“Muscles are in a most intimate and peculiar sense the organs of the will. They have built all the roads, cities and machines in the world, written all the books, spoken all the words, and, in fact done everything that man has accomplished with matter.” (Hall, 1906.) The fundamental importance of muscular tissue in human beings is irrefutable as eloquently illustrated by G. Stanley Hall above. Muscle forms the largest group of tissue in the body, comprising of approximately 36% and 10% of body weight in skeletal and smooth muscle respectively. (Sherwood, 2009: 257) Fundamentally, there are a few similarities between skeletal and smooth muscle but these basic similarities aside, skeletal and smooth muscle are highly divergent. Skeletal muscle is striated in appearance, with several levels of muscular organisation providing structure. Functionally, muscle contraction in skeletal muscle occurs with the “sliding filament mechanism”, of which “excitation-contraction coupling” plays a pivotal role. (Sherwood, 2009: 261,264). Conversely, smooth muscle cells are unstriated, with elongated nucleus and arranged in sheets as seen in Figure 1. (Sherwood, 2009: 289) Smooth muscle function is diverse and its uses of Ca2+ ions in “excitation-contraction coupling” unique.
Elongated nucleusDespite so many differences between smooth and muscle cells, an understanding of their similarities will provide insights into muscle’s role in the human body.
Both skeletal and smooth muscle cells consist of thick myosin and thin actin filaments, their cross-bridges are activated by Ca2+ ions and both muscles require adenosine triphosphate (ATP) for activation. (Sherwood, 2009: 290-291) These similarities are fundamental to both types of muscle cells bu...
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...y Bretscher, Hidde Ploegh, Angelika Amon, Matthew P. Scott, Harvey Lodish (2012). Molecular Cell Biology. USA: W.H.Freeman and Co. Ltd.
Hall, G. Stanley (1907). Youth: Its education, regimen, and hygiene. USA: D Appleton and Company. p7-28.
Yawen Ju et al. (2013). Troponin T3 expression in skeletal and smooth muscle is required for growth and postnatal survival: Characterization of Tnnt3tm2a(KOMP)Wtsi mice. Genesis. 51 (9), p667-675.
Hideaki Karaki et al. (1997). Calcium Movements, Distribution, and Functions in Smooth Muscle. Pharmacological Reviews. 49 (2), p157-230.
Carlos M. Moran et al. (2008). Expression of the fast twitch troponin complex, fTnT, fTnI and fTnC, in vascular smooth muscle. Cell Motility and the Cytoskeleton. 65 (8), p652-661.
Lauralee Sherwood (2008). Human Physiology: From Cells to Systems, Seventh Edition. 7th ed. Canada: Brooks/Cole. p257-294.
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
Muscle fibers are cylindrical. They have a diameter around ten to one hundred micrometers and are generally a few centimeters long. Within each muscle cells, contains basal lamina of collagen and glycoproteins. Each fiber contains a structure called excitation-contraction coupling, which is used to make sure the each contractile stimulus is quickly and equally communicated throughout the muscle fiber.
Cain, M. L., Urry, L. A., & Reece, J. B. (2010). Campbell Biology. Benjamin Cummings.
Muscle is a very specialized tissue that has both the ability to contract and the ability to conduct electrical impulses. Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. The muscle may shorten, lengthen or remain the same under tension. Skeletal muscle has an impressive ability to regenerate itself, which it does on a daily basis as well as in response to injury [1].
Repair after a muscle is damaged happens through the division of certain cells who then fuse to existing, undamaged muscle fibers to correct the damage. Different muscle types take different amounts of time to heal and regenerate after it has been damaged. Smooth muscle cells can regenerate with the greatest capacity due to their ability to divide and create many more cells to help out. While cardiac muscle cells hardly regenerate at all due to the lack of specialized cells that aid in repair and regeneration. In skeletal muscle, satellite cells aid in helping restoration after injury. Along with muscles, tendons are very important structures within the human body, and they to can be damaged. However, tendon repair involves fibroblast cells cross-linking collagen fibers that aid in not only reinforcing structural support, but also mechanical support as well (“Understanding Tendon Injury,” 2005). While quite different from muscle repair, tendon repair involves the similarity of reestablishing d...
Although the two main proteins, actin and myosin, that make the contractile nature of muscles are the same, their arrangement coupled with other proteins subsequently causes the overall structure to differ in many respects. The main function is essentially the same in every muscle type, however as the structure varies the function and resulting contraction is different. the way they contraction occurs is different. This shows how structure is adapted to function and vice versa.
