Cardiac Muscle Cells

As this disease progresses and the workload of the heart is consistently increased, ventricular hypertrophy occurs. At first, the hypertrophied heart muscles will increase contractility, thus increasing cardiac output; however, as hypertrophy of the ventricular myocardial cells continues, it begins to have poor contractility, requires more oxygen to perform, and has poor circulation from the coronary arteries. This can result in heart tissue ischemia and lead into cardiac dysrhythmias (Lewis et al. 2014, 768).

The cardiac muscles are the muscle of the heart itself. The cardiac muscle is the tissue that makes

The Myocardium is made up of specialised cardiac muscle, only found in the heart and is not under voluntary control.

How does the structure of cardiac myocytes and intercalated disks follow the function of cardiac muscle tissue

The cardiac muscle consists of long branched fibres. Whereas, the brain tissue has spider web like structure. The cardiac muscle cell are made up of fibres. The function of cardiac muscle is to help the heart to pump blood. The function of brain tissue is to send messages to and from the brain. The cardiac muscle is present inside the heart. However, the brain tissue is located inside brain.

R E V I E W S H E E T 30 Anatomy of the Heart

Smooth muscles are found in the skin, internal organs, reproductive system, major blood vessels, and excretory system. Skeletal muscles are composed of long fibers surrounded by a membranous sheath, the sarcolemma. Since the Skeletal muscles are under control by whom ever they belong to are called voluntary muscles. This muscle is attached to two or more bones which are then attached to the skeleton by tendons. For example, head and neck muscles; contraction of these muscles produces facial expressions and head movements. They are also responsible for speech and swallowing. Skeletal muscles are the main muscles which move your body. Muscles nearly always work in coordinated groups; contraction of one muscle is accompanied by relaxation of another, while other muscles stabilize nearby joints. Then the last of the muscle types is the Cardiac Muscle or the involuntary muscles. Cardiac muscles are not under conscious control they do not react by a persons decision or movement. and are connected to the nervous system which are stimulated by autonomic impulses. Cardiac muscles are found in your internal organs like the heart or the intestine. For example; they include muscles that propel food through the intestine and those that control sweating and blood pressure.

There are two different types of cells in the heart- conducting cells, which carry the heart’s electrical signals and muscle cells, which are responsible for the contractions of the heart. A specific group of cells located near the top of the heart are known as the pacemaker of the heart because the rate

The ability of the heart to contract stems from its possession of the SA node (Sino atrial node) also called the pacemaker as it generates the hearts own electrical signal and allows it to contract and pump blood to the rest of the body. This gives the heart a special feature making it the only organ that is capable of working outside the body if provided with enough oxygen.

Cardiac muscle is involuntary because the heart works all the time and never gets fatigued unlike skeletal muscle which is voluntary because it is used for body movement such as sitting, walking and lifting. Skeletal muscle differs from cardiac muscle as it is multinucleated compared with cardiac muscle that is uninucleated. This means skeletal muscle have more than one nucleus and cardiac muscle has one nucleus in the muscle cells. Also, cardiac muscle has semi-spindle shape-like cells compared to skeletal muscle which has cylindrical shaped-like cells. Cardiac muscle has a good blood supply in contrast to skeletal muscle that has well- supplied nerve and blood vessels. Furthermore, cardiac muscle has 3

The structural support of heart is attributed to the extracellular matrix network of the heart. Pumping action of heart is due to the force generated by cardiomyocyte. The extracellular matrix network mainly consist of type I collagen with smaller amounts of type III collagen. This collagen network facilitates the transmission of a systolic force [9]. Tensile strength is provided by thick fibers mainly of type I collagen (85 % of total myocardial collagen). Type III collagen (11 % of the total collagen protein in the heart), forms thin fibers and is responsible for elasticity of the matrix network. Cardiac matrix network, morphologicaly can be subdivided into three constituents: the epimysium, perimysium and endomysium [10] (Figure 1). The entire cardiac muscle is enveloped by epimysium and is located on the endocardial and epicardial surface providing support for endothelial and mesothelial cells.

• pacemaker cells- are specialized cells that cause involuntary muscles and tissues to contract or dilate.

Opposed to performing heart transplants after a myocardial infarction, cell sheets can be attached to the existing cardiac muscle in order to repair the damaged tissue, sticking the sheet to the heart without sutures. The researcher’s extracted bone marrow from a pig, washed away all red blood cells with a solution, and used reverse transcription so RNA makes cDNA. These cells were placed in a petri dish until the cells floated to the top of the culture, they were then placed in a different culture set at 37 degrees Celsius where two more cell layers were added on top of them. The cell sheets were placed on 5 different pig hearts on the left ventricle either basal or apical side up, after 15-60min the sheets and heart tissue underneath were removed for analysis under a scanning electron microscope. The basal side adhered to the heart tissue better than the apical side, showing a solid connection with the heart tissue about 30 minutes after being inserted. During open heart surgery, the chest should remain open at least 30 minutes after inserting the cell sheet in order to confirm it has properly stuck to the heart tissue. This study is significant because it demonstrates progress toward effectively using cell sheets to treat the heart after myocardial infarction.

Both of these muscles expand and contract as they have complex structures so it is essential how they do this. The cardiac muscle needs the contractions to occur in order to pump blood out of the atria and into the ventricles and round the circulatory system so the structure of this muscle shows the systole of the heart. The contractions of the skeletal muscle also depend on its structure. The binding and releasing of two strands of sarcomere is how the repeated pattern of contractions occurs. ATP is used to prepare myosin for binding to allow the contractions to happen. The skeletal and cardiac muscle also both has elasticity. The elasticity is used to restore the muscles back to their original lengths which enable them to resume back to their original length once they have contracted and been stretched.

While contraction in skeletal muscle is triggered by motor neurons under central control, certain cardiac muscle variants exhibit autorhythmicity. This means that that they are capable of producing their own depolarizing electrical potential. The cardiomyocytes that are capable of producing their own electrical potentials are found in what is referred to as the electrical condition system of the heart. This system is comprised of specializes cardiomyocytes that are autorhythmic and are able to conduct electrical potentials rapidly. These specialized structures include the sinoatrial node, atrioventricular node and bundle, and Purkinje fibers.