Muscle

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Muscle is the soft tissue found in most animals. Muscle cells contain the filaments of actin and myosin proteins that slide past each other, producing contractions that change both the length and shape of the cell. Muscles work to produce style and movement. They are primarily responsible for maintaining and altering the posture, movement, and movement of internal organs, such as cardiac contraction and movement of food through the digestive system through peristaltic.

The muscle tissue is derived from the mesodermal layers of embryonic germ cells in a process known as myogenesis. There are three types of muscle, skeletal or striated, cardiac, and smooth. Muscle action can be classified as voluntary or unintentional. Smooth and smooth muscles contract without the conscious mind and are called unconscious, while the skeletal muscle contracts by order. Skeletal muscle in turn can be divided into fast and slow twitch fibers.

Muscles are mostly supported by the oxidation of fats and carbohydrates, but anaerobic chemical reactions are also used, especially by fast twitch fibers. This chemical reaction produces an adenosine triphosphate (ATP) molecule used to drive myosin head movements.

The term muscle is derived from the Latin musculus which means "little mouse" may be due to the shape of certain muscles or because the muscle contracts look like a mouse moving under the skin.

Video Muscle

Structure

The muscle anatomy includes a dirty anatomy, which consists of all the muscles of the organism, and the microanatomy, which consists of a single muscle structure.

Type

Muscle tissue is soft tissue, and is one of the four basic types of tissue present in animals. There are three types of muscle tissue recognized in vertebrates:

• Skeletal muscle or "voluntary muscle" is tethered by the tendon (or by aponeurosis in some places) to the bone and is used to affect skeletal movements such as movement and in maintaining posture. Although postural control is generally maintained as a subconscious reflex, the responsible muscles react to conscious control such as non-postural muscle. An average adult male comprises 42% of skeletal muscle and the average female adult is composed of 36% (as a percentage of body mass).
• Fine muscle or "involuntary muscle" is found inside the organ's walls and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels and pili arrector in the skin (where it controls body erections). Unlike skeletal muscles, smooth muscle is not under conscious control.
• Cardiac muscle (myocardium), is also an "unconscious muscle" but is more similar to skeletal muscle structure, and is found only in the heart.

Cardiac and skeletal muscles are "lurik" because they contain sarcaromes packaged in a very regular series of bundles; miofibril smooth muscle cells are not arranged in sarcomas and not striated. While sarcomas in skeletal muscle are arranged regularly, parallel bundles, heart muscle sarcomeres connected to branching, irregular angles (called spinning discs). Striated muscles contract and relax in short, intense bursts, while smooth muscles last longer or even almost permanent contractions.

Skeletal muscle (voluntary) is subdivided into two broad types: slow twitch and quick twitch :

• Type I, slow lag, or "red" muscle, densely packed with capillaries and rich in mitochondria and myoglobin, gives the characteristic red muscle tissue. It can carry more oxygen and retain aerobic activity using fat or carbohydrates as fuel. The slow twitch fibers contract for long periods of time but with little strength.
• Type II, quick twitch muscle, has three major subtypes (IIa, IIx, and IIb) that vary in contractile velocity and the resulting force. Fast twitch fibers contract quickly and strongly but are very tired quickly, retaining only a brief burst of anaerobic activity before muscle contraction becomes painful. They contribute the most to muscle strength and have greater potential for increased mass. Type IIb is the most dense anaerobic, glycolytic, "white" muscle in mitochondria and myoglobin. In small animals (for example, rodents) this is the main rapid muscle type, explaining the pale color of their flesh.

The density of mammalian skeletal muscle tissue is about 1.06 kg/liter. This can be compared with adipose tissue density (fat), ie 0.9196 kg/liter. This makes muscle tissue about 15% denser than fat tissue.

