Cardiac muscles do not get tetanized because of their unique structure and function.

Explanation:

- Tetanus is a state of sustained muscle contraction that occurs when a muscle is stimulated rapidly and repeatedly without adequate time for relaxation. This phenomenon is caused by the buildup of calcium ions within the muscle fibers.
- Striated unbranched muscles, such as skeletal muscles, can be tetanized because they have a high density of muscle fibers and a well-organized structure that allows for rapid and synchronized contractions.
- Non-striated branched muscles, such as smooth muscles, can also be tetanized to some extent, although their contractions are generally slower and more sustained than those of skeletal muscles.
- Non-striated unbranched muscles, such as those found in the walls of blood vessels, can also be tetanized, but their contractions are typically weaker and more gradual than those of skeletal muscles.
- Cardiac muscles, on the other hand, are unique in their structure and function. They are striated like skeletal muscle, but they are also branched and interconnected like smooth muscle. This allows for coordinated contractions that are more sustained than those of skeletal muscle but less sustained than those of smooth muscle.
- The specialized structure of cardiac muscle fibers also allows for the rapid diffusion of calcium ions, which helps to prevent the buildup of calcium that can lead to tetanus.
- In addition, the cardiac muscle fibers have a built-in refractory period, which prevents them from being stimulated too rapidly and reduces the risk of tetanus.

In summary, cardiac muscles do not get tetanized because of their unique structure and function, which allows for coordinated and sustained contractions without the risk of tetanus.