Heart

Heart – The body's incredible pump From the size of the heart to the timing of heart attacks, here are the facts about the human heart everyone should know. Read on to learn little-known – but truly amazing – facts about the human heart.

Heart

The heart, which is about the size of your fist – 12 cm in length and 9 cm in width, is an incredibly efficient organ that works constantly without ever pausing to rest.

Heart is located, right in the center between the two lungs and above the diaphragm and is made of a unique cardiac muscle. The narrow end of the roughly triangular heart is pointed to the left side and during working, the contraction of the heart is most powerful at this end giving a feeling of the heart being on the left side.

The average weight of a female human heart is 9 ounces and a male‘s heart is 10.5 ounces. The heart comprises less than 0.5 percent of the total body weight. The heart has three layers. The smooth, inside lining of the heart is called the endocardium. The middle layer of heart muscle is called the myocardium.

It is surrounded by a fluid filled sac with a double walled membranous covering called the pericardium which protects the heart from mechanical injuries, while the lubricating pericardial fluid reduces friction during heart beat.

The heart is a hollow muscle that pumps blood around the body Arteries, carry oxygenated blood around the body. Veins, carry deoxygenated blood back to the heart and lungs. The large artery is the aorta, the large vein is the vena cava.

It's amazing what the human heart can do!

The movement of the blood through the heart and around the body is called circulation and the heart takes less than 60 seconds to pump blood to every cell in your body. (The lymphatic system is a part of the circulatory system, comprising a network of conduits called lymphatic vessels that carry a clear fluidcalled lymph, unidirectionally towards the heart. The lymphatic system consists of organs, ducts, and nodes. It transports a watery clear fluid called lymph. This fluid distributes immune cells and other factors throughout the body the disorders of this system also causes drastic disorders in the body.). Blood delivers oxygen to all the body‘s cells and without oxygen these cells would die. The heart is sort of a double pump, which circulates blood around the body to provide the oxygen and nutrients the body needs, while carrying away the waste. The left side of the heart receives oxygen – rich blood from the lungs and pumps it out to every part of the body.

Oxygen from blood reacts with sugar in the cells to make energy and the waste product of this process, carbon dioxide, is carried away from the cells in your blood. Blood needing more oxygen is sent back to the heart to begin the cycle again. The right side of the heart receives oxygen – poor blood from the body and pumps it to the lungs where it unloads carbon dioxide and picks up oxygen.

The right ventricle pumps the blood to the lungs, where carbon dioxide is removed from the blood and sent out of the body when we exhale. A fresh breath of oxygen through inhale enter the blood in the lungs to start the process again. The heart transports all the blood around your body about 1000 times in a day.

Blood vessels The blood vessels are the part of the circulatory system that transports blood throughout the body.

Intricate blood vessels

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart.

The right ventricle pumps blood to lungs and the left ventricle pumps blood all around the body. The muscular walls of the left ventricle are thicker than those of the right ventricle, making it a much more powerful pump. So it is easier for us to feel our heart beating on the left side of our chest.

Blood vessels play a huge role in virtually every medical condition. Cancer, for example, cannot progress unless the tumor causes angiogenesis (formation of new blood vessels) to supply the malignant cells' metabolic demand. Atherosclerosis, the formation of lipid lumps (atheromas) in the blood vessel wall, is the most common cardiovascular disease, the main cause of death. Blood vessel permeability is increased in inflammation.

Damage, due to trauma or spontaneously, may lead to hemorrhage due to mechanical damage to the vessel endothelium. In contrast, occlusion of the blood vessel by atherosclerotic plaque, by an embolized blood clot or a foreign body leads to ischemia (insufficient blood supply) and possibly necrosis (state of dying). Structural abnormality in veins causes Vasculitis, it is the inflammation of the vessel wall, due to autoimmune disease or infection.

Chambers and Valves The heart has four chambers. The two ventricles (right and left) are muscular chambers that propel the blood out of the heart (the right ventricle to the lungs, and the left ventricle to all other organs). The two atria (right and left) hold the blood returning to the heart. Each chamber has a sort of one–way valve at its exit that prevents blood from flowing backwards. When each chamber contracts, the valve at its exit opens. When it is finished contracting, the valve closes so that blood does not flow backwards.