Microanatomy

Skeletal muscle is covered by a layer of hard connective tissue called epimysium. Epimysium anchors muscle tissue to the tendons at each end, where the epimysium becomes thicker and collagen. It also protects the muscles from friction against muscles and other bones. In epimysium is a double collection called fascicula, each containing 10 to 100 or more muscle fibers that are collectively sailed by a perimysium. In addition to encircling each fikel, perimysium is the pathway for the nerves and blood flow in the muscle. Threaded muscle fibers are individual muscle cells (myocytes), and each cell is encased in its own endomisium of collagen fibers. Thus, the entire muscle consists of fibers (cells) that are bundled into the fascicles, which clump together to form muscles. At each bundling level, the collagen membrane surrounds the bundle, and this membrane supports good muscle function by blocking the passive stretch of the tissue and by distributing forces applied to the muscles. Scattered throughout the muscle is a spindle of muscle that provides sensory feedback information to the central nervous system. (This clustering structure is analogous to the neural organization using epineurium, perineurium, and endoneurium).

This same bundle-in-bundle structure is replicated in muscle cells. Inside the muscle cells are myofibrils, which are the bundles of protein filaments. The term "myofibril" should not be confused with "myofiber", which is another name of the muscle cell. Myofibrils are complex strands of several types of protein filaments that are organized together into repeating units called sarkomers. The striated appearance of the skeletal and heart muscles results from the usual pattern of sarcomomes in their cells. Although these two muscle types contain sarcoma, the fibers in the heart muscle are usually branched off to form tissues. The heart muscle fibers are interconnected by the interspersed disk, giving the tissue the appearance of syncytium.

Filaments in sarcomas are made of actin and myosin.

Gross anatomy

The dirty muscle anatomy is the most important indicator of its role in the body. There is an important difference visible between muscular muscles and other muscles. In most muscles, all fibers are oriented in the same direction, running in a line from origin to insertion. However, in muscular muscles, individual fibers are oriented at an angle relative to the action line, attached to the original tendon and insertion at each end. Because the contracting fibers attract at an angle to the overall action of the muscle, the length changes are smaller, but this same orientation allows more fiber (thus more strength) in the given size muscle. Pennate muscles are usually found where changes in length are less important than maximum strength, such as rectus femur.

Skeletal muscle is arranged in discrete muscle, for example is bicep brachii (biceps). The hard and fibrous epimysium of the skeletal muscle is connected and continues with the tendon. In turn, the tendon connects to the periosteum layer that surrounds the bone, allowing the transfer of strength from muscle to bone. Together, this fibrous layer, together with the tendons and ligaments, is a deep fascia of the body.

Muscular system

The muscle system consists of all the muscles present in one body. There are about 650 skeletal muscles in the human body, but the exact amount is difficult to determine. The difficulty lies partly in the fact that different sources group muscles differently and in part because some muscles, such as palmaris longus, are not always present.

Muscle slipping is a narrow muscle length that serves to increase muscle or larger muscles.

The muscular system is one component of the musculoskeletal system, which includes not only the muscles but also the bones, joints, tendons, and other structures that allow movement.

Development

All muscles come from the paraxial mesoderm. The paraxial mesoderm is divided along the length of the embryo into somit, corresponding to the segmentation of the body (most clearly visible in the vertebral column.) Each somite has 3 divisions, sclerotome (which forms vertebrae), dermatome (which forms the skin), and myotome, divided into two parts, epimere and hypomere, which form episial and hypaxal muscles, the only epidermal muscles in humans are the spina erector and the small intervertebral muscle, and are innervated by dorsal flax The spinal cord All other muscles, including limbs, are hypaxia, and is attenuated by the spinal flax of the spinal cord.

During development, myoblasts (muscle progenitor cells) either remain in somit to form muscles associated with vertebral columns or migrate out into the body to form all other muscles. Myoblast migration is preceded by the formation of a connective tissue framework, usually formed from a lateral somatic mesoderm plate. Myoblasts follow chemical signals to the right location, where they join skeletal muscle cells that extend.

Maps Muscle

Physiology

Contraction

The three types of muscles (skeletal, heart and smooth) have significant differences. However, all three use actin motion against myosin to create contractions. In skeletal muscles, contractions are stimulated by electrical impulses transmitted by nerves, motoneuron (motor nerves) in particular. The contraction of the heart and smooth muscle is stimulated by the internal cardiac pacemaker that regularly contracts, and spreads contractions to other muscle cells that it contacts. All skeletal muscle and a lot of smooth muscle contraction is facilitated by the neurotransmitter acetylcholine.