Cardiac muscle is a type of involuntary muscle found only in the walls of the heart, specifically the myocardium. Cardiac muscles contract automatically to tighten the walls of the heart in a rhythmic fashion. The heart beats nonstop about 100,000 times each day. Smooth muscle is a type of involuntary muscle found within the walls of blood vessels such as in small arteries and veins. Smooth muscle is also found in the urinary bladder, uterus, male and female reproductive tracts, gastrointestinal tract, and the respiratory tract. Skeletal muscles are voluntarily controlled and are attached to bones by tendons. Skeletal muscles also vary considerably in size and shape. They range from extremely tiny strands such as in the muscle of the middle ear as large like in the muscles of the thigh. The three individual muscle types also serve five main functions. The five basic functions are movement, organ protection, pumping blood, aiding digestion, and ensuring blood flow.
Pocock, G., Richards, C.D. and Richards, D.A. (2013) Human Physiology. 4th ed. Oxford: Oxford University Press.
Studies on muscle typing and its potential to differentiate were widely conducted throughout the last 50 years. It began with publications by Buller et al in 1960 which suggested evidence that the central nervous system controls muscle differentiation. This resulted from the inability of slow muscle differentiation in a cat limb after being operated from the spinal cord. They further postulated that the division and cross-unit of nerves of fast and slow muscles would move the motoneurones that was formerly innervating fast muscle to innervate slow muscle. They then applied this cross-innervation technique to investigate the possible effects in reverse contractile characteristics[1]. It has been documented that chronic electrical stimulation, muscle ablation, hindlimb suspension and hormone manipulation have been used to cause changes in metabolic enzymes, Ca2+ handling proteins , myosin isoforms and regulatory proteins of skeletal muscle and muscle fiber type and size. John Holloszy’s classic paper (1967) provides evidence on the malleability of rat muscles and the adaptation of their energy metabolism to chronic exercise training through simple physiological stimulus. This comes to the two classic papers on hand by Gollnick et al in 1972 and 1973, where they address the idea of fibre type plasticity in human skeletal muscle by using fiber typing and needle biopsy of muscle. The initial interest stemmed from the early work of Reggie Edgerton et al, which provided critical data on the development of fiber type classification systems. Furthermore, Edgerton’s investigation introduced other researchers to the idea of exercise-induced fiber type transformation in rodent muscle.[2] This lead Gollnick and his colle...
In organisms, there are three types of muscle. Smooth muscle helps make up the internal workings of our systems, while cardiac muscle builds our heart, supplying us with oxygen through the blood. The third type of muscle, skeletal, is important for locomotion. It attaches bones to bones, joints to joints, and allows movement. Skeletal muscles differ from one part of the body to another. This is due to the fact that we need to use our bodies for different things. While we may need to move our legs at great length, our fingers might not be able to take the same charge. (National Cancer Institute)
The experiment that tested the contractile level of muscle in various solutions used a muscle fiber from rabbit’s muscle. One fiber was detached, put under microscope, and submerged first under ATP and salt solution (KCl and MgCl2), then ATP only solution, and lastly salt only solution [2]. The fiber’s level of contraction was measured in micrometers. Muscle contractile strength and number motor units employed at various force lev...
of work individual cells can do and also aids in the recovery of muscle cells. Many
The sarcomere is found in structures called myofibrils which make up skeletal muscle fibres. Within the sarcomere there are various different proteins. One of the most significant, myosin is found in the thick filaments of the sarcomere. Although both cells contain myosin, it is important to highlight that smooth muscle cells contain a much lower percentage of myosin compared to skeletal muscle cells. Despite this, myosin filaments in smooth muscle cells bind to actin filaments in a manner similar to that in skeletal muscle cells; although there are some differences. For instance, myosin filaments in smooth muscle cells are saturated with myosin heads so that myosin can glide over bound actin filaments over longer distances, enabling smooth muscle cells to stretch further, whilst in skeleta...
Cardiac muscle is a type of involuntary muscle found only in the walls of the heart, specifically the myocardium. Cardiac muscles contract automatically to tighten the walls of the heart in a rhythmic fashion (pp.212-216). The heart beats nonstop about 100,000 times each day (p.18). Smooth muscle is a type of involuntary muscle found within the walls of blood vessels such as in small arteries and veins. Smooth muscle is also found in the urinary bladder, uterus, male and female reproductive tracts, gastrointestinal tract, and the respiratory tract. Skeletal muscles are voluntarily controlled and are attached to bones by tendons. Skeletal muscles also vary considerably in size and shape. They range from extremely tiny strands such as in the muscle of the middle ear as large like in the muscles of the thigh (Martini, 2000). The three individual muscle types also serve five main functions. The five basic functions are movement, organ protection, pumping blood, aiding digestion, and ensuring blood flow.
Muscle tissues grow by means of physical activity in the same way they are able to become more well-defined (with regards to physical