Chambers and valves of Heart

The heart is made up of four different blood – filled areas and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium. The auricles, also called atria have thinner walls because their major function is to receive blood from the body and pump it into the very next ventricles.

The two chambers on the bottom are called the ventricles. The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum. The septum‘s job is to separate the left side and the right side of the heart.

The ventricles have thick muscular walls because they have to pump blood to long distances. The right ventricle pumps blood only up to the lungs for oxygenation. But the left ventricle pumps it up to the farthest points in the body, such as, up to the toes in the feet or up to the brain against gravity, and so its walls are thicker.

The four chambers are:

Right atrium (RA).
Right ventricle (RV).
Left atrium (LA).
Left ventricle (LV).

The atria and ventricles work as a team the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction.

Illustrating valves of the heart Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood.

Valves

Valves regulate the flow of blood in a singular direction. Each chamber has a sort of one – way valve at its exit that prevents blood from flowing backwards. When each chamber contracts, the valve at its exit opens. When it is finished contracting, the valve closes so that blood does not flow backwards.

As the valves snap shut, they make a thumping, ‘heart beat’ noise. The valves in the heart control the flow of blood within the heart.

There are four valves in the heart as follows:

The tricuspid valve is at the exit of the right atrium. Right auriculo – ventricular valve is located at the aperture between the right auricle and the right ventricle.

It has three thin triangular leaf – like flaps (cusps) and is therefore also called tricuspid valve. The apices (pi. of apex) of the flaps are held in position by tendinous cords (chordae tendinae) arising from the muscular projections of the ventricle wall known as papillary muscles.
The pulmonary valve is at the exit of the right ventricle. Pulmonary semilunar valves are located at the opening of the right ventricle into the pulmonary artery. These are pocket – shaped and three in number.
The mitral valve is at the exit of the left atrium. Left auriculo – ventricular valve is located in a similar way on the left side of the heart. It has two cusps, and is therefore called bicuspid (also mitral) valve.
The aortic valve is at the exit of the left ventricle. Aortic semilunar valves are located at the point of origin of aorta from the left ventricle. These are also three in number and pocket – shaped.

The two valves namely mitral valve and the tricuspid valves let blood flow from the atria to the ventricles. The other two are called the aortic valve and pulmonary valve, which control the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.

Blood vessels Blood vessels are intricate networks of hollow tubes that transport blood throughout the entire body.

Arteries and Veins

Blood moves through many tubes called arteries and veins, which together are called blood vessels. These blood vessels are attached to the heart. The blood vessels that carry blood away from the heart are called arteries. The ones that carry blood back to the heart are called veins.

Blood vessels entering the heart
The right auricle receives two large vessels – anterior (superior) vena cava and posterior (inferior) vena cava. Anterior vena cava (also called superior vena cava or precaval) brings deoxygenated blood from the anterior or upper part of the body including head, chest and arms. Posterior (or inferior) vena cava brings blood from the posterior or the lower region of the body including abdomen and legs. The left auricle receives 4 pulmonary veins (two from each lung) and these pulmonary veins bring oxygenated blood to the heart.

Blood vessels leaving the heart
The pulmonary artery arises from the right ventricle and carries deoxygenated blood to the lungs for oxygenation.The aorta arises from the left ventricle and carries oxygenated blood to supply it to all parts of the body.

Blood supply to heart muscles
Coronary arteries supply blood to the the heart muscles and the cardiac veins collect blood from heart walls. If there is blockage in coronary arteries or their branches there is a "deadening" of the corresponding area of heart muscles leading to "myocardial infarction" or a heart attack in popular language.

Arteries (red) and veins (blue) branch out from the heart to every part of the body. The arteries carry blood away from the heart, and the veins bring blood back to the heart. With the exception of the pulmonary blood vessels, all the arteries carry oxygenated blood and all the veins carry deoxygenated blood.