Muscle-generated action is determined by the origin location and insertion. The cross-sectional area of ​​the muscle (not the volume or length) determines the amount of power that can be produced by defining the number of "sarcometers" that can operate in parallel. Each skeletal muscle contains a long unit called myofibrils, and each myofibril is a sarcoma chain. Because contractions occur at the same time for all the sarcomas connected in muscle cells, these sarcoma chains shorten together, shortening the muscle fibers, resulting in a change in overall length. The amount of force applied to the external environment is determined by the mechanics of the lever, in particular the lever-to-lever ratio. For example, moving the bone insertion point further on the radius (farther from the rotational joint) will increase the force generated during flexion (and, as a result, the maximum weight is lifted in this movement), but decrease the maximum flexion rate. Moving the proximal insertion point (closer to the rotation joint) will result in a decrease in strength but an increase in speed. This can be easily seen by comparing the limbs of a mouse to a horse - in the first, the insertion point is positioned to maximize the force (to dig), while at the last, the insertion point is positioned to maximize speed (for running).

Nerve control

Muscle movement

The efferent legs of the peripheral nervous system are responsible for delivering commands to muscles and glands, and are ultimately responsible for voluntary movements. The nerves move the muscles in response to voluntary and autonomous (unconscious) signals from the brain. Deep muscles, shallow muscles, facial muscles and internal muscles all correspond to specific areas of the brain's main motor cortex, directly anterior to the central sulcus that divides the frontal and parietal lobes.

In addition, the muscles react to reflexive nerve stimulation that does not always send signals to the brain. In this case, signals from afferent fibers do not reach the brain, but produce reflexive movements by direct connection with the efferent nerves in the spine. However, most muscle activity is a will, and results from complex interactions between different areas of the brain.

The nerves that control skeletal muscle in mammals relate to groups of neurons along the main motor cortex of the cerebral cortex of the brain. The orders are routed through the basal ganglia and modified by input from the cerebellum before passing through the pyramidal channel to the spinal cord and from there to the motor end plate in the muscle. Along the way, feedback, such as from the extrapyramidal system, contributes signals to affect tone and muscle response.

Deeper muscles such as those involved in posture are often controlled from the nucleus in the brainstem and basal ganglia.

Proprioception

In skeletal muscle, the muscle spindle conveys information about the level of muscle length and stretching to the central nervous system to help maintain posture and joint position. The sense in which our bodies are in space is called proprioception, the perception of body consciousness, the "unconscious" consciousness in which different areas of the body are at one time. Some areas of the brain coordinate motion and position with feedback information obtained from proprioception. The cerebellum and red nucleus typically continuously take the position of the sample against motion and make minor corrections to ensure smooth motion.

Energy consumption

Muscular activity contributes a lot of body energy consumption. All muscle cells produce adenosine triphosphate (ATP) molecules used to drive myosin head movements. Muscles have short-term energy storage in the form of creatine phosphate generated from ATP and can regenerate ATP when necessary with creatine kinase. Muscles also store a form of glucose storage in the form of glycogen. Glycogen can be quickly converted into glucose when energy is required for strong and sustained contractions. In voluntary skeletal muscles, glucose molecules can be metabolized anaerobically in a process called glycolysis that produces two ATPs and two lactic acid molecules in the process (note that under aerobic conditions lactate is not formed, whereas pyruvate is formed and transmitted through the citric acid cycle). Muscle cells also contain fat granules, which are used for energy during aerobic exercise. Aerobic energy systems take longer to generate ATP and achieve peak efficiency, and require more biochemical steps, but produce more ATP than anaerobic glycolysis. Cardiac muscle on the other hand, can easily consume any of three macronutrients (protein, glucose and fat) aerobically without the 'warm up' period and always extract maximum ATP results from each molecule involved. Heart, liver and red blood cells will also consume lactic acid produced and secreted by the skeletal muscle during exercise.

