Check all those that are characteristic of cardiac muscle:
Cells are striated.
Cells are structurally and functionally separated from one another.
Gap junctions join adjacent cells.
Requires external stimulation to produce a contraction.
The correct answer and explanation is :
The correct characteristics of cardiac muscle are:
✅ Cells are striated.
✅ Gap junctions join adjacent cells.
The incorrect characteristics are:
❌ Cells are structurally and functionally separated from one another.
❌ Requires external stimulation to produce a contraction.
Explanation:
Cardiac muscle is a specialized type of muscle found exclusively in the heart. It shares some characteristics with both skeletal and smooth muscle but has unique properties that allow it to function efficiently.
- Cells are striated (✅ True)
Cardiac muscle cells contain sarcomeres, the structural units responsible for contraction. These sarcomeres are arranged in a repeating pattern, giving cardiac muscle its striated appearance, similar to skeletal muscle. - Gap junctions join adjacent cells (✅ True)
Cardiac muscle fibers are connected by intercalated discs, which contain gap junctions and desmosomes. Gap junctions allow ions and electrical impulses to pass directly from one cardiac cell to another, ensuring rapid and synchronized contraction of the heart. Desmosomes provide mechanical strength to withstand the continuous pumping of the heart. - Cells are structurally and functionally separated from one another (❌ False)
Unlike skeletal muscle, where individual fibers are independent, cardiac muscle cells are electrically and functionally connected through intercalated discs. This allows the heart to contract as a coordinated unit rather than as isolated cells. - Requires external stimulation to produce a contraction (❌ False)
Cardiac muscle is myogenic, meaning it can generate its own electrical impulses without requiring external stimulation from the nervous system. The sinoatrial (SA) node, the heart’s natural pacemaker, initiates each heartbeat autonomously. While the autonomic nervous system can modify heart rate, it does not directly cause the heart to contract.
These characteristics make cardiac muscle highly efficient for continuous, rhythmic contractions throughout life.