Blood Flow

The right and left sides of the heart have separate functions. The right side of the heart collects oxygen – poor blood from the body and pumps it to the lungs where it picks up oxygen and releases carbon dioxide.

The left side of the heart then collects oxygen – rich blood from the lungs and pumps it to the body so that the cells throughout your body have the oxygen they need to function properly. All blood enters the right side of the heart through two veins: The superior vena cava (SVC) and the inferior vena cava (IVC).

The SVC collects blood from the upper half of the body. The IVC collects blood from the lower half of the body. Blood leaves the SVC and the IVC and enters the right atrium (RA). When the RA contracts, the blood goes through the tricuspid valve and into the right ventricle (RV).

When the RV contracts, blood is pumped through the pulmonary valve, into the pulmonary artery (PA) and into the lungs where it picks up oxygen.

Blood now returns to the heart from the lungs by way of the pulmonary veins and goes into the left atrium (LA). When the LA contracts, blood travels through the mitral valve and into the left ventricle (LV). The LV is a very important chamber that pumps blood through the aortic valve and into the aorta. The aorta is the main artery of the body. It receives all the blood that the heart has pumped out and distributes it to the rest of the body. The LV has a thicker muscle than any other heart chamber because it must pump blood to the rest of the body against much higher pressure in the general circulation (blood pressure).

Blood circulation in Heart The right and left sides of the heart work together. The pattern described in the content (left side) is repeated over and over, causing blood to flow continuously to the heart, lungs, and body.

Blood from the body flows

to the superior and inferior vena cava,
then to the right atrium
through the tricuspid valve
to the right ventricle
through the pulmonic valve
to the pulmonary artery
to the lungs

The blood picks up oxygen in the lungs and then flows from the lungs:

to the pulmonary veins
to the left atrium
through the mitral valve
to the left ventricle
through the aortic valve
to the aorta
to the body parts

Flow of oxygenated and deoxygenated blood The difference between oxygenated and deoxygenated blood is that oxygenated has just been filled with oxygen from the lungs. Deoxygenated blood travels from the body back to the lungs to have oxygen resupplied.

Transport of blood

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis), but arteries—and veins to a degree—can regulate their inner diameter by contraction of the muscular layer. This changes the blood flow to downstream organs, and is determined by the autonomic nervous system.

Vasodilation (Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large veins, large arteries, and smaller arterioles. The process is essentially the opposite of vasoconstriction (Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries and small arterioles ), which is the narrowing of blood vessels. )

Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95‐100%) with oxygen. In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 75%. (The values are reversed in the pulmonary circulation). The blood pressure in blood vessels is traditionally expressed in millimeters of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg.

Vasoconstriction is the constriction of blood vessels by contracting the vascular smooth muscle in the vessel walls. It is regulated by vasoconstrictors (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandins), a number of hormones (e.g. vasopressin and angiotensin) and neurotransmitters (e.g. epinephrine) from the nervous system. Vasodilation is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide .

Circulation of blood Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood.

Blood Circulation in the Heart

It starts with the contraction of the two auricles (atria). The ventricles at this time are relaxing (or dilating) and are empty . Therefore, the blood from the auricles passes into the ventricles easily. When the ventricles contract, the auricles relax. The blood from the ventricles under pressure tends to return to the auricles, but the flaps of the two cuspid valves get tightened and puffed up, thus closing the passage and preventing the return of blood. The chordae tendinae hold the flaps of the valves in position and prevent their overturning into the auricles.

The only course left for the ventricular blood is to enter the pulmonary artery from the right ventricle and the aorta from the left ventricle. The mouths of the pocket – like valves at the bases of these two blood vessels face away from the ventricles. Therefore, the blood leaving the ventricles presses the valves flat and gets a clear passage in between. When the ventricles dilate, the blood from the pulmonary artery and the aorta tends to return, the blood fills the pockets of the valves and closes the passage.

Atrial Systole:

Atrial (auricular) muscles contract.
Openings of vena cava and pulmonary vein close.
Blood enters ventricles by crossing through tricuspid and mitral valves.
Semilunar valves at the roots of pulmonary artery and aorta are closed to prevent flow of blood back into ventricles.