At rest, skeletal muscles consume 54.4 kJ/kg (13.0 kcal/kg) per day. This is greater than adipose (fat) tissue at 18.8 kJ/kg (4.5 kcal/kg), and bone at 9.6 kJ/kg (2.3 kcal/kg).

Efficiency

Human muscle efficiency has been measured (in the context of rowing and cycling) at 18% to 26%. Efficiency is defined as the ratio of mechanical work output to total metabolic cost, as can be calculated from oxygen consumption. This low efficiency is the result of about 40% efficiency generating ATP from food energy, a loss in converting energy from ATP into mechanical work in the muscle, and mechanical losses in the body. The last two losses depend on the type of exercise and the type of muscle fiber used (fast-twitching or slow-twitching). For an overall efficiency of 20 percent, one watt of mechanical power is equivalent to 4.3 kcal per hour. For example, one paddle-caliber manufacturer calibrates its oar ergometer to calculate the burned calories equal to four times the actual mechanical work, plus 300 kcal per hour, this means an efficiency of about 20 percent at 250 watt electricity output. The mechanical energy output of cyclic contraction may depend on many factors, including activation time, muscle strain trajectory, and increased & amp; damage. It can be synthesized experimentally using work loop analysis.

Strength

Muscle is the result of three overlapping factors: physiological strength (muscle size, cross-sectional area, available crossbridging, response to training), neurological strength (how strong or weak the signal which tells the muscles to contract), and mechanical strength (the angle of muscle strength in the lever, the length of the current arm, the combined ability).

Physiological strength

Vertebrate muscles typically produce about 25-33 N (5.6-7.4 lb _f ) of the force per square centimeter of the cross-sectional area of ​​the muscle when isometric and at optimum length. Some invertebrate muscles, such as crab claws, have more sarkomers than vertebrates, resulting in more sites for actin and myosin to bind and thus a much greater force per square centimeter at a much slower speed cost. The forces produced by contractions can be measured non-invasively using either mechanomyography or phonomyography, measured in vivo using a tendon strain (if there is a prominent tendon), or directly measured using a more invasive method.

Certain muscle strengths, in terms of force applied to the bone, depend on length, shortness, cross sectional area, pennation, sarcoma length, myosin isoform, and neural motor unit activation. A significant reduction in muscle strength may indicate an underlying pathology, with graphics on the right being used as a guide.

The "strongest" human muscle

Because three factors affect muscle strength simultaneously and muscles never work individually, it is misleading to compare the strengths in each muscle, and declare that one is the "strongest". But here are some muscles whose strengths are worth noting for many reasons.

• In plain language, muscular "strength" usually refers to the ability to exert power on external objects - for example, lifting weights. By this definition, the masseter or jaw muscle is the strongest. 1992 Guinness Book of Records recorded the achievement of bite strength 4,337 N (975 lb _f ) for 2 sec. What distinguishes the masseter is not something special about the muscle itself, but its advantage in working against the lever arm is much shorter than the other muscles.
• If "strength" refers to the force given by the muscle itself, for example, at the place where it is inserted into the bone, then the strongest muscle is the muscle with the largest cross-sectional area. This is because the tension given by individual skeletal muscle fibers does not vary much. Each fiber can use a force on the order of 0.3 micronewton. By this definition, the body's strongest muscles are usually called quadriceps femoris or maximus gluteus.
• Since muscle strength is determined by the cross-sectional area, the shorter muscles will be stronger "pounds for pounds" (ie, by weight) than the longer muscles of the same cross-sectional area. The lining of the uterine myometrium may be the strongest muscle by weight in the female human body. By the time the baby is born, the entire human uterus weighs about 1.1 kg (40 oz). During labor, the uterus secretes 100 to 400 N (25 to 100 pounds) from the downward force with each contraction.
• The outer muscles of the eyes are very large and strong in relation to the size and weight of small eyeballs. It is often said that they are "the strongest muscle for the job they have to do" and are sometimes claimed to be "100 times stronger than they should be." However, eye movements (especially saccade used on face scanning and reading) do require high-speed movement, and eye muscles are performed every night during fast eye movement sleep.
• The statement that "the tongue is the strongest muscle in the body" often appears in the list of surprising facts, but it is difficult to find any definition of "power" that would make this statement true. Note that the tongue consists of eight muscles, not one.
• The heart has the claim to be the muscle that does the greatest amount of physical work throughout life. Estimated power output ranges from 1 to 5 watts of human heart. This is much smaller than the maximum power output of other muscles; for example, the quadriceps can produce more than 100 watts, but only for a few minutes. The heart does its work continuously for a lifetime without pause, and thus performs "work" of other muscles. The output of one continuous watt for eighty years produces a total work output of two and a half gigajoules.

