Difference Between Voluntary and Involuntary Muscles

The muscular system of the human body is very important in movement, maintaining proper body shape and posture and regulating temperature. Scientific researches show that a normal human body consists of about 650 various muscles and the majority of them are attached to skeletal bones. Based on movement and structure, these muscles are divided into three major types, i.e. smooth muscles, cardiac muscles and skeletal muscles. However, all the muscles in our body can either be controlled by us consciously, or work on their own, without active commands. As a result, the three main categories of muscles are put into two main categories; voluntary muscles and involuntary muscles – depending on their control mechanisms.

Muscles which are under an individual’s control, biceps for instance, are known as “voluntary muscles”, while muscles, such as the cardiac muscle, which are not actively controlled by the individual, are known as “involuntary muscles”.

Voluntary muscles are linked with the somatic nervous system, which helps us move our legs and arms according to our requirements and will. Involuntary muscles, on the other hand, are connected with with the autonomic nervous system.

Voluntary muscles can contract and relax quickly and vigorously, but involuntary muscles are usually deliberate and rhythmic in their movements.

Skeletal muscles are considered as voluntary muscles, while cardiac and smooth muscles are treated as involuntary muscles.

Voluntary muscles constitute a major percentage of the total body weight, whereas involuntary muscles contribute the remaining.

Voluntary muscles are always attached to the skeletal system (bones), whereas involuntary muscles are visceral.

Involuntary muscles are made up of spindle-shaped fibers, while voluntary muscles are made up of barrel-shaped (cylindrical) fibers.

Voluntary muscles are un-branched while involuntary muscles are branched, forming proper networks.

Intercalated disc is missing in voluntary muscles, but it is present in involuntary muscles.


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    Voluntary Muscles

    Muscles that are under conscious control are called voluntary muscles. They consist of bundles of striated fibers and move according to the instructions of the brain. For example, the muscles of arms, legs and neck etc are voluntary muscles, as they move when we want them to move. Usually these types of muscles are known as skeletal muscles as they are attached to the bones of the skeletal system.

    Image Courtesy: wellnessadvocate.com

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    Involuntary Muscles

    Muscles that an individual cannot control are called involuntary muscles. They are also known as smooth and cardiac muscles. The heart, esophagus, iris and intestine etc are great examples of involuntary muscles as they work on their own.

    Image Courtesy: factmonster.com 

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