Cardiac Muscle Tissue Anatomy & Physiology Review Lecture

Introduction to Cardiac Muscle Tissue

• Cardiac muscle tissue is one of the three types of muscle tissue found in the human body, alongside skeletal and smooth muscle tissues.

• It is specialized and unique to the heart

Characteristics of Cardiac Muscle Tissue

• The term "cardiac" means relating to the heart.

• Cardiomyocytes (cardiocytes) are the cells that comprise cardiac muscle tissue, which together form the myocardium (the muscle layer of the heart).

• The myocardium is responsible for the rhythmic contraction of the heart, facilitating blood circulation throughout the body, supplying essential nutrients and oxygen.

Similarities with Skeletal Muscle Tissue

• Cardiac muscle, like skeletal muscle, is enclosed by connective tissue known as endomysium ("endo" meaning within, "mysium" meaning muscle).

• Both muscle types feature myofibrils and sarcomeres that utilize actin and myosin filaments for contraction, resulting in a striated appearance distinguished by stripes:

  • Sarcomeres are the functional units that organize muscle filaments into zones and bands, contributing to the striated pattern.

Differences from Skeletal Muscle Tissue

• Control Mechanism:

  • Cardiac muscle contracts involuntarily (without conscious thought) through the autonomic nervous system, contrasting with the voluntary contraction of skeletal muscle.

• Cell Shape and Structure:

  • Skeletal muscle forms long cylindrical fibers, while cardiac muscle consists of single cells with an irregular branched appearance.

  • Cardiac muscle cells are connected through intercalated discs, unlike skeletal muscle.

• Nucleus Count:

  • Skeletal muscle cells contain multiple nuclei at the periphery, whereas cardiac muscle cells typically have one or two nuclei located centrally in the cell.

Intercalated Discs in Cardiac Muscle

• Intercalated discs are a vital feature of cardiac muscle, promoting connectivity and communication between cells. They contain three types of cell junctions:

  • Desmosomes:

    • Act as structural supports to hold adjacent cells together during contraction, preventing separation of muscle fibers.

  • Fascia adherens:

    • Connect and adhere to the actin filaments within cardiac muscle cells to maintain integrity and facilitate synchronized contraction.

  • Gap junctions:

    • Small channels that allow the rapid exchange of ions between adjacent cells, enabling simultaneous contraction of cardiac muscle cells through depolarization. (entering through the plasma)

• The presence of these junctions ensures coordinated heart muscle contractions, essential for effective heart function.

Pacemaker Cells

• Specialized pacemaker cells regulate heart rate by connecting to gap junctions, orchestrating the timing of muscle contractions across the myocardium.

Conclusion

• A summary of the key features and functions of cardiac muscle tissue.

• Encouragement to engage with additional resources available through linked quizzes and videos on anatomy topics.