.

What Else Affects Heart Rate?

While we've explored the essential mechanisms behind heart rate, it's crucial to understand that numerous factors can influence your heartbeat. Here, we delve into three critical factors: age, exercise, and stress.


Age is a significant determinant of heart rate. Infants have a much faster heart rate than adults, which gradually slows down as they grow older. 

By the time we reach adulthood, a resting heart rate of 60 to 100 beats per minute is generally considered normal. However, highly fit individuals and athletes may have a resting heart rate below this range, a testament to their efficient and healthy hearts.


During physical activity, your heart rate increases to pump more oxygen-rich blood to your active muscles. The level of increase depends on the intensity of the exercise, your fitness level, and your maximum heart rate — a value roughly calculated as 220 minus your age. 

Engaging in regular exercise can help strengthen your heart, enabling it to pump blood more efficiently and potentially leading to a lower resting heart rate.


Emotional stress and anxiety can also cause an increase in heart rate. When you're stressed, your body goes into 'fight or flight' mode, a state of heightened arousal that signals your heart to beat faster. 

While this is a normal response, chronic stress can keep your heart rate elevated for prolonged periods, which can be harmful over time. Managing stress, alongside regular exercise, forms an essential part of Carda Health's comprehensive approach to heart health.

What Are Abnormal Heart Rates?

As important as it is to understand what controls heart rate, it's equally critical to be aware of what constitutes an abnormal heart rate, also known as an arrhythmia. Two common types of arrhythmias are tachycardia and bradycardia.


Tachycardia refers to a heart rate that's too fast, which is typically more than 100 beats per minute in adults. It can be caused by several factors, including high blood pressure, anemia, or an overactive thyroid. While tachycardia can be harmless in some cases, it may also signal a serious health condition requiring medical attention.


Contrastingly, bradycardia is when the heart rate is too slow — usually less than 60 beats per minute in adults. Bradycardia can be a sign of a strong, efficient heart in physically fit individuals or a side effect of certain medications. However, it can also indicate a problem with the heart's electrical system, which would need immediate medical attention.

How Are Abnormal Heart Rates Diagnosed and Treated?

Diagnosing abnormal heart rates often begins with your healthcare provider listening to your heart with a stethoscope. However, more detailed tests are usually needed for a definitive diagnosis. Electrocardiograms (ECG), Holter monitors, event monitors, and stress tests are some of the tools doctors use to detect and study abnormal heart rates.

Treatment for arrhythmias depends on the type and severity of the condition. Some cases might not require any treatment, while others could need medication, lifestyle changes, or even medical procedures such as pacemaker implantation or cardiac ablation.

In this context, cardiac rehabilitation programs like those offered by Carda Health can serve as invaluable support systems. Carda Health provides virtual cardiac rehabilitation, guiding you through safe and effective exercises under the watchful eye of a clinical exercise physiologist. The program also includes education about heart-healthy living, from nutritional guidance to stress management techniques.

Regardless of the nature of your cardiac event, Carda Health aims to empower you in your journey toward a healthier heart, complementing traditional treatments with a comprehensive, personalized, and convenient approach to cardiac rehabilitation. Remember, taking steps towards a healthier lifestyle can help you maintain a steady heart rhythm and overall well-being.

The Bottom Line

The complex mechanisms that control our heart rate can be fascinating. From the natural rhythm set by your sinus node to the influences of the autonomic nervous system and hormonal responses, it is evident that maintaining a healthy heart rate involves a carefully coordinated balance within our bodies.

At the same time, understanding the factors that can affect this rhythm, such as age, exercise, stress, and hormonal balance, as well as potential signs of an abnormal heartbeat, can help you monitor your heart health and overall well-being.

As a leading provider of virtual cardiac and pulmonary rehab solutions, Carda Health is committed to empowering you with knowledge and equipping you with the tools you need to better manage your heart health. Our virtual cardiac rehabilitation program is designed to provide support and guidance from our expert physiologists as you navigate the road to heart health. 

Together, we can navigate the intricacies of cardiac function, turning every heartbeat into a stride toward better heart health.


Sympathetic Nervous System (SNS): What It Is & Function | Cleveland Clinic

Parasympathetic Nervous System (PSNS): What It Is & Function | Cleveland Clinic

Heart rate: What's normal? | Mayo Clinic

Tachycardia: Fast Heart Rate | American Heart Association

Bradycardia: Slow Heart Rate | American Heart Association

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