Difference between Voluntary and Involuntary Muscles

Muscles are a bundle of fibrous tissue in our body which can contract and expand, capable of producing movement in various parts of the body. The muscular system is primarily important for allowing the body to move, maintaining posture, and allowing blood cells to circulate throughout the body. Muscles are generally made up of skeletal muscles, tissue, tendons, and nerves and are related to bones, blood vessels, and other internal organs of our body.

Muscle is a soft tissue that is found in most animals. Muscle cells contain proteins. They are of two types called actin and myosin. These proteins slide past each other which produces a contraction movement. This contraction changes both the length and the shape of the cell. 

When you lift weights or run you need to exert force. This is provided by the muscle. Muscles provide force and help in motion. They are responsible for external motions, postures of sitting or standing, and internal movements like the heartbeat. Also, the food that you take in through your mouth moves down the system. This movement is also done by the muscles and this movement is called peristalsis. Muscles are categorised into three categories depending on their motions and architecture.

What are Voluntary and Involuntary Muscles?

There are three types of muscles called skeletal muscles also called striated muscles, cardiac muscle, and smooth muscle. Another classification of muscles is voluntary and involuntary muscles. The muscles which move without our will are called involuntary muscles. For example, the cardiac muscle in the heart and the smooth muscles are involuntary muscles. The muscles whose function can be controlled are known as voluntary muscles. The skeletal muscles are an example of such voluntary muscle, for example: bending of the hand. 

Voluntary muscle fibres are multinucleated that contain bundles of sarcomeres. These muscles are frequently connected to bones and the skin and are made up of cylindrical fibres. They are primarily controlled by the somatosensory nervous system and play a crucial function in allowing the body to move by contracting and relaxing. Skeletal muscles are among the voluntary muscles.

In the context of cardiac muscle, involuntary muscles are striated and branching. The autonomic nervous system in the body is in charge of controlling the actions of involuntary muscles. Smooth muscles and cardiac muscles are examples of involuntary muscles.

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Differences between Voluntary and Involuntary Muscles

The difference between voluntary and involuntary muscles are summarised in a tabular format.

Skeletal Muscle

It is one of the most common muscle groups that is controlled by the somatic nervous system. It generally refers to a collection of cell bundles and muscle fibres. These muscles play a role in muscle contraction, signalling, and other functions. The skeletal muscles are connected to the bones by tendons. These muscles help in movement or locomotion and help in maintaining body postures. An average male has approximately 42% of skeletal muscle and an average female has about 36%. Skeletal muscles are divided into two types: They are slow-twitch and fast-twitch.

• Slow-twitch muscles are red and are dense with capillaries. They carry more myoglobin and thus have a dark red colour. This muscle can carry more oxygen and can support any aerobic activity for a longer duration. 

• Fast-twitch tissues can contract very fast, but they will get fatigued very soon. They can sustain short bursts of anaerobic activity but soon the muscle contraction becomes painful. They contribute to muscle strength.

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Smooth Muscles 

Smooth muscle is a non-striated, involuntary muscle that lacks sarcomeres and thus no striations.  Smooth muscle is classified into two types: single-unit and multi-unit. The entire bundle or sheet of smooth muscle cells contracts as a syncytium within the single-unit muscle. Single-unit smooth muscle provides slow, consistent contractions that allow substances to flow through the body, such as food in the digestive tract. The multi-unit smooth muscle is made up of cells with few or no gap junctions and so is not electrically connected. As a result, contraction is restricted to the cell that was initially triggered, rather than spreading to other cells. They are found in the internal organs like the oesophagus which is the food pipe, stomach, intestines, urethra and blood arteries. These muscles assist in driving food molecules along the length of the alimentary canal, controlling blood vessel internal diameter, and tightening the uterus during labour and childbirth.

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Cardiac Muscles

Cardiac muscle is found in the heart only and structurally resembles the skeletal muscle. It is an involuntary, striated muscle that makes up the majority of the heart's wall tissue. The myocardium is another name for the heart muscle. It forms a thick middle layer between the pericardium, the outer layer of the heart wall, and the endocardium, with blood supplied by the coronary circulation. Individual cardiac muscle cells are connected by intercalated discs, and the extracellular matrix is made up of collagen fibres and other components. They contain sarcomeres. Sarcomeres are the basic building blocks in muscle tissue. They are packed in regular arrangements and hence resemble striations. Striated muscles contract and relax in short bursts in an intermittent fashion but the smooth muscles can sustain for a prolonged duration of time. 

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We have learnt about the difference between voluntary and involuntary muscles. We also learnt briefly about the different examples of both voluntary and involuntary muscle. To learn more topics of Biology, visit our website.