• Muscles are made up of highly specialized thin and elongated cells called muscle fibres. The muscle fibres contains specialized cytoplasm called sarcoplasm that contain network of the membrane called sarcoplasmic reticulum. The muscle fibres may be bounded by the cell membrane called sarcolemma. Each muscle fibre may contain numerous longitudinal fibrils called myofibrils.

Basic physiological property of muscle tissue

1. Contractibility
2. Excitability
3. Extensibility
4. Elasticity

Types of muscle

1. skeletal muscle
2. smooth muscle
3. cardiac muscle

1. Skeletal muscle:

• It acquires its name because most of the muscles involved are attached to skeleton, and make it move.
• Also known as Striated muscle -because it cell (fibre) are composed of alternating light and dark band (stripe).
• Also known as voluntary muscle

Structure-

• Composed of muscle fibres. Each muscle fibre is long, cylindrical shaped with numerous nuclei.
• Each fibre is 1.2 inch long and 0.004 inch in diameter ( longest fibre-Sartorius muscle;12 inch, shortest fibre- stapedius muscle;0.04 inch)
• Each fibre contains numerious myofibrils, which are made up of thick and thin threads called
• Thick myofilament is composed of larger protein-
• Thin myofilament is composed of smaller protein- actin
• When viewed with light microscope, skeletal tissue shows a pattern of alternating light and dark bands. The bands are caused by th earrangement of actin and myosin myofilament in the muscle fibre.
• An overlapping of thick myosin and actin myofilaments produce- dark A band (anisotropic band);doesnot allow light to pass
• Thin actin myofilament alone produce- light I band(isotropic band);allow light to pass.
• Cutting across each I band is a dark Z line
• Within A band is a somewhat light H zone( Hensen’s disc), which consists only myosin myofilament
• The area between two Z line is known as sarcomere, which is the fundamental contractile unit of myofibril

Functions: Voluntary in functions. They bring about the movement of the organs and locomotion of the body

• Skeletal muscles undergo powerful and rapid contractions with short rest periods and hence get fatigued easily.
• They are supplied by voluntary Nervous system (CNS and PNS).
• They require large amount of energy, so are supplied with blood vesssels and numerous elongated mitochondria and glycogen granules.
• Found- attached to head, trunk, limbs, also in body wall, tongue, pharynx, oesophagus

2. Smooth muscle:

• It get its name because it is not striated, and appear smooth under microscope.
• Also called involuntary muscle because it is controlled by ANS

Structure

• Muscle fibre is long (but not nearly as long as skeletal muscle fibre),spindle shaped and slender. Contain only one nucleus, situated at the centre of the fibre at the broadest part
• Smooth muscle fibre is enclosed by sarcolemma, and contain numerous longitudinal myofibrils
• Actin and myosin myofilaments within myofibrils are very thin and are arranged more randomly than in skeletal muscle, so there is no stripes.
• 2 main characterstics
• Its contraction and relaxation period are slower
• Its action is rhythemical. Its contraction may last for 3o sec or more, but it doesnot tired easily. Such sustained contraction puls the ability to stretch made it suitable to muscular control of stomach, intestine, urinary bladder, uterus

3. Cardiac muscle:

• It is present only in heart

Structure-

• Under microscope, they have similar striation as skeletal muscle
• Cardiac muscle cells are closely packed but each cell are nucleated and separated from each other
• The cells are joined end to end by the specialised cell junctions called intercalated disks that attach one cell to another with desmosomes, connect the myofibril filaments of adjacent cells and contain gap junctions that help to syncronise the contraction of cardiac muscle, by allowing impulse transmission from one cell to another.
• They contain light I and dark A band, the intercalated disk always occur at the location of Z-line
• Supplied with central and autonomous nervous system
• The rhythmic contraction on its own
• They don’t get fatigue, so called as fatigue less muscle.

Muscular tissue: skeletal, smooth and cardiac muscle

The post Muscular tissue: skeletal, smooth and cardiac muscle appeared first on Online Biology Notes.

Muscle

• The word muscle is derived from Latin word “musculus” which means little mouse.  It is named so because of the movement of muscle under the skin resembles a running mouse.  Joints make a skeleton potentially movable and bones provides a basic system of levers but bones and joints cannot move by themselves. The driving force behind the movement is the muscle.

There are three types of muscles

1. Smooth muscle
2. Cardiac muscle
3. Skeletal muscle

1. Skeletal muscle

• Skeletal muscle is attached to bone and helps in movement. It is also known as striated muscle because the muscle fibers shows alternate dark and light band under light microscope. Muscle are usually in a partial contracted state which give muscle tone and make ready for contraction under the stimulus preceding a complete contraction.

Figure: Skeletal muscle fibre

Gross structure:

• Muscle is composed of muscle cell, which are called as muscle fibres because they are so long, cylindrical shape multi nucleated cell more resemble to fibre than cell. They are arranged parallel to each other.
• Each fibre is multimucleated and the nucleus are located near the surface of each fibre.
• Bundle of fibres are surrounded by collagen fibres and connective tissues.
• Each muscle fibres is enclosed by a plasmamembrane called Sarcolemma.
• The cytoplasm is known as sarcoplasm which contain large number of mitochondria.

Ultra structure:

• Muscle fibre is composed of large number of myofibril arranged parallel to each other. Around each myofibril, a network of sarcoplasmic reticulum runs parallel forming transverse tubules (T-tubules).
• Close examination of myofibril shows it is composed of two types of longitudinal filaments.
• Thin filament is made up of actin protein whereas thick filament is made up of myosin protein.
• These myofilament are arrange in such as a way that they form alternate dark and light band.
• The dark band is formed where actin and myosin interlocked each other, called A-band. The light band between the A-band formed by actin only known as I-band.
• Cutting across I-band is Z-line.
• Within an A-band there is somewhat lighter H-zone which contain only myosin.
• Extending across H-zone there is a delicate M-line, which connects adjacent myosin filament.

The distance between Two Z-line represents a fundamental unit for muscle contraction known as Sarcomere.

Muscle-Skeletal Muscle-Gross and Ultra Structure

The post Muscle-Skeletal Muscle-Gross and Ultra Structure appeared first on Online Biology Notes.