Cardiac Muscles – Properties, Functions, Action Potential and Difference with Skeletal Muscles
Cardiac muscle is made up of cells called cardiomyocytes. These cells are responsible for the contraction of the heart and have many functions such as pumping blood, regulating blood pressure, and controlling breathing. Cardiomyocytes are encased by an elastic membrane that allows them to contract but also relaxes to allow them to fill with blood when they need to pump it out.
Properties of Cardiac Muscles
Cardiac muscle has a unique striated appearance, and they are able to contract much faster than skeletal muscles.
This is because they have an increased number of mitochondria, which provide more energy for contraction.
Cardiac muscle cells also have a specialized system called an endomysium which allows them to contract without disrupting neighboring cells.
What is the Specific Function of Cardiac Muscle
The cardiac muscle is responsible for pumping blood throughout the body, which includes oxygenating and removing waste products from the body.
It also helps with digestion and regulates blood pressure.
Cardiac muscle is a type of striated muscle tissue found in the heart, and it has a unique ability to contract and relax quickly.
The cardiac cycle begins with relaxation, which allows blood to fill the ventricles and then ends with a contraction that pushes blood out of the heart to all parts of our body.
The function of cardiac muscle is to pump blood throughout the circulatory system. Cardiac muscles contract and relax quickly.
Difference Between Cardiac and Skeletal Muscles
Cardiac muscles are different from skeletal muscles because they are involuntary whereas skeletal muscles are voluntary.
Cardiac muscles have a single nucleus, whereas skeletal muscles have multiple nuclei.
Cardiac muscle is also composed of cells that contain only one particular type of protein called myosin, while there are many types of proteins in skeletal muscle cells.
In contrast to skeletal muscle, cardiac muscle cells are usually branched and often have a complex organization.
Skeletal muscles are attached to bone and move the bone as they contract. Cardiac muscles are not attached to bone and instead move the blood around the body as they contract.
The cells in cardiac muscles are connected by intercalated discs which allow for rapid transmission of action potentials from cell to cell. Unlike skeletal muscles, these cells do not contain myofibrils.
Why cardiac muscle cannot be tetanized?
The heart is a muscle that cannot be tetanized. It is made up of cardiac muscle cells which are different from skeletal and smooth muscles. Cardiac muscle cells are found in the walls of the heart and they contract to pump blood throughout the body. The cells do not have a central nucleus, which is what makes them different from other types of muscles.
Cardiac muscle cells are also unique because they contain T-tubules, which allow for rapid transmission of action potentials across the cell membrane. This means that cardiac muscle can contract more quickly than other types of muscles, which is why it cannot be tetanized.
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Action Potential in Cardiac Muscles
Cardiac action potentials travel in the following order through the conduction system:
- The sinoatrial (SA) node, which is positioned in the right atrial wall just inferior and lateral to the opening of the superior vena cava, is where cardiac excitation usually starts. The resting potential of SA node cells is not constant. Rather, they depolarize to threshold on a regular basis. A pacemaker potential is a spontaneous depolarization. An action potential is triggered when the pacemaker potential hits a certain level. Gap junctions in the intercalated discs of atrial muscle fibers carry each action potential from the SA node throughout both atria. The two atria contract at the same time after the action potential.
- The action potential travels down atrial muscle fibers to the atrioventricular (AV) node, which is positioned in the interatrial septum immediately anterior to the coronary sinus opening. As a result of different differences in cell structure in the AV node, the action potential slows significantly. The atria have more time to empty their blood into the ventricles because of the delay.
- The action potential travels from the AV node to the atrioventricular (AV) bundle (also known as the bundle of His, pronounced HIZ). Action potentials can only travel from the atria to the ventricles through this bundle. (The fibrous framework of the heart electrically separates the atria and ventricles elsewhere.)
- The action potential enters both the right and left bundle branches after propagating through the AV bundle. The bundle branches reach the apex of the heart through the interventricular septum.
- Finally, Purkinje fibres with large diameters (pur-KIN-j) rapidly carry the action potential from the apex of the heart to the rest of the ventricular myocardium. The ventricles then constrict, forcing blood upward toward the semilunar valves.
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