Skeletal Muscle

Skeletal Muscle Structure.The cells of skeletal muscles are long fiber-like structures. They contain many nuclei and are subdivided into smaller structures called myofibrils. Myofibrils are composed of 2 kinds of myofilaments. The thin filaments are made of 2 strands of the protein actin and one strand of a regulatory protein coiled together. The thick filaments are staggered arrays of myosin molecules.

types of muscle tissues : skeletal, cardiac, smooth. Each of these different tissues has the ability

There are three main types of muscle tissue in the body: Skeletal muscle, smooth muscle and cardiac muscle. Firstly, skeletal muscle has a stripped appearance when it is examined under a microscope so it is sometimes known as striated/stripped muscle. Skeletal muscle is voluntary and this means that it is under conscious control. Secondly, there is smooth muscle which is an involuntary muscle that operates without any conscious control. This muscle is controlled by the nervous system. Smooth muscle can be found in the blood vessels and the walls of the digestive system and it helps to control digestion and blood pressure. Lastly, there is cardiac muscle which is located in in the wall of the heart. Cardiac muscle is involuntary and this means that it is not under conscious control. This is made up of a specialised type of tissue which is striated and it has its own blood supply. The contractions aid the pumping of blood through the blood vessels

Rationale, Significance and Hypothesis. An extrinsic factor, which exerts a dominant influence on skeletal muscle fiber phenotype, is the nervous system. Buller et al. (1960) elegantly demonstrated the plastic nature of skeletal muscle fibers in response to changes in innervation type. Later, Lφmo and Westgaard (Lφmo and Westgaard, 1974; Westgaard and Lφmo, 1988) demonstrated that depolarization of muscle with specific patterns and frequencies of electrical activity are sufficient to cause changes in mature muscle fiber phenotypes. However, how myofibrillar gene expression and structural organization is affected by the frequency of impulses during activity, the amount of activity over time, or other characteristics of patterned activity is essentially unknown. To answer these questions will require the isolation and study of subsets of muscle-specific proteins in relation to different electrical activation patterns in vivo, an issue that cannot be easily addressed in preparations currently used in the study of muscle development and maintenance. However, using novel in vivo approaches can, in part, circumvent this difficulty.

Martini, F. H., Nath, J. L., and Bartholomew, E. F. “Muscle Tissue.” Anatomy & Physiology. 9th

Myofibrils are made up of long proteins that include myosin, titin, and actin while other proteins bind them together. These proteins are arranged into thin and thick filaments that are repetitive along the myofibril in sectors known as sarcomeres. The sliding of actin and myosin filaments along each other is when the muscle is contracting. Dark A-bands and light I-bands reappear along myofibrils. The alignment of myofibrils causes an appearance of the cell to look banded or striated. A myofibril is made up of lots of sarcomeres. As the sarcomeres contract individually the muscle cells and myofibrils shorten in length. The longitudinal section of skeletal muscle exhibits a unique pattern of alternating light and dark bands. The dark staining, A-bands possess a pale region in the middle called the H-zone. In the middle of the H-zone the M-line is found, that displays filamentous structures that can join the thick filaments. The light-staining bands also known as I-bands are divided by thin Z-line. These striated patterns appear because of the presence of myofibrils in the sarcoplasm (IUPUI, 2016).

There are the Smooth, the Skeletal, and the Cardiac muscular tissues. Smooth muscles are made of spindle-shaped cells.

Muscles owe their ability to contract to structural units called sarcomeres, and a single muscle fiber can contain many thousands of these structures, aligned one next to the other. Each mature sarcomere is made up of precisely arranged and intertwined thin filaments of actin and thicker bundles of motor proteins, surrounded by other proteins. Sliding the motors along the filaments provides the force needed to contract the muscle. However, it was far from clear how sarcomeres, especially the arrays of thin-filaments, are assembled from scratch in developing muscles.

The muscle fibers are multinucleated (contain many nuclei), have band-like striations, and contraction is by conscious control. Cardiac muscle Cardiac muscle is located in the walls of the heart and is classified as cardiac, striated, involuntary muscle. The muscle fibers are branched, contain a single nucleus, have band-like striations, and are not under conscious control. They have thicker striations, called intercalated discs, where one muscle fiber joins the next fiber.

There are proteins other than myosin in the thick filaments of are muscle species. Hu, et. al.

The solid framework is the body's system of tissues that controls development both of the body and inside it, (for example, the heart's pumping activity and the development of nourishment through the gut). Development is created through the constriction and unwinding of particular muscles.

the skeletal muscle pump- in the limbs, the veins are surrounded and massaged by the muscles. Contracting muscles squeeze the blood out of the compressed part of a veinwin and the valves ensure that this blood can only go toward the heart.

One of the ways that the myostatin gene regulates the amount of muscle fibers produced is through the cell cycle. Myoblasts build up in the G0, G1 and G2 phase of the cell cycle

A muscle is made up of individual cylindrical muscle cell which are called muscle fibers, which are surrounded by connective tissue called endomysium. Each one of these endomysium enclosed fibers are bundled together and surrounded by more connective tissue called a fasciculus. In turn, these collection of muscle fibres called fascicles are bundled together again, and are surrounded by further connective tissue called perimysium. These perimysium encased bundles are once again further surrounded by more connective tissue called the epimysium. It is portions of this epimysium that

form of myosin ATP and are not very good at delivering calcium to the muscle