Question

Which is true of both cardiac and smooth muscle? a. striated b. multinucleated c. involuntary control d. spindle-shaped cells

Short answer

The correct answer is c. involuntary control, as both cardiac and smooth muscle exhibit involuntary control, meaning their contraction and relaxation are not under conscious control.

Step-by-step solution

Eliminate options based on features exclusive to either cardiac or smooth muscle.

Since cardiac muscle is striated, while smooth muscle is non-striated, option (a) cannot be correct. On the other hand, both cardiac and smooth muscle cells contain a single central nucleus, making option (b) incorrect as well.

Identify features that both cardiac and smooth muscle share.

Both cardiac and smooth muscle exhibit involuntary control, i.e., their contraction and relaxation are not under conscious control. This matches with option (c). Option (d) states spindle-shaped cells, which are a characteristic of smooth muscle but not cardiac muscle.

Choose the correct option.

After analyzing the features of both cardiac and smooth muscle, we can conclude that the only true similarity in the given options is involuntary control, which corresponds to option (c). So, the correct answer is: c. involuntary control

Key concepts

Cardiac Muscle

Cardiac muscle is a unique type of muscle found only in the heart. It plays a vital role in pumping blood throughout the body. One of its distinct qualities is its striated appearance, characterized by alternating light and dark bands under a microscope. This striation is similar to skeletal muscle; however, unlike skeletal muscle, cardiac muscle is not under voluntary control.

Its function is regulated by the heart's internal pacemaker system, allowing it to beat rhythmically and continuously without conscious effort. Cardiac muscle cells, known as cardiomyocytes, are typically connected by intercalated discs, which help synchronize heart contractions. This connection ensures efficient blood movement and proper heart function.

• Striated appearance
• Involuntary control
• Presence of intercalated discs

Smooth Muscle

Smooth muscle is quite different from cardiac muscle in both structure and function. It is found in various organs, such as the stomach, intestines, and blood vessels. Unlike cardiac muscle, smooth muscle cells are not striated. Instead, they have a smooth appearance under a microscope, giving them their name. These muscles are responsible for involuntary movements in the body, such as digestion and regulation of blood vessel diameter.

The cells in smooth muscle are spindle-shaped, tapering at both ends, which allows them to fit tightly together in sheets. These cells work in unison to generate movements necessary for bodily functions without conscious control.

• Non-striated appearance
• Spindle-shaped cells
• Found in various organs

Involuntary Muscle Control

Both cardiac and smooth muscles share the feature of involuntary control. This means they operate automatically, without any conscious input from us. Involuntary muscles are essential for maintaining vital functions in the body. In the case of the heart, this means beating to circulate blood. For smooth muscle, it involves peristalsis in the digestive tract and constriction or dilation of blood vessels.

The autonomic nervous system oversees involuntary muscle control, adjusting muscle actions as needed without conscious thought. Our bodies rely on this automatic system to function smoothly, reacting to stress or relaxation and keeping essential processes like digestion and circulation on track.

• Operates without conscious effort
• Controlled by the autonomic nervous system
• Vital for basic physiological processes

Muscle Cell Structure

Understanding muscle cell structure helps in identifying their functions. For instance, both cardiac and smooth muscle cells contain a single, centrally located nucleus, different from the multinucleated structure of skeletal muscle cells.

Additionally, the structural differences between these muscle types contribute to their unique functions. Cardiac muscle cells, with their striated pattern and intercalated discs, facilitate quick and synchronized contractions. Conversely, the smooth, spindle-shaped cells allow smooth muscle to contract slowly and sustain functions over longer periods, like maintaining tension in blood vessels.

• Single nucleus in cardiac and smooth muscle cells
• Distinct cell shapes and structures
• Adaptations support specific muscle functions