Ventricular Systole:

Ventricular muscles contract.
Tricuspid and mitral valves close with a jerk producing the sound "LUBB".
Blood passes into aorta and pulmonary artery through semilunar valves.
Atria draw in blood through the openings of vena cava and pulmonary vein.
Chordae tendinae hold the valves in position preventing their upturning due to pressure exerted by the contracting ventricles.

Cardiac cycle The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next.

The cardiac cycle

The cardiac cycle is the sequence of events that occurs when the heart beats. The frequency of the cardiac cycle is described by the heart rate. Each beat of the heart involves five major stages. The first two stages, often considered together as the "ventricular filling" stage, involve the movement of blood from atria into ventricles. The next three stages involve the movement of blood from the ventricles to the pulmonary artery (in the case of the right ventricle) and the aorta (in the case of the left ventricle.)

Coronary arteries are the ones that we try to keep clear by eating a healthy diet. If coronary arteries are blocked a heart attack results. The heart, just like any other organ, requires blood to supply it with oxygen and other nutrients so that it can do its work.

The heart does not extract oxygen and other nutrients from the blood flowing inside it – – it gets its blood from coronary arteries that eventually carry blood within the heart muscle. Approximately 4 percent to 5 percent of the blood output of the heart goes to the coronary arteries (7½ ounces/minute or 225 ml/min). There are two main coronary arteries – The left main coronary artery and the right coronary artery which arise from the aorta. The left main coronary artery divides into the left anterior descending branch and the left circumflex arteries. Each artery supplies blood to different parts of the heart muscle and the electrical system.

Coronary circulation It is the circulation of blood in the blood vessels of the heart muscle ( myocardium). The vessels that deliver oxygen–rich blood to the myocardium are known as coronary arteries. The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins.

Coronary circulation

Coronary circulation is the circulation of blood in the blood vessels of the heart muscle (myocardium). The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins.

The coronary arteries that run on the surface of the heart are called epicardial coronary arteries. These arteries, when healthy, are capable of autoregulation to maintain coronary blood flow at levels appropriate to the needs of the heart muscle. These relatively narrow vessels are commonly affected by atherosclerosis and can become blocked, causing angina or a heart attack. The coronary arteries that run deep within the myocardium are referred to as subendocardial. The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium: there is very little redundant blood supply, which is why blockage of these vessels can be so critical.

The heart also has veins that collect oxygen – poor blood from the heart muscle. Most of the major veins of the heart (great cardiac vein, small cardiac vein, middle cardiac vein, posterior vein of the left ventricle, and oblique vein of the left atrium) drain into the coronary sinus which opens into the right atrium.

Coronary artery disease is caused by a blockage in one of the coronary arteries. When a coronary artery is partially blocked, that artery cannot supply enough blood to the heart muscle to meet its needs during exertion. When someone with coronary artery disease exerts himself or herself, it causes chest pain. This is due to lack of blood and oxygen to that part of the heart muscle and is called angina. If the obstruction worsens (more frequent angina episodes, with less exertion) a condition called unstable angina can occur. A heart attack happens when a coronary artery is completely blocked and no blood or oxygen is getting to the heart muscle served by that artery.

Analyzing heart beat During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.

Understanding blood pressure

The force which the blood exerts on the walls of the blood vessels is called blood pressure. As the heart beats, it pumps blood through a system of blood vessels, which carry blood to every part of the body. Diastolic pressure is the pressure that is exerted on the walls of the various arteries around the body in between heart beats when the heart is relaxed. Systolic pressure measures the amount of pressure that blood exerts on arteries and vessels while the heart is beating.

When we go for a checkup, doctor uses a stethoscope to listen carefully to your heart. A healthy heart makes a lub – dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart.

The first sound (the lub) happens when the mitral and tricuspid valves close. The lub sound is caused by the acceleration and deceleration of blood and a vibration of the heart at the time of the closure of the tricuspid and mitral valves. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart. The dub sound is caused by the same acceleration and deceleration of blood and vibrations at the time of closure of the pulmonic and aortic valves.

