Summary 10.7 Cardiac Muscle Tissue - Anatomy and Physiology 2e | OpenStax openstax.org
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The cardiac muscle tissue in the heart pumps blood, has a striated appearance, is branched, and contains intercalated discs with gap junctions.
Slides
Slide Presentation (7 slides)
Key Points
- Cardiac muscle tissue is found only in the heart and is responsible for pumping blood into the circulatory system.
- Cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain one nucleus.
- Cardiac muscle fibers are extensively branched and connected to each other by intercalated discs.
- Intercalated discs contain gap junctions that allow for the quick transmission of action potentials and the coordinated contraction of the heart.
- Pacemaker cells control the heart rate and respond to signals from the autonomic nervous system and hormones.
- Cardiac muscle has a sustained depolarization plateau, which allows for longer contractions compared to skeletal muscle.
- Ca++ entry from outside the cell plays a significant role in initiating contraction in cardiac muscle.
Summaries
19 word summary
Cardiac muscle tissue pumps blood in the heart. It is striated, branched, and contains intercalated discs with gap junctions.
63 word summary
Cardiac muscle tissue is responsible for pumping blood in the heart. It is striated, shorter, and usually contains one nucleus. Cardiac muscle fibers have numerous mitochondria and myoglobin for ATP production. They are extensively branched and connected by intercalated discs, which contain gap junctions and desmosomes. Specialized pacemaker cells regulate heart rate. Calcium for cardiac muscle contraction mainly comes from outside the cell.
139 word summary
Cardiac muscle tissue is responsible for pumping blood in the heart. It is striated and organized into sarcomeres, although the fibers are shorter and usually contain only one nucleus. Cardiac muscle fibers have numerous mitochondria and myoglobin for ATP production through aerobic metabolism. They are extensively branched and connected by intercalated discs, which allow for coordinated contractions. Intercalated discs contain gap junctions for depolarizing currents and desmosomes to prevent pulling apart during contraction. Specialized pacemaker cells regulate heart rate by responding to signals from the autonomic nervous system and hormones. These self-excitable cells depolarize and fire action potentials at set intervals, connected to surrounding muscle fibers through gap junctions. Cardiac muscle has a sustained depolarization plateau due to calcium entry through voltage-gated calcium channels, resulting in longer contractions. Calcium for cardiac muscle contraction mainly comes from outside the cell.
377 word summary
Cardiac muscle tissue is found only in the heart and is responsible for pumping blood into the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres. However, cardiac muscle fibers are shorter and usually contain only one nucleus. They also have many mitochondria and myoglobin to produce ATP through aerobic metabolism. Cardiac muscle fibers are extensively branched and connected to each other by intercalated discs, which allow for coordinated contractions in a wave-like pattern.
Intercalated discs in cardiac muscle contain two important structures: gap junctions and desmosomes. Gap junctions form channels between adjacent cardiac muscle fibers, allowing depolarizing currents to flow from one cell to the next. This electric coupling enables quick transmission of action potentials and coordinated contraction of the entire heart. Desmosomes anchor the ends of cardiac muscle fibers together, preventing them from pulling apart during contraction.
The contractions of the heart are controlled by specialized pacemaker cells that directly regulate heart rate. These cells respond to signals from the autonomic nervous system and various hormones to speed up or slow down the heart rate. The pacemaker cells are self-excitable and can depolarize to threshold and fire action potentials on their own at set intervals, determining heart rate. They are connected to surrounding muscle fibers and the specialized fibers of the heart's conduction system through gap junctions, allowing for coordinated contraction.
Cardiac muscle has a relatively long action potential with a sustained depolarization plateau. This plateau is produced by calcium entry through voltage-gated calcium channels in the sarcolemma of cardiac muscle fibers. The sustained depolarization and calcium entry result in a longer contraction compared to skeletal muscle. Unlike skeletal muscle, a significant amount of calcium for contraction in cardiac muscle comes from outside the cell rather than from the sarcoplasmic reticulum.
In summary, cardiac muscle tissue is unique to the heart and responsible for pumping blood. It is striated, organized into sarcomeres, and connected by intercalated discs. Gap junctions and desmosomes in the intercalated discs allow for coordinated contractions and anchoring of muscle fibers. Pacemaker cells control heart rate, and the sustained depolarization plateau in cardiac muscle fibers leads to longer contractions. Calcium plays a crucial role in cardiac muscle contraction, with a significant amount coming from outside the cell.