Types of Muscle Fibres: Muscle fibers consist of a single muscle cell. They help to control the physical forces within the body. When grouped together, they can facilitate organized movement of your limbs and tissues. There are several types of muscle fiber, each with different characteristics.

Types of Muscle Fibres

On the basis of their location, structure and function, there are three types of muscle fibres: skeletal, smooth and cardiac.

Skeletal muscle tissue forms skeletal muscles, which attach to bones or skin and control locomotion and any movement that can be consciously controlled. Because it can be controlled by thought, skeletal muscle is also called voluntary muscle. Skeletal muscles are long and cylindrical in appearance; when viewed under a microscope, skeletal muscle tissue has a striped or striated appearance. The striations are caused by the regular arrangement of contractile proteins (actin and myosin). Actin is a globular contractile protein that interacts with myosin for muscle contraction. Skeletal muscle also has multiple nuclei present in a single cell.

They are attached to skeletal bones. E.g. Biceps
♦ It bears striations in the form of alternate light and dark bands.
♦Muscle fibres are bundled together in a parallel fashion.
♦ A sheath of tough connective tissue encloses several bundles of muscle fibres.
♦The muscle has the ability to contract rapidly and thus is responsible for quick movements.
♦ The muscles are also known as voluntary because their contraction is under the control of will.
♦They get fatigued soon.
♦They are found in the limbs, face, neck and body wall.

Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels. Smooth muscle has no striations, is not under voluntary control, has only one nucleus per cell, is tapered at both ends, and is called involuntary muscle.

Each smooth muscle fiber is spindle-shaped, unbranched and uni-nucleated cell.
♦ The muscle fibers do not show striations.
♦ Cell junctions hold them together and they are bundled together in a connective tissue sheath.
♦ They are known as involuntary muscles as their movement is not controlled by the mind.
♦ Fatigue is rare in smooth muscle fibers.
♦ They are seen in the wall of internal organs such as the blood vessels, stomach and intestine.

Cardiac muscle tissue is only found in the heart, and cardiac contractions pump blood throughout the body and maintain blood pressure. Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle. It has one nucleus per cell, is branched, and is distinguished by the presence of intercalated disks.

They are involuntary muscle seen only in the heart.

♦ Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together.
♦ Communication junctions (intercalated discs) at some fusion points allow cells to contract as a unit, i.e., when one cell receives a signal to contract, other cells also contract.

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By Team Learning Mantras