Systole and diastole The auricles contract first followed by the contraction of the ventricles. The contraction phase (systole) is followed by a relaxation phase (diastole). At the end of ventricular systole, the ventricles start relaxing (ventricular diastole). Meanwhile the atria (auricles) have also been relaxing (atrial diastole) and for a short period, both the atria and the ventricles are in a relaxed state (joint diastole). The whole sequence of events in the heartbeat is called cardiac cycle.

Systole and Diastole

Without nervous system control, the heart would beat around 100 times per minute, but when we are relaxed our parasympathetic nervous system sets a resting heart beat rate of about 70 beats per minute.

When we exercise or feel anxious our heart beats more quickly, increasing the flow of oxygenated blood to our muscles which is triggered by our sympathetic nervous system. Heart rate also increases in response to hormones like adrenalin. The maximum heart rate however would be about 220 beats per minute minus our age. So a 40 year old would have a maximum heart rate of 180 beats per minute.

Each heartbeat consists of two main steps:
The auricles contract first followed by the contraction of the ventricles. The contraction phase (systole) is followed by a relaxation phase (diastole). Each full beat of the human heart lasts for about 0.85 seconds.

At the end of ventricular systole, the ventricles start relaxing(ventricular diastole). Meanwhile the atria (auricles) have also been relaxing (atrial diastole) and for a short period, both the atria and the ventricles are in a relaxed state (joint diastole). The whole sequence of events in the heartbeat is called cardiac cycle. Rate of heartbeat varies among different species and even in individuals of the same species. Some of the variations in beats per minute in different species are as follows and the heart rate is slower if size is larger as heart has to handle large volumes of blood flowing through the same narrow terminal capillaries.

Pulse rate in different species The rate of heartbeat varies enormously between different species, ranging from around 20 beats per minute in codfish to around 600 in hummingbirds.

The Pulse

The easiest way to know the working of the heart is through the pulse. We can find our pulse by lightly pressing on the wrist, just below the thumb. The pulse (beat) is caused by the contraction (squeezing) of the heart.

We can measure the heart rate by counting number of beats we can feel in 1 minute. When we are resting, pulse rate could vary between 70 and 100 beats per minute. When the heart muscle contracts (systole), it pumps blood out of the heart.

The right and left atria contract at the same time, pumping blood to the right and left ventricles and then the ventricles contract together to propel blood out of the heart.

Then the heart muscle relaxes (called diastole) before the next heartbeat, which allows blood to fill up the heart again.

SA node ‐ The pacemaker of the heart Also known as the sinus node, the SA node is the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending electrical signals through the heart muscle, causing the heart to contract and pump blood throughout the body.

SA node - The natural pacemaker of the heart

Unlike skeletal muscle cells that need to be stimulated by nerve impulses to contract, cardiac muscle cells can contract all by themselves. However, if left to their own devices, cardiac muscle cells in different areas of your heart would beat at different rates.

Muscle cells in your ventricles would beat more slowly than those in your atria. Without some kind of unifying function, your heart would be an inefficient, uncoordinated pump. There are a special group of cells that have the ability to generate electrical activity on their own.

These cells separate charged particles. Then they spontaneously leak certain charged particles into the cells. This produces electrical impulses in the pacemaker cells which spread over the heart, causing it to contract. These cells do this more than once per second to produce a normal heart beat of 72 beats per minute.

These tiny group of cells known as the sinoatrial node is responsible for coordinating heart beat rate across your heart. It starts each heartbeat and sets the heartbeat pace for the whole heart. Damage to the sinoatrial node can result in a slower heart rate.

When this is a problem, an operation is often performed to install an artificial pacemaker, which takes over in the right atrium. The heart also contains specialized fibers that conduct the electrical impulse from the pacemaker (SA node) to the rest of the heart.