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Exercise

Exercise is often recommended as a means to improve motor skills, fitness, muscle and bone strength, and joint function. Exercise has several effects on the muscles, connective tissues, bones, and nerves that stimulate muscles. One effect is muscle hypertrophy, an increase in size. It is used in bodybuilding.

Various exercises require the domination of the use of certain muscle fibers on top of the others. Aerobic exercise involves a long and low level of exertion where the muscles are used under the maximum contraction force for long periods (the most classic example is the marathon). Aerobic events, which primarily depend on the aerobic system (with oxygen), use a higher percentage of Type I (or slow-twitch) muscle fibers, consume a mixture of fat, protein and carbohydrates for energy, consume large amounts of oxygen and produce less acid lactate. Anaerobic exercises involve short bursts of high intensity contractions at a much greater percentage of their maximum contraction strength. Examples of anaerobic exercises include sprinting and weight lifting. Anaerobic energy delivery systems using Type II or fast-twitch muscle fibers, mainly dependent on ATP or glucose for fuel, consume relatively little oxygen, protein and fat, produce large amounts of lactic acid and can not survive for a given period. as an aerobic exercise. Many exercises are partly aerobic and partly anaerobic; for example, football and rock climbing involve a combination of both.

The presence of lactic acid has an inhibitory effect on ATP generation in the muscle; although it does not produce fatigue, it can inhibit or even stop performance if the intracellular concentration becomes too high. However, long-term training causes neovascularization within the muscles, improving the ability to move waste products out of the muscles and maintain contractions. After leaving the muscle with high concentrations in the sarcoma, lactic acid can be used by other muscles or tissues as a source of energy, or transported to the liver where it is converted back into pyruvate. In addition to increasing the level of lactic acid, strenuous exercise causes the loss of potassium ions in the muscles and leads to increased concentrations of potassium ions close to the muscle fibers, in the interstitium. Acidification by lactic acid may allow strength restoration so acidosis can protect against fatigue rather than being a cause of fatigue.

Delayed onset of muscle pain is a pain or discomfort that may be felt one to three days after exercise and generally subside two to three days later. After allegedly caused by the formation of lactic acid, a newer theory is that it is caused by small tears in muscle fibers caused by eccentric contractions, or unusual levels of training. Since lactic acid spreads fast enough, it can not explain the pain experienced several days after exercise.

Health

Humans are genetically predisposed to a greater percentage of one type of muscle group above the other. An individual born with a greater percentage of Type I muscle fibers will be theoretically more suited to endurance events, such as triathlon, long-distance running, and long cycling events, while humans born with a greater percentage of Type II muscle fibers will more likely to excel at a sprint event like a 100 meter run.

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Clinical interests

Hypertrophy

Independent strength and performance measures, muscle induced grow larger with a number of factors, including hormone signaling, developmental factors, strength training, and disease. Contrary to popular belief, the amount of muscle fiber can not be increased through exercise. Conversely, muscles grow larger through a combination of muscle cell growth as new protein filaments are added together with the additional mass provided by undifferentiated satellite cells with existing muscle cells.

Biological factors such as age and hormone levels can affect muscle hypertrophy. During puberty in men, hypertrophy occurs at an accelerated rate because the level of growth hormone stimulants produced by the body increases. Natural hypertrophy usually stops at full growth in late adolescence. Since testosterone is one of the major growth hormones of the body, on average, men feel hypertrophy is much more easily attainable than women. Taking additional testosterone or other anabolic steroids will increase muscle hypertrophy.

