Davis AT Collection. Davis PT Collection. Murtagh Collection. About Search. Enable Autosuggest. You have successfully created a MyAccess Profile for alertsuccessName. Home Books Junqueira's Basic Histology, 14e. Previous Chapter. Next Chapter. In: Mescher AL. Mescher A. Anthony L. Junqueira's Basic Histology, 14e. McGraw Hill; Cardiac muscle cells contract autonomously and involuntarily.
Smooth muscle is involuntary. Each cell is a spindle-shaped fiber and contains a single nucleus. No striations are evident because the actin and myosin filaments do not align in the cytoplasm.
You are watching cells in a dish spontaneously contract. They are all contracting at different rates, some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at. The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract.
When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony. Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin. Skip to content Learning Objectives Describe the characteristics of muscle tissue and how these dictate muscle function.
By the end of this section, you will be able to: Identify the three types of muscle tissue Compare and contrast the functions of each muscle tissue type. External Website. Chapter Review The three types of muscle cells are skeletal, cardiac, and smooth. Cardiac muscle is striated muscle that is present only in the heart.
Cardiac muscle fibers have a single nucleus, are branched, and joined to one another by intercalated discs that contain gap junctions for depolarization between cells and desmosomes to hold the fibers together when the heart contracts.
Pacemaker cells stimulate the spontaneous contraction of cardiac muscle as a functional unit, called a syncytium. What would be the drawback of cardiac contractions being the same duration as skeletal muscle contractions? An action potential could reach a cardiac muscle cell before it has entered the relaxation phase, resulting in the sustained contractions of tetanus. If this happened, the heart would not beat regularly.
How are cardiac muscle cells similar to and different from skeletal muscle cells? Cardiac and skeletal muscle cells both contain ordered myofibrils and are striated. Cardiac muscle cells are branched and contain intercalated discs, which skeletal muscles do not have.
It consists of long multinucleate fibers. The fibers run the entire length of the muscle they come from and so are usually too long to have their ends visible when viewed under the microscope. The fibers are relatively wide and very long, but unbranched. Fibers are not individual cells, but are formed from the fusion of thousands of precursor cells. This is why they are so long and why individual fibers are multinucleate a single fiber has many nuclei.
The nuclei are usually up against the edge of the fiber. There are striations in skeletal muscle.
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