Electrical conduction in heart. Illustration of a human heart, showing the specialised tissue that conducts the electrical signals governing heart- beats. The heartbeat starts in the heart's natural pacemaker, the sinoatrial (SA) node (green). This small area of specialised muscle cells emits an electrical impulse about 70 times a minute. The impulse spreads through the muscles of the atria (upper heart chambers), making them contract, and is carried via special fibres to the atrioventricular (AV) node (orange). The AV node delays the impulse to allow the ventricles (lower heart chambers) to fill, before effecting ventricular contraction via branches of the bundle of HIS (red).

Electrical Conduction

Did you know that our heart has an electrical system? It is a bit like the electrical wiring in our home. The heart's electrical system creates the signals that tell our heart when to beat. And our heartbeat is what pumps blood throughout our body. The heart's electrical system is also called the cardiac conduction system.

The electrical impulse leaves the SA node and travels to the right and left atria, causing them to contract together. This takes 0.04 seconds. There is now a natural delay to allow the atria to contract and the ventricles to fill up with blood.

The electrical impulse has now traveled to the atrioventricular node (AV node). The electrical impulse now goes to the Bundle of His, then it divides into the right and left bundle branches where it rapidly spreads using Purkinje fibers to the muscles of the right and left ventricle, causing them to contract at the same time.

Any of the electrical tissue in the heart has the ability to be a pacemaker. However, the SA node generates an electric impulse faster than the other tissue so it is normally in control. If the SA node fail, the other parts of the electrical system can take over, although usually at a slower rate.

The S-A node normally produces 60-100 electrical signals per minute — this is your heart rate, or pulse. With each pulse, signals from the S-A node follow a natural electrical pathway through your heart walls. The movement of the electrical signals causes your heart's chambers to contract and relax. In a healthy heart, the chambers contract and relax in a coordinated way, or in rhythm. When your heart beats in rhythm at a normal rate, it is called sinus rhythm.

Graph representating an electrocardiogram (ECG). Here is an example of three heartbeats from an ECG Normally, the heart beats 60‐100 times a minute. This state is called "normal sinus rhythm" or "normal rhythm."=" Depending upon the needs of the body, it may beat faster (sinus tachycardia) due to stress or slower (sinus bradycardia) such as during sleep.

Mechanism of electrical impulse

Although the pacemaker cells create the electrical impulse that causes the heart to beat, other nerves can change the rate at which the pacemaker cells fire and how strongly the heart contracts.

These nerves are part of the autonomic nervous system. The autonomic nervous system has two parts ‐ The sympathetic nervous system and the parasympathetic nervous system. The sympathetic nerves increase the heart rate and increase the force of contraction. The parasympathetic nerves do the opposite.

All this activity produces electrical waves we can measure. The measurement is typically represented as a graph called an electrocardiogram (ECG). Here is an example of three heartbeats from an ECG:
Each part of the tracing has a lettered name:

P wave ‐ coincides with the spread of electrical activity over the atria and the beginning of its contraction.
QRS complex ‐ coincides with the spread of electrical activity over the ventricles and the beginning of its contraction.
T wave ‐ coincides with the recovery phase of the ventricles.

Electrical system abnormalities can range from minor premature beats (skipped beats) that do not require treatment, to slow or irregular beats that require an artificial pacemaker. The electrical system regulating heartbeat consists of 2 main areas of control and a series of conducting pathways, similar to the electrical wiring in a house .

The sinoatrial, or SA, node is located in the right atrium. It provides the main control and is the source of each beat. The SA node also keeps up with the body's overall need for blood and increases the heart rate when necessary, such as during exercise, emotional excitement, or illness such as fever. The SA node is sometimes called the "natural pacemaker" of the heart.
Electrical impulses leave the SA node and travel through special conducting pathways in the heart to the other controller, the atrioventricular, or AV, node. The purpose of the AV node is to provide a pathway for impulses from the atria to the ventricles. It also creates a delay in conduction from the atria to the ventricle. This causes the atria to contract first and allow the ventricles to fill with blood before they contract themselves.
The delay ensures proper timing so that the lower chambers have time to fill completely before they contract.

Create an account

Warning

There are four valves in the heart as follows:

Follow Us


Guided Tour

Get In Touch
Contact Us
support@wonderwhizkids.com
marketing@wonderwhizkids.com