Are cardiac muscles spindle shaped?

Smooth muscle cells are spindle shaped, have a single, centrally located nucleus, and lack striations. They are called involuntary muscles. Cardiac muscle has branching fibers, one nucleus per cell, striations, and intercalated disks. Its contraction is not under voluntary control.

Moreover, what is the structure of the cardiac muscle?

Although it is striated, cardiac muscle differs from skeletal muscle in that it is highly branched with cells connected by overlapping projections of the sarcolemma called intercalated discs. These discs contain desmosomes and gap junctions.

What are the special features of cardiac muscle?

While each cell is not very strong by itself, millions of cardiac muscle cells working together are easily able to pump all of the blood in the body through the heart in less than a minute. Cardiac muscle cells have a branched shape so that each cell is in contact with three of four other cardiac muscle cells.

Which are characteristics of cardiac muscle tissue?

Cardiac muscle is specialized tissue that is found only in the heart. It has characteristics similar to both smooth and skeletal muscle tissue, as well as specialized properties, that allow it to function with fast but sustained contractions, rapid conduction and coordinated movement.

What is the shape of cardiac muscle?

Skeletal muscle = striated, voluntary, shaped like long fibers, multinucleated. Smooth muscle = nonstriated, involuntary, shaped like almonds (tapered ends), one nucleus per cell. Cardiac muscle = striated, involuntary, branched, shaped like fibers cross-linked to one another, typically one nucleus per cell.

Is cardiac muscle cylindrical?

The skeletal muscle has a common contraction called a synctium (and no gap junctions). 2.The skeletal muscles are attached to the bone, and the cardiac muscle is found in the heart. 3.Skeletal muscle cells are cylindrical in shape, whereas the cardiac muscle cells are semi-spindle in shape.

Where is calcium stored in cardiac muscle?

The sarcoplasmic reticulum of cardiac-muscle cells is not as well-developed as that of skeletal-muscle cells. Cardiac-muscle contraction is actin-regulated, meaning that the calcium ions come both from the sarcoplasmic reticulum (as in skeletal muscle) and from outside the cell (as in smooth muscle).

Are smooth muscle cells spindle shaped?

Muscle Tissue. Skeletal muscle fibers are cylindrical, multinucleated, striated, and under voluntary control. Smooth muscle cells are spindle shaped, have a single, centrally located nucleus, and lack striations. They are called involuntary muscles.

How does the heart muscle contract?

When the muscle fibers contract, myosin pulls the actin filaments together like an accordion to shrink the muscle cell and make it contract. Cardiac muscle tissue is able to set its own contraction rhythm due to the presence of pacemaker cells that stimulate the other cardiac muscle cells.

Do smooth muscle cells have Sarcomeres?

Smooth muscle cells lack sarcomeres. Instead, actin filaments are arranged obliquely in the cytoplasm. Some filaments have their plus ends anchored at points in the plasma membrane termed dense plaques, whereas other filaments have plus ends anchored in dense bodies in the cytosol.

Where does calcium come from in skeletal muscle contraction?

In turn this triggers the sarcoplasmic reticulum to release calcium ions into the muscle interior where they bind to troponin, thus causing tropomyosin to shift from the face of the actin filament to which myosin heads need to bind to produce contraction.

What is muscle tissue made up of?

Muscle tissue varies with function and location in the body. In mammals the three types are: skeletal or striated muscle; smooth or non-striated muscle; and cardiac muscle, which is sometimes known as semi-striated. Smooth and cardiac muscle contracts involuntarily, without conscious intervention.

Which muscles have intercalated discs?

Cardiac muscle consists of individual heart muscle cells (cardiomyocytes) connected by intercalated discs to work as a single functional organ or syncytium. By contrast, skeletal muscle consists of multinucleated muscle fibers and exhibit no intercalated discs.

How does the skeletal muscle contract?

The sliding filament theory is the explanation for how muscles contract to produce force. As we have mentioned on previous pages, the actin and myosin filaments within the sarcomeres of muscle fibres bind to create cross-bridges and slide past one another, creating a contraction.

Which is the biggest muscle in the human body?

The gluteus maximus is the largest muscle in the human body. It is large and powerful because it has the job of keeping the trunk of the body in an erect posture. It is the chief antigravity muscle that aids in walking up stairs. The hardest working muscle is the heart.

Where is the cardiac muscle located?

Cardiac muscle. Cardiac muscle (heart muscle) is one of the three major types of muscle, the others being skeletal and smooth muscle. It is an involuntary, striated muscle that is found in the walls of the heart.

How many nuclei are there in a cardiac muscle cell?

Cardiac muscle cells are cylindrical cells whose ends branch and form junctions with other cardiac muscle cells. A cardiac muscle cell typically has one nucleus located near the center. Two cardiac muscle cell nuclei are indicated in the labelled image. Many more cardiac muscle cell nuclei are visible.

Which muscle tissue attaches to bone?

Skeletal muscle. Skeletal muscle is one of three major muscle types, the others being cardiac muscle and smooth muscle. It is a form of striated muscle tissue which is under the voluntary control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons.

What type of cell is a spindle shaped?

Spindle cells are of mesenchymal origin, and form the body’s connective tissue, fat, muscle, bone, cartilage and blood vessels. The name ‘spindle cell’ refers to the shape of the cell on cytology and histology.

What is released by motor neurons to stimulate a contraction?

When the nervous system signal reaches the neuromuscular junction a chemical message is released by the motor neuron. The chemical message, a neurotransmitter called acetylcholine, binds to receptors on the outside of the muscle fiber.

What causes smooth muscle contraction?

Smooth muscle contraction is caused by the sliding of myosin and actin filaments (a sliding filament mechanism) over each other. The energy for this to happen is provided by the hydrolysis of ATP. Unlike cardiac and skeletal muscle, smooth muscle does not contain the calcium-binding protein troponin.

Do cardiac and smooth muscle have T tubules?

cells do not have t-tubules & have very little sarcoplasmic reticulum. cells do not contain sarcomeres (so are not striated) but are made up of thick & thin myofilaments. Thin filaments in smooth muscle do not contain troponin.

Is cardiac tissue Multinucleated?

A unique aspect of cardiac muscle is the number of nuclei found inside the cell. Skeletal muscle cells are multinucleated from the fusion of muscle cells and smooth muscle cells are strictly mononucleated, and cardiac muscle cells are mononucleated in humans.

What attaches bone to muscle?

Tendons may also attach muscles to structures such as the eyeball. A tendon serves to move the bone or structure. A ligament is a fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.

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