Muscle, spinal and nerve factors all affect muscle formation. Sometimes a person may see an increase in strength in the given muscle even if only the reverse has been subjected to exercise, such as when the bodybuilder finds his left biceps muscle strong after completing a regimen that focuses only on the right biceps. This phenomenon is called cross-education.

Atrophy

Mammary inactivity and famine causes skeletal muscle atrophy, decreased muscle mass that may be accompanied by fewer numbers and sizes of muscle cells and lower protein content. Muscle atrophy can also result from natural aging or disease.

In humans, prolonged periods of immobilization, such as in cases of rest or astronauts flying in space, are known to cause muscle weakness and atrophy. Atrophy is very attractive to the manned space community, because the weight experienced in space results is the loss of as much as 30% of mass in some muscles. The consequences are also noted in small hibernating mammals such as gold-plated ground squirrels and brown bats.

During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass, known as sarcopenia. The true cause of sarcopenia is unknown, but it may be due to a combination of gradual failure in "satellite cells" that help to regenerate skeletal muscle fibers, and decreased sensitivity to or availability of secreted growth factor are needed to maintain muscle mass and survival of satellite cells. Sarcopenia is a normal aspect of aging, and is actually not a disease state but can be attributed to many injuries in the elderly population as well as decreased quality of life.

There are also many diseases and conditions that cause muscle atrophy. Examples include cancer and AIDS, which induce a body-wasting syndrome called cachexia. Syndrome or other conditions that can cause skeletal muscle atrophy are congestive heart disease and some diseases of the liver.

Disease

Neuromuscular diseases are those that affect muscles and/or their nerve controls. In general, problems with nerve control can cause spasticity or paralysis, depending on the location and nature of the problem. Most neurological disorders, from cerebrovascular accidents (stroke) and Parkinson's disease to Creutzfeldt-Jakob disease, can cause problems with motor movement or coordination.

Symptoms of muscular disease may include weakness, flexibility, myoclonus and myalgia. Diagnostic procedures that may reveal muscular disorders include testing of creatine kinase levels in the blood and electromyography (measuring electrical activity in muscles). In some cases, muscle biopsy may be performed to identify myopathy, as well as genetic testing to identify DNA abnormalities associated with myopathy and specific dystrophy.

Non-invasive elastographic techniques that measure muscle noise are experimenting to provide ways to monitor neuromuscular disease. The sound produced by the muscle derives from the shortening of the filament of actomyosin along the muscle axis. During contraction, the muscle shortens along its longitudinal axis and extends across the transverse axis, producing a vibration on the surface.

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Evolution

The origin of the evolution of muscle cells in metazoans is a highly controversial topic. In one thought scientists believe that muscle cells evolved once and thus all animals with muscle cells had the same ancestor. In other thinking, scientists believe muscle cells evolve more than once and any morphological or structural similarity is due to convergent evolution and genes that precede the evolution of muscles and even mesoderm - the germ layers from which many scientists believe in true muscle cells. earn.

