What are Muscles?
Muscles are soft tissues. Muscle cells consist of actin and myosin. Actin is a family of globular multi-functional proteins whereas, myosin is a superfamily of motor proteins. The role of actin is to produce microfilaments. On the other side, myosin is best known for muscle contraction. They help in changing the shape and length of muscle cells.
Muscles are responsible for the changes in posture and movements of internal organs, such as digestive systems, heart contraction. More than 700 are present in the organ systems i.e 40% of the bodyweight is made up of muscles.
There are three types of muscles based on structure and movements; Skeletal muscles, smooth muscles, and cardiac muscles. Based on their control mechanism they are further divided into voluntary and involuntary muscles.
Difference between Voluntary and Involuntary Muscles
|Sr No.||Character||Voluntary Muscles||Involuntary Muscles|
|1.||Contraction||The contraction is under control of the Central nervous system.||The contraction is under the control of the Autonomic nervous system.|
|2.||Type of contraction||In the voluntary muscles, contraction is always fast and powerful.||In the involuntary muscles, the contraction is always slow.|
|3.||Energy||The requirement for energy is high.||The requirement of energy is low.|
|4.||Type of cell||The cells are multinucleated.||The cells are uninucleated.|
|5.||Shape||The shape of these muscles is long, cylindrical.||The shape of these muscles is small, spindle-shaped.|
|6.||Nucleus||The nucleus is present at the periphery.||The nucleus is present at the center.|
|7.||Functions||Voluntary muscles can be controlled under command.||Involuntary muscles cannot be controlled under command.|
|8.||Rest period||They get fatigued and need rest at regular intervals.||They do not get fatigued easily and can work continuously.|
|9.||Sarcolemma||The sarcolemma is thick.||The sarcolemma is thin.|
|10.||Found in||They are present in the organs like tongue, middle ear muscles, attached to the bones.||They are present in the organs like alimentary tracts, respiratory tracts, blood vessels, ducts of glands.|
Voluntary muscles are the muscles used by an individual to move and use under conscious control. Skeletal muscles are the voluntary muscles, as they can be controlled under command. Skeletal muscles are further divided into fast-twitch (high force, rapidly fatiguing) and slow-twitch (low force, slowly fatiguing) fibers.
These muscles are responsible for the movement of parts. Regular exercise will help to improve the strength of voluntary muscles. These muscles are connected by tendons to the bones and are used to maintain posture and locomotion. An average adult male body consists of 42% voluntary muscles whereas the average female body consists of 36%.
The two types of skeletal muscles are slow-twitch and fast-twitch.
Slow-twitch fiber gives the red characteristic to the muscle tissue. These muscles are red and dense with capillaries. They are rich in mitochondria and myoglobin too. Myoglobin is an iron and oxygen-binding protein present in skeletal muscles. This excessive presence of myoglobin results in red colour.
Slow-twitch muscles carry oxygen using fats or carbohydrates as fuel and support any aerobic activity for long. These muscles do not get fatigued easily and work for a long duration continuously. The contraction is for a long duration but they use little force.
Fast-twitch fibers contract very fast uses high energy. These muscles fatigue easily and work for a short duration. They help to improve the strength of muscles. Short anaerobic activities can be performed as it tires very fast.
Involuntary muscles are the muscles controlled by the automatic nervous system and are never affected by voluntary nerve activities. These muscles are present in the organs and structures such as the stomach, intestines, bladder, bronchi, blood vessels, arrector pili (skin hair erection controller).
Unlike voluntary muscles, these muscles act without conscious control in the human body and cannot be controlled willingly. Involuntary muscles are also known as smooth muscles. Muscles found in the heart, digestive system, respiratory system works automatically.
An Intercalated disc is absent in both these muscles. This disc is found in Cardiac muscle.
Cardiac muscles are unique and are found only in the heart. These muscles maintain proper blood circulation. These muscles are striated and contain sarcomeres. These sarcomeres are packed into arrangements of bundles. On the other side, myofibrils of smooth muscle cells are not striated as their sarcomeres are not arranged. Striated muscles contract and relax in a short duration of time.
We discussed different muscles and their important functions also. Not only the movements but muscle systems are also important to protect the body from external shock. Thus these muscles are important for the human body in many factors.