Category: Biology Second Paper

Muscles whose actions are not controlled by the will of the animal are called involuntary muscles. They are also called visceral muscles because they are present in the walls of various organs (vessels).

It is a long and cylindrical muscle. Its length is 1-4 cm and diameter is 10-40 micrometers. It is also called muscle fiber because the cells look like fine fibers.

1. Sarcolemma: Muscle tissue is covered by a sheath called sarcolemma.
2. Sarcoplasm: Its cytoplasm is called sarcoplasm. Cytoplasm contains mitochondria. Because these cells require a lot of energy.
3. Nucleus: Multiple nuclei in each muscle cell. It performs biological functions of cells.
4. Myofibrils: Myofibril fibers run along the length of the cell. Myofibril fibers are composed of actin and myosin filaments. Actin and myosin filaments together are called sarcomere. Myofibrils have two types of bands. Anisotropic band (A) and isotropic band (I). Darker bands are called anisotropic or A bands and lighter bands are isotropic or I bands.
5. Transverse lines: Several transverse lines are seen in optional muscles. These lines are called linear muscles or marked muscles.
6. Fasciculus: Muscle fibers are arranged in bundles. Each bundle is called a fasciculus. Each fasciculus is covered by perimycium. Many fasciculi join together to form large clusters. Each large cluster is covered by epimycium.

Optional muscle position

Animals have eyes, tongue, pharynx etc.

Optional muscle function/importance/role

1. Human movement is through these muscles.
2. Controls body organs through contraction and expansion.
3. Regulates body posture and muscle tension.
4. Regulates body temperature.

1. Human movement is through these muscles.
2. Controls body organs through contraction and expansion.
3. Regulates body posture and muscle tension.
4. Regulates body temperature.

Animals have eyes, tongue, pharynx etc.

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It is a long and cylindrical muscle. Its length is 1-4 cm and diameter is 10-40 micrometers. It is also called muscle fiber because the cells look like fine fibers.

1. Sarcolemma: Muscle tissue is covered by a sheath called sarcolemma.
2. Sarcoplasm: Its cytoplasm is called sarcoplasm. Cytoplasm contains mitochondria. Because these cells require a lot of energy.
3. Nucleus: Multiple nuclei in each muscle cell. It performs biological functions of cells.
4. Myofibrils: Myofibril fibers run along the length of the cell. Myofibril fibers are composed of actin and myosin filaments. Actin and myosin filaments together are called sarcomere. Myofibrils have two types of bands. Anisotropic band (A) and isotropic band (I). Darker bands are called anisotropic or A bands and lighter bands are isotropic or I bands.
5. Transverse lines: Several transverse lines are seen in optional muscles. These lines are called linear muscles or marked muscles.
6. Fasciculus: Muscle fibers are arranged in bundles. Each bundle is called a fasciculus. Each fasciculus is covered by perimycium. Many fasciculi join together to form large clusters. Each large cluster is covered by epimycium.

Muscles whose functions are controlled by the will of the animal are called voluntary muscles. It is also called skeletal or linear or smooth or striated muscle. There are 656 voluntary muscles in the human body.

Muscles are divided into three groups based on function, location and structure. These are-

1. Optional or linear or smooth or skeletal muscle.
2. Involuntary or nonlinear or smooth or visceral muscle.
3. Heart muscle or cardiac muscle.

Muscle tissue, which is formed from embryonic mesoderm, is capable of contraction and expansion and is composed of numerous fibers. Muscles are formed by the process of myogenesis. 40% of total body weight is muscle. Its cells are long and narrow, known as fibers.