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Cardiomyocytes

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Cardiac muscle cell

Cardiac muscle cells or cardiomyocytes are the muscle cells that make up the cardiac muscle.

Myocyte cells contain myofibrils, consisting of long chains of sarcomeres, the fundamental contractile units of muscle cells.

Myocytes show striations similar to those on skeletal muscle cells.

The majority of cardiomyocytes contain only one nucleus, although they may have as many as four.

Cardiomyocytes are about 100μm long and 10-25μm in diameter.

Cardiomyocytes have a high mitochondrial density.

Their high mitichondrial allows them to produce adenosine triphosphate (ATP) quickly, making myocytes highly resistant to fatigue.

Cardiomyocytes generate the majority of adenosine triphosphate via oxidative phosphorylation of adenosine diphosphate from reducing equivalents in the mitochondria.
Macrophages within the heart scavenge decaying and spent Mitochondria emitted from cardiomyocytes.
Insulin has a role in modulating the metabolism of cardiomyocytes.
Glucose is the pref2242ed substrate for cardiomyocytes post prandially, but the heart prefers substrates for respiration in the fasted states are free fatty acids..
During protracted fasting, ketone bodies and amino acids contribute to the heart’s production of ATP.
There is flexibility in adaptive transition from one fuel substrate to another in myocellular homeostasis.

Two types of cells exist within the heart: cardiomyocytes and cardiac pacemaker cells.

Cardiomyocytes make up the atria and the ventricles.

Cardiomyocytes must be able to shorten and lengthen their fibers and the fibers must be flexible enough to stretch.

These characteristics are critical to a beating heart.

Cardiac pacemaker cells are distributed throughout the heart and carry impulses responsible for spontaneously generating electrical impulses for the beating heart.

Cardiac pacemaker cells also, must be able to receive and respond to electrical impulses from the brain, and must be able to transfer electrical impulses from cell to cell.

Cardiomyocytes are connected by porous junctions-cellular bridges called intercalated discs.

Intercalated discs permit sodium, potassium, and calcium to diffuse from cell to cell allowing for easier depolarization and repolarization of the myocardium.

These junctions and bridges allow the heart muscle to be able to act as a single coordinated unit.

Heart muscle cells increase in size as heart grows larger during childhood.

Cardiomyocytes are slowly turned over as we age.

Less than 50% of the cardiomyocytes are replaced during a normal life span.

Growth of individual cardiomyocytes occurs during normal heart development, and response to exercise, heart disease, or heart muscle injury such as after a myocardial infarction.

The adult cardiomyocyte has a cylindrical shape that is approximately 100μm long and 10-25μm in diameter.

Cardiomyocyte hypertrophy occurs by the creation of new sarcomere units in the cell.

With heart volume overload, cardiomyocytes grow through eccentric hypertrophy, extending lengthwise but have the same diameter, resulting in ventricular dilation.

With heart pressure overload, cardiomyocytes grow through concentric hypertrophy by growing larger in diameter but have the same length, resulting in heart wall thickening.

Myocardial cells possess the property of automaticity or spontaneous depolarization.

The very slow repolarization of the cardiac muscle cell membrane is responsible for the long refractory period.

With myocardial infarction, the loss of blood flow causes portions of cardiac tissue to die, with permanent damage.

The cardiomyopathies are characterized by disruptions to cardiac muscle cell growth and / or organization.

Cardiomyopathies can be caused by genetic, endocrine, environmental, or other factors.

Myocytolysis refers to cardiac muscle damage and is a type of cellular necrosis.

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