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Cardiac Muscle In The“Heart” of Muscles Introduction • Take a look the instruments that are laid out before you • These instruments are called stethoscopes • They are used to allow a person to listen inside of the human body • Since they are going to highly amplify sounds, please be careful when they are in your ears Introduction • Lets try to listen to the five major places a doctor will listen to a heart beat Introduction • What was the sound that you heard? • Can anyone describe it? • Was there one sound or two different sounds? • Why was there multiple sounds? • What is the purpose of these sounds? Cardiac Muscle • Cardiac muscle is located in the heart and is structurally different from skeletal muscle • However it works on the same basic principals • Contraction at pull on the Z line of each sarcomere making each sarcomere shorter • This overall reduces the size of each muscle fiber cell Cardiac Muscle • Each cardiac muscle cell is small compared to a skeletal muscle cell • Most also only contain one nucleus that powers each cell • A few will have two or more nuclei • Cardiac muscle cells are almost completely dependent on aerobic metabolism Intercalated Discs • Each cardiac muscle cell connects to several others at sites called intercalated discs • These play a vital role in contraction between cardiac muscle cells • They can be seen as dark lines between each muscle fiber Intercalated Discs • Intercalated discs are elaborate connections at the boundaries of each cell • These allow the cell to move small molecules between the cells so they can share materials and information • This also allows an action potential to travel from one cell to the next very rapidly Intercalated Discs • Since they are chemically, mechanically and electrically connected the heart muscle cells work like one large organ • This allows the entire system of cells to beat at once, maximizing their potential • This process is called functional syncytium (fused mass of cells) The Heart • The main organ that circulates blood around the body is the heart • The heart is a four chambered organ that uses two chambers to force blood to the lungs and two chambers to force blood to the rest of the body The Heart • When looking at a heart you can tell that not all four chambers are the same • Each side of the heart is divided to an upper and lower part • The atriums are the blood collecting chambers in the heart • The ventricles are the blood pumping chambers in the heart The Heart • The heart is divided by the septum • This is a wall of muscle that separates the atriums and ventricles • Valves are flaps of tissue that separate the sections of the heart • These flaps prevent the different sections of blood from mixing How the Heart Pumps • The heart has to have a very systematic pattern for how it beats • This keeps the blood flow to the body regular and constant • There are a few steps to the heart pumping How the Heart Pumps • It is important to remember that when the heart pumps it has two different stages • First the atriums contract together • After they contract the ventricles contract together • This gives a heart beat a distinct “lub – dup” sound Path of Blood • 1. Deoxygenated (DOX) blood enters the heart through the right atrium • This is the main collecting chamber from the body • 2. The DOX blood is forced into the right ventricle when the atriums contract Path of Blood • 3. The ventricles contract and send the blood to the lungs • After the blood returns from the lungs it is oxygenated (OX) • 4. The OX blood from the lungs then collects in the left atrium Path of Blood • 5. The atriums pump and send blood down to the left ventricle • The left ventricle is the strongest part of the heart • 6. The ventricles then pump. This sends blood to the various parts of the body Electrical Systems • The heartbeat is controlled by electrical systems • The heart only beats when there is an electrical current that tells it how and why to beat • When this electrical impulse is moving and regular, people have a normal heartbeat Electrical Systems • The SA node is a group of cells on the right atrium that initiate their own electrical signal • This signal regulates the heartbeat • It also tells the atriums to contract • When this group of cells does not work correctly, a pacemaker is installed Electrical Systems • The AV node is located in the septum and collects signals from the SA node • This tells the ventricles when to contract • This grouping of cells is reactive and relies on the information that is passes on to it from the SA node • http://www.youtube.com/watch ?v=H04d3rJCLCE Reading a Heartbeat • If the heart is not functioning properly, there can be changes to the oxygen levels of cells • Because this can lead to several serious complications, machines called electrocardiograms (EKG or ECG) read the electrical signals that control the heart • Reading these can help a medical professional understand what is wrong with a heart Reading a Heartbeat • The first reading on the EKG is the P Wave • The P Wave indicates the atria are contracting and pumping blood to the ventricles • The second reading, the QRS Waves, indicate the depolarization and contraction of the ventricles • The T Wave represents ventricular repolarization Reading a Heartbeat • Any deviations in the EKG can show a medical professional if there are some abnormalities in the heart • These simple charts can show a medical professional what condition the patient is in, how to treat the patient or how long the patient can go without care