Experts say middle-aged people with iron deficiency have a higher risk of heart disease later. You can increase iron levels with diet and supplements. Health Conditions Discover Plan Connect. Medically reviewed by Gerhard Whitworth, R. How does it function? What does cardiac muscle tissue look like when it moves? What are heart muscles made of?
What is cardiomyopathy? How does exercise impact cardiac muscle tissue? The bottom line. Read this next. How Your Heart Works. Medically reviewed by Stacy Sampson, D.
Medically reviewed by University of Illinois. Medically reviewed by Debra Sullivan, Ph. Warning Signs of a Heart Attack. Medically reviewed by Elaine K. Luo, M. Is Best for Heart Health Experts say there are a number of ways to make it easier to go to bed at a proper time, including when you exercise and when you eat. Medically reviewed by Dr.
Payal Kohli, M. Medically reviewed by Avi Varma, MD. We also cover medical conditions that can affect cardiac muscle tissue and tips for keeping it healthy. Muscle is fibrous tissue that contracts to produce movement.
There are three types of muscle tissue in the body: skeletal, smooth, and cardiac. Cardiac muscle is highly organized and contains many types of cell, including fibroblasts, smooth muscle cells, and cardiomyocytes. Cardiac muscle only exists in the heart.
It contains cardiac muscle cells, which perform highly coordinated actions that keep the heart pumping and blood circulating throughout the body. Unlike skeletal muscle tissue, such as that which is present in the arms and legs, the movements that cardiac muscle tissue produces are involuntary. This means that they are automatic, and that a person cannot control them. These contract and expand in response to electrical impulses from the nervous system.
Pacemaker cells generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax. The pacemaker cells control heart rate and determine how fast the heart pumps blood. Cardiac muscle tissue gets its strength and flexibility from its interconnected cardiac muscle cells, or fibers. Most cardiac muscle cells contain one nucleus, but some have two. Cardiac muscle cells appear striated or striped under a microscope. These stripes occur due to alternating filaments that comprise myosin and actin proteins.
The dark stripes indicate thick filaments that comprise myosin proteins. The thin, lighter filaments contain actin. When a cardiac muscle cell contracts, the myosin filament pulls the actin filaments toward each other, which causes the cell to shrink. The cell uses ATP to power this contraction. A single myosin filament connects to two actin filaments on either side. This forms a single unit of muscle tissue, called a sarcomere.
Intercalated discs connect cardiac muscle cells. Gap junctions inside the intercalated discs relay electrical impulses from one cardiac muscle cell to another. Desmosomes are other structures present within intercalated discs. These help hold cardiac muscle fibers together. Some common symptoms of cardiomyopathy include :. A heart attack due to a blocked artery can cut off the blood supply to certain areas of the heart.
Eventually, the cardiac muscle tissue in these areas will start to die. However, cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain only one nucleus, which is located in the central region of the cell.
Cardiac muscle fibers also possess many mitochondria and myoglobin, as ATP is produced primarily through aerobic metabolism. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs.
An intercalated disc allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes. A gap junction forms channels between adjacent cardiac muscle fibers that allow the depolarizing current produced by cations to flow from one cardiac muscle cell to the next.
This joining is called electric coupling, and in cardiac muscle it allows the quick transmission of action potentials and the coordinated contraction of the entire heart.
This network of electrically connected cardiac muscle cells creates a functional unit of contraction called a syncytium. The remainder of the intercalated disc is composed of desmosomes.
A desmosome is a cell structure that anchors the ends of cardiac muscle fibers together so the cells do not pull apart during the stress of individual fibers contracting Figure 2.
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