Muscle And Smooth Muscle

Contractility of ASM requires an increased levels of intracellular Ca2+. When surface receptors are not activated, Ca2+ levels are low. Upon activation of these cell surface receptors by contractile agonists e.g. acetylcholine, serotonin and histamine, intracellular Ca2+ increases causing a contraction (9). Smooth muscle cell contraction is controlled by both receptor and mechanical activation of proteins actin and myosin and also changes to membrane potential.

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.

Smooth muscle is one of three muscle fiber types found in animals. Unlike skeletal and cardiac muscle cells, smooth muscle cells are not striated, and have single nuclei. Smooth muscles are typically under control of the autonomic nervous system, and do not contract voluntarily. Smooth muscle contracts slowly,

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

Smooth muscle contraction occurs when calcium is present in the smooth muscle cell and binds onto calmodulin to activate myosin light chain kinase (Wilson et al., 2002). Phosphorylation of myosin light chains result in myosin ATPase activity thus cross-bridge cycling occurs causing the muscle to contract (Horowitz et al., 1996). There are two known models of excitation and contraction in smooth muscle, electromechanical coupling (EMC) and pharmomechanical coupling

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

These muscle tissue cells specialised to contract and move parts of the body. It is also capable of responding to stimuli. There are three types of muscle in the body such as: skeletal, cardiac and smooth. Each muscle is created of muscle fibers that are capable of contracting and returning back to original state-relaxation. Contraction causes movement of the skeleton, soft tissue, blood or specific material. Skeletal muscle is attached to the bones of the skeleton. Some facial muscles are attached to the skin. They have direct control over them through nervous impulses from our brain sending messages to the muscle. Contractions can vary to produce fast, powerful movements. These muscles also have the ability to stretch and contract to return to original shape. Cardiac muscles are found in the chambers of the heart such as the atria and ventricles. It is under the control of the automatic nervous system; however, even without nervous input contractions can occur. It is completely different to all the other muscles. Smooth muscles are also known as involuntary due to our inability to control its movement. This muscle is usually found in the walls of hollow organs

Muscle fibres, as shown in Diagram 1, consist of myofibrils, which contain the proteins, actin and myosin, in specific arrangements . The diagram illustrates how a muscle is made up of many fascicles, which in turn are made up of many endomysiums, and within them, many muscle fibres. Each muscle fibre is made up of many myofibrils that consist of sarcomeres bound end on end . Actin is a thin filament, about 7nm in diameter, and myosin is a thick filament, about 15nm in diameter , both of which reside in the sarcomere. They are held together by transverse bands known as Z lines . Diagram 2 shows actin and myosin filaments within a sarcomere, and the Z lines that connect them.

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.

A) CURRENT STATE OF KNOWLEDGE Vascular smooth muscle cells (VSMC) and extracellular matrix (ECM): Blood vessels, include arteries that transport blood from the heart to the systemic circulation, and veins that transport blood back again into the heart. A remarkable change in blood vessel structure and function happened, with the emergence of a high-pressure, pulsatile circulatory system in vertebrates. Blood vessels then evolved from simple tubes for channeling blood or other body fluids from a low-pressure heart. According to their sizes and structures, arteries can be subdivided into four categories: large elastic arteries, medium-sized muscular arteries, small arteries (s Law, the larger the aortic diameter, the larger the wall tension

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

Immunohistochemical analysis for smooth muscle actin (SMA) was done and the intensity of staining and staining location were considered.

Both of these muscles expand and contract as they have complex structures so it is essential how they do this. The cardiac muscle needs the contractions to occur in order to pump blood out of the atria and into the ventricles and round the circulatory system so the structure of this muscle shows the systole of the heart. The contractions of the skeletal muscle also depend on its structure. The binding and releasing of two strands of sarcomere is how the repeated pattern of contractions occurs. ATP is used to prepare myosin for binding to allow the contractions to happen. The skeletal and cardiac muscle also both has elasticity. The elasticity is used to restore the muscles back to their original lengths which enable them to resume back to their original length once they have contracted and been stretched.