The difference between voluntary and involuntary muscle is mainly due to their functional property. In a voluntary muscle, the functioning is not automatic control by the somatic nervous system and is in our control. The functioning of an involuntary muscle is automatic which is controlled by the automatic nervous system and not in our control. Voluntary muscle and involuntary muscle are the muscle tissue that involves the functioning of the body and body parts. So, before proceeding to the concept of these two first, we should know about what is muscle and what are its types?
What is muscle?
A muscle is fibrous and dense tissue, which consists of thin and elongated cells refers to “Muscle fibres“. These muscle fibres are the individual cells which are up to 30cm long. The muscle fibres consist of thin filaments or strands which refers to “Myofilaments”.
Types of muscles: Muscles are mainly of two kinds “Voluntary and involuntary”. Voluntary muscle subdivides into skeletal muscle, and involuntary muscle subdivides into smooth and cardiac muscle.
Content: Voluntary Vs Involuntary Muscle
|Properties||Voluntary muscle||Involuntary muscle|
|Alternative name||Striated or skeletal muscle||Smooth or cardiac muscle|
|Nature||It is under one’s desire||It is not under one’s desire|
|Shape||Cylindrical shape||Spindle or cylindrical shape|
|Nucleus||Multinucleated||Uni and bi-nucleated|
|Location||Attached to the bones||Attached to the wall of internal organs|
|Function||Movement of body and body organs||Movement of internal organs|
|Control||By somatic nervous system||By automatic nervous system|
|Muscle contraction||Powerful and rapid||Rhythmic and slow|
|Intercalated disc||Absent||Present in cardiac muscle|
|Examples||Diaphragm, pharynx, abdominal wall etc.||Urogenital, alimentary, respiratory tract etc.|
Definition of Voluntary and Involuntary Muscle
Voluntary muscle: These are the muscles which attach to the bone. The muscle action is in our control when to use them. “Somatic nervous system” controls its functioning and therefore voluntary muscle is ‘Dependent‘. It is of one type that refers to Skeletal muscle which is long, cylindrical muscle fibres.
Involuntary muscle: These are the muscles which attach to the wall of internal organs, and the muscle action is not in our control. “Automatic nervous system” controls its functioning and therefore it is ‘Independent‘. It is of two types, i.e. Smooth and cardiac muscle.
- Smooth muscle: These are small, spindle-shaped muscle fibres.
- Cardiac muscle: These are small, cylindrical and branched muscle fibres.
Before knowing the structural difference, some properties or elements are found in the structure of both voluntary and involuntary muscle that we will first discuss:
Sarcolemma: It envelops the muscle fibre and consist of plasma and basement membrane.
Nucleus: It can be multinucleated or uninucleated. A nucleus is generally oval and flat in shape. Its position can be central or peripheral.
Sarcosomes: There are some other constituents present like enzymes, mitochondria, Golgi body, sarcoplasmic reticulum etc. besides nuclei.
Myofibrils: These are long, thin and thread-like rods, which lies parallel to each other in the muscle fibre. Myofibrils also refer to “Sarcostyles” which plays a vital role in the functioning of muscle contraction and relaxation.
Striations: These are the ridges compose of light or dark bands in the muscle fibres.
Branching: These acts as a bridge that attaches the muscle fibre and gives it a branching appearance.
Now coming onto structural difference, we should also know that the type of voluntary and involuntary muscle. A type of voluntary muscle is skeletal muscle and types of involuntary muscles are smooth and cardiac muscle.
Therefore, skeletal muscle is voluntary in action whereas smooth and cardiac muscle is involuntary in action.
To know the structural difference between voluntary and involuntary muscle, a table is given below:
|Voluntary muscle||Involuntary muscle|
|Properties||Striated muscle||Smooth muscle||Cardiac muscle|
|Shape||Cylindrical with blunt end||Spindle shaped||Cylindrical shape with flat ends|
|Nucleus||Multinucleated||Uninucleated||Uni or bi-nucleated|
|Arrangement||Found in bundle||Found as sheet of visceral organs||Found as continuous network|
|Myofibrils/ Striations||Light and dark bands present||No bands or striations||Bands present|
|Sarcosomes||Numerous||Less in number||Numerous|
|Mode of contraction||Rapid but for short time||Slow but for long time||Slow and rhythmic|
Characteristics features of skeletal muscle
The characteristic structural features of voluntary skeletal muscle are:
- It is long, rod-like and cylindrical in shape.
- Striations present in this, that’s why also refers to “Striated or Striped muscle”.
- Another identifying feature is, it is multinucleated which may be peripheral or central in position.
Characteristics features of smooth & cardiac muscle
The characteristic structural features of involuntary smooth and cardiac muscle are:
- Both smooth and cardiac muscle are small in size whereas the shape of both differs, one is spindle-shaped and the other is cylindrical respectively.
- Striations are absent in smooth muscle whereas present in cardiac muscle.
- Smooth and cardiac muscle are uninucleated and sometimes bi-nucleated which is generally centred in position.
- Another distinct feature is that intercalated disc and branching is present in involuntary cardiac muscle while absent in both smooth and skeletal muscle.
Key Differences Between Voluntary and Involuntary Muscle
- The alternative name of voluntary muscle is skeletal muscle which is under one’s desire. And the alternative name of involuntary muscle is smooth or cardiac muscle which is not under one’s desire.
- The shape and size of voluntary muscle (skeletal) are long and cylindrical in shape whereas the shape and size of involuntary muscle (smooth and cardiac muscle) are small and spindle or cylindrical in shape.
- In a voluntary muscle, branching is absent, and in involuntary muscle, branching is present in cardiac muscle and absent in smooth muscle.
- The skeletal muscle is found attached to the bones whereas involuntary muscle is found attached to the wall of internal organs and helps in body movement and movement of internal organs respectively.
- The somatic nervous system controls the muscle action of skeletal muscle which is dependent whereas the automatic nervous system controls the muscle action of Involuntary muscle which is independent.
- Skeletal muscle shows powerful and rapid muscle contraction but gets fatigued easily whereas involuntary muscle shows rhythmic and slow muscle contraction and don’t get fatigued.
- Sarcomeres and thick sarcolemma are present in a voluntary muscle whereas thin sarcolemma is present while sarcomeres are absent in involuntary muscle.
- An intercalated disc is absent in a skeletal muscle and present in involuntary cardiac muscle.
- The skeletal muscle requires high energy input for the muscle action whereas involuntary muscle requires low energy input for the muscle action.
Both voluntary and involuntary muscle is the muscle tissue in which one is dependent and the other is independent and thus perform different functions like a movement of the body and body organs or muscle contraction and relaxation, gives strength to the body to lift the things.