Are there gap junctions in skeletal muscle

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 Contractions of the heart heartbeats are controlled by specialized cardiac muscle cells called pacemaker cells that directly control heart rate.

Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system ANS to speed up or slow down the heart rate. The pacemaker cells can also respond to various hormones that modulate heart rate to control blood pressure.

The wave of contraction that allows the heart to work as a unit, called a functional syncytium, begins with the pacemaker cells.

This group of cells is self-excitable and able to depolarize to threshold and fire action potentials on their own, a feature called autorhythmicity ; they do this at set intervals which determine heart rate. Privacy Policy. 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. Skip to content Muscle Tissue.

Learning Objectives By the end of this section, you will be able to: Describe intercalated discs and gap junctions Describe a desmosome. Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes. Chapter Review Cardiac muscle is striated muscle that is present only in the heart.

Cardiac cells are special, amongst the muscle types, because they are connected to each other by intercalated discs - structures that are only found in cardiac muscle cells. These can be seen in this diagram, as darkly staining irregular lines, at 90 degrees to the striped sarcomeric pattern. Intercalated discs contain three different types of cell-cell junctions:.