Difference Between Voluntary and Involuntary Muscles

Main Difference – Voluntary vs Involuntary Muscles

Voluntary, involuntary, and cardiac muscles are the three types of muscles found in the animal body. The skeletal muscles are considered as the voluntary muscles whereas smooth muscles are considered as the involuntary muscles. Cardiac muscles are found only in the heart. Voluntary muscles are attached to the skeleton, aiding the movement of parts and locomotion of the animal body. Involuntary muscles are found in the walls of hollow organs, controlling the internal movements of the organs. The internal organs help to passage fluid and food in the digestive system. The main difference between voluntary and involuntary muscles is that voluntary muscles are innervated by the somatic nervous system whereas involuntary muscles are innervated by the autonomic nervous system.

Key Areas Covered

1. What are Voluntary Muscles
      – Definition, Features, Function
2. What are Involuntary Muscles
      – Definition, Features, Function
3. What are the Similarities Between Voluntary and Involuntary Muscles
      – Outline of Common Features
4. What is the Difference Between Voluntary and Involuntary Muscles
      – Comparison of Key Differences

Key Terms: Autonomic Nervous System, Cardiac Muscles, Involuntary Muscles, Skeletal Muscles, Smooth Muscles, Somatic Nervous System, Voluntary Muscles

What are Voluntary Muscles

The voluntary muscles are the type of muscles, which are controlled by the somatic nervous system of the body. Voluntary muscles are also called as skeletal muscles since they are attached to the skeleton and are involved in the movement of body parts and the locomotion. The voluntary muscles are composed of multinucleated, cylindrical cells.

Figure 1: Voluntary Muscle Organization

Each muscle cell is wrapped with a connective tissue called endomysium. The voluntary muscle cells are arranged together in a bundle to form a muscle. Each muscle cell bundle is wrapped with a connective tissue called epimysium. These tissue cell bundles are arranged in compartments called fasciculus. Each fasciculus is wrapped with a connective tissue called perimysium. The voluntary muscle is attached to the skeleton via tendons. The connective tissue layers are involved in providing nourishment and support to the muscle. 

What are Involuntary Muscles

Muscles that act without conscious control are referred to as involuntary muscles. Smooth muscles are considered as the involuntary muscles in the body. Smooth muscles are found in the walls of hollow organs such as the stomach, intestine, urinary bladder, uterus, and the walls of blood capillaries. The involuntary muscles are spindle-like and they comprise a centrally located nucleus. Most of the involuntary muscles contract as a single-unit. The motor neurons of the autonomic nervous system comprise varicosities, a type of neurotransmitter-filled bulges. Since the cells in the involuntary muscles are connected by gap junctions, the neuron signals are transmitted from one cell to the other. Involuntary muscles also exhibit stress-releasing response by which stressed organs release fluids out of the organ. The involuntary muscles are shown in figure 2.

Figure 2: Involuntary Muscle Organization

Similarities Between Voluntary and Involuntary Muscles

• Both voluntary and involuntary muscles are two components of the muscle tissue in the body.
• Both voluntary and involuntary muscles are composed of muscle cells.
• Both voluntary and involuntary muscles are under the control of nervous system

Difference Between Voluntary and Involuntary Muscles

Definition

Voluntary Muscles: Voluntary muscles are the type of muscles that are controlled by the individual’s will.

Involuntary Muscles: Involuntary muscles are the type of muscles that are not under the individual’s will.

Known as

Voluntary Muscles: Voluntary muscles are also known as skeletal muscles.

Involuntary Muscles: Involuntary muscles are also known as smooth muscles.

Found in

Voluntary Muscles: Voluntary muscles are found attached to bones.

Involuntary Muscles: Involuntary muscles are found in the walls of internal organs.

Function

Voluntary Muscles: Voluntary muscles are involved in the movement of body parts and the locomotion of the body.

Involuntary Muscles: Involuntary muscles are involved in the internal movements of the organs, aiding the passage of fluids and food in the digestive system.

Contraction

Voluntary Muscles: Voluntary muscles exhibit fast contractions.

Involuntary Muscles: Involuntary muscles exhibit slow contractions.

Energy Requirement

Voluntary Muscles: Voluntary muscles have a high energy requirement.

Involuntary Muscles: Involuntary muscles have a low energy requirement.

Structure

Voluntary Muscles: Voluntary muscles are long and cylindrical.

Involuntary Muscles: Involuntary muscles are small and spindle-shaped.

Uninucleated/Multinucleated

Voluntary Muscles: Voluntary muscles are multinucleated.

Involuntary Muscles: Involuntary muscles are uninucleated.

Regulation

Voluntary Muscles: Voluntary muscles are under the regulation of the somatic nervous system.

Involuntary Muscles: Involuntary muscles are under the regulation of the autonomic nervous system.

Fatigue

Voluntary Muscles: Voluntary muscles fatigue and need rest at intervals.

Involuntary Muscles: Involuntary muscles do not fatigue and they can work continuously.

Conclusion

Voluntary and involuntary muscles are two components of the muscle tissue of the animal body. The skeletal muscles are considered as voluntary muscles, which are controlled consciously. The skeletal muscles are involved in moving body parts and locomotion. The involuntary muscles are controlled unconsciously and they are involved in the movements of the internal organs. Voluntary muscles are controlled by the somatic nervous system and involuntary muscles are controlled by the autonomic nervous system. This is the main difference between voluntary and involuntary muscles.

Reference:

1. “Muscular Tissue.” Structure and Functions of Human Tissue Types.N.p., n.d. Web. Available here. 08 July 2017. 
2. “STRUCTURE OF SKELETAL MUSCLE.” SEER Training. N.p., n.d. Web. Available here. 07 July 2017.
3. “The Smooth Musculature.” Kenhub. N.p., n.d. Web. Available here. 08 July 2017. 

Image Courtesy:

1. “1007 Muscle Fibes (large)” By OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “1021 Smooth Muscle new” By OpenStax – (CC BY 4.0) via Commons Wikimedia