Heart rate

Your heart beats to move blood.

This speed is called your heart rate. It changes based on what you need.

When you run, your heart goes fast. This helps your body get air. When you sleep, it goes slow.

Some people have very fast hearts. This can happen when you are stressed. Other people have very slow hearts.

Athletes often have slow resting hearts. Their hearts are very strong.

Your heart stays busy all day. It works to keep you well.

Your heart beats to move blood through your body.

This speed is called your heart rate. We measure it in beats per minute, or bpm. A normal resting heart rate for an adult is 60 to 100 bpm.

Your heart rate changes to meet your body's needs. If you exercise, your heart beats faster to help you get oxygen. If you sleep, your heart rate often drops to 40 or 50 bpm. Some people have a very slow heart rate. We call this bradycardia. An athlete might have a resting rate as low as 37 bpm. A very fast heart rate is called tachycardia. This is a rate above 100 bpm while resting.

A special part of your heart called the sinoatrial node sets the rhythm.

Your brain helps control this rhythm using nerves. One nerve uses a chemical to speed up the heart. Another nerve uses a different chemical to slow it down. This is like driving a car. The second nerve acts like a brake to keep the speed steady.

Stress or caffeine can also make your heart beat faster.

Your heart rate is the speed of your heartbeat. We measure this by counting how many times the heart contracts in one minute. This measurement is called beats per minute, or bpm.

Your heart rate is not always the same. It changes based on what your body needs at that moment. For example, your body may need to absorb more oxygen or get rid of carbon dioxide.

This constant changing helps keep your body working correctly.

A special part of the heart called the sinoatrial node, or SA node, sets the rhythm.

Your brain helps control this rhythm using two different types of nerves. The sympathetic nerves act like an accelerator to speed the heart up. They release a chemical called norepinephrine to do this. On the other hand, the parasympathetic nerves act like a brake to slow it down. They use a chemical called acetylcholine to lower the rate.

Without any nerve help, the SA node would beat at about 100 bpm. The body uses the "brake" nerve to keep the resting rate lower.

Many different things can change how fast your heart beats. Physical fitness and genetics play a big role in your natural rate. Stress or being very anxious can make your heart race. Even what you eat or drink can have an effect. For instance, caffeine and nicotine are stimulants that increase your heart rate.

On the other hand, certain drugs called sedatives can slow the rate down. Your body is always balancing these many different factors.

There are specific numbers used to describe heart rates. The American Heart Association says a normal resting adult rate is 60 to 100 bpm. If the rate is above 100 bpm at rest, it is called tachycardia. If the rate is below 60 bpm at rest, it is called bradycardia.

Some people have very different numbers. An ultra-trained athlete might have a resting rate of only 37 to 38 bpm. When you are sleeping, a rate of 40 to 50 bpm is often normal. If the heart beats in an irregular pattern, it is called an arrhythmia.

Your heart rate is connected to many parts of your daily life. You might feel your heart beat faster when you are excited or scared. This is because your brain sends signals to your heart to prepare you. You can even use slow, deep breathing to help lower your heart rate.

Scientists use tools like heart rate monitors to track these changes. Understanding your heart rate helps you learn how your body responds to the world. It is a vital sign that shows how your body is doing.

Heart rate is the frequency of the heartbeat. It is measured by counting the number of heart contractions per minute. This measurement is commonly called beats per minute, or bpm.

Maintaining a proper heart rate is essential for survival. The rate changes to meet the body's physical needs. For instance, the body must adjust to absorb oxygen and excrete carbon dioxide.

Your heart rate is often equal or very close to your pulse rate. This pulse can be measured at any peripheral point on the body.

The heart's rhythm is primarily controlled by a specialized group of cells. This group is known as the sinoatrial node, or SA node. Under normal conditions, the SA node regulates the heart rhythm entirely. However, the nervous system provides extra modulation to adjust the speed. This regulation happens through the sympathetic and parasympathetic nervous systems. These systems work together to ensure the heart meets the body's demands.

The brain manages this control through the medulla oblongata. This part of the brain contains paired cardiovascular centres. One region is the cardioaccelerator center, which stimulates heart activity. It uses sympathetic stimulation to speed up the heart. The other region is the cardioinhibitory center. This center uses parasympathetic stimulation to decrease heart activity. These two systems provide what is called autonomic tone. This is a constant, slight stimulation that keeps the heart functioning steadily.

Sympathetic stimulation works much like an accelerator in a car. The cardioaccelerator nerves release a neurotransmitter called norepinephrine. This chemical binds to beta-1 receptors on the heart cells. This process opens sodium and calcium ion channels. The influx of these positively charged ions speeds up depolarization. Consequently, the heart contracts more frequently. Conversely, the parasympathetic system acts like a brake. The vagus nerve releases acetylcholine to slow the rate. This opens potassium ion channels to slow spontaneous depolarization. Without this "brake," the SA node would naturally beat at about 100 bpm.

Specialized sensors called receptors constantly send data to the brain. Baroreceptors are stretch receptors found in the aortic sinus and carotid bodies. They monitor blood pressure by sensing how much the vessel walls stretch. When pressure increases, these receptors signal the brain to increase parasympathetic activity. This slows the heart to bring pressure back to normal. Other sensors called chemoreceptors monitor chemical levels. They detect changes in oxygen, carbon dioxide, and hydrogen ions. If carbon dioxide levels rise, the cardiovascular centres respond by increasing the heart rate.

Many external and internal factors can influence these biological rhythms. Hormones like epinephrine and norepinephrine can trigger a fight-or-flight response. These catecholamines bind to receptors to increase the heart rate rapidly. Thyroid hormones, such as thyroxine, also impact the rate over longer periods. Even diet plays a role, as caffeine and nicotine act as stimulants. Physical fitness is another major factor in heart rate variability. For example, a normal resting adult heart rate is 60 to 100 bpm. However, an ultra-trained athlete may have a resting rate of only 37 to 38 bpm.

Medical professionals use specific terms to describe abnormal heart rates. If a resting heart rate is above 100 bpm, it is called tachycardia. If the resting rate is below 60 bpm, it is called bradycardia. While a low rate can be normal for athletes or during sleep, it can also indicate issues. If the heart beats in an irregular pattern, it is called an arrhythmia. These abnormalities can sometimes be signs of heart disease. Understanding these rhythms helps scientists and doctors monitor how the body responds to stress, exercise, and illness.