Schmid and Seipel argue that the origin of muscle cells is a monophyletic trait that occurs simultaneously with the development of the digestive and nervous systems of all animals and that this origin can be traced to a metazoan ancestor in which muscle cells are present. They argue that the molecular and morphological similarities between muscle cells in cnidaria and ctenophora are quite similar to bilaterians that there will be an ancestor in the metazoans from which muscle cells originated. In this case, Schmid and Seipel argue that the last ancestors of bilateria, ctenophora, and cnidaria are triploblasts or organisms with three layers of germ and diploblasty, meaning organisms with two layers of germ, evolved secondary to their observations of the lack of mesoderm or muscle which are found in most cnidarian and ctenophores. By comparing the morphology of cnidarians and ctenophores on bilaterians, Schmid and Seipel can conclude that there are myoblast-like structures in tentacles and intestines of several cnidarian species and tentacles of ctenophores. Since this is a unique structure for muscle cells, these scientists are determined based on data collected by their peers that this is a marker for striated muscles similar to those observed on bilateral. The authors also comment that the muscle cells found in cnidaria and ctenophores are often contests because the origin of these muscle cells becomes ectoderm rather than mesoderm or mesendoderm. The origins of true muscle cells are debated by others to be the endoderm part of the mesoderm and endoderm. However, Schmid and Seipel fight this skepticism about whether or not the muscle cells found in ctenophores and cnidaria are true muscle cells by considering that cnidarians progress through the medusa stage and polyp stage. They observed that in the hydrozoan stage medusa there is a layer of cells separated from the distal side of the ectoderm to form striated muscle cells in a manner that looks similar to mesoderm and calls this third separate cell layer ektocodon.. They also argue that not all muscle cells derived from mesendoderm in bilaterian with key examples are that in both the vertebrate eye muscles and spiralian muscles these cells originate from the ectodermal mesoderm rather than the endodermal mesoderm. Furthermore, Schmid and Seipel argue that since myogenesis occurs in cnidarians with the help of molecular regulatory elements found in the specification of muscle cells in bilaterian there is evidence for a single origin for striated muscle.

In contrast to this argument for one origin of muscle cells, Steinmetz et al. argues that molecular markers such as the myosin II protein used to determine the single origin of the striated muscle actually precede the formation of muscle cells. This author uses an example of a contractile element present in a porphera or a sponge that really lacks the striated muscle containing this protein. Furthermore, Steinmetz et al. presents evidence for the origin of polyphyletic muscle cell development through their analysis of morphological and molecular markers present in bilaterians and none in cnidaria, ctenophores, and bilaterian. Steimetz et al. shows that traditional morphological and regulatory markers such as actin, the ability to pair myosin phosphorylation side chains to higher concentrations of calcium concentrations, and other MyHC elements present in all metazoa are not only organisms that have been shown to have muscle. cell. Thus, the use of one of these structural or regulatory elements in determining whether cnidarian muscle cells and ctenophores are quite similar to the muscle cells of bilaterian to confirm a questionable lineage according to Steinmetz et al. Furthermore, Steinmetz et al. explains that the ortholog of the MyHc gene that has been used to hypothesize the origin of the striated muscle occurs through gene duplication events that precede the first true muscle cells (meaning striated muscle), and they show that the MyHc gene is present in a sponge that has contractile elements but no muscle cells correct. Furthermore, Steinmetz et al. Indicates that the localization of this well-duplicated set of genes that function well to facilitate the formation of striated muscle genes and the regulation of cell and gene movements have been separated into myhc and non-myhc muscle. The separation of this set of duplicate genes is demonstrated through the localization of the myhc striated into the contractile vacuoles in the sponge while the more diffusely-diffused myhc muscles are expressed during the development of cell shape and alteration. Steinmetz et al. found a similar pattern of localization in cnidaria with the exception of cnidarian N. vectensis has this striated muscle marker present in smooth muscle of the digestive tract. Thus, Steinmetz et al. argues that the pleitanomorphic nature of orthologes apart from myhc can not be used to determine muscle monophylogeny, and also argues that the presence of striated muscle markers in cnidarian smooth muscle shows a very different mechanism from the development and structure of muscle cells. in cnidaria.

Steinmetz et al. continues to argue for some striated muscle origins in metazoans by explaining that a set of key genes used to form the troponin complex for the regulation and formation of muscle in bilaterians disappears from cnidaria and ctenophores, and of the 47 structural and regulatory proteins observed, Steinmetz et al. can not find even the unique muscle-bound muscle proteins expressed in both cnidaria and bilaterian. Furthermore, Z-discs seem to have evolved differently even in bilaterian and there is an abundance of protein diversity developed even among these clades, indicating a great degree of radiation for muscle cells. Through this distinction from Z-disc, Steimetz et al. argues that there are only four common protein components present in all bilateral muscular ancestors and that this is for the Z-disc components that are required only the actin proteins they have debated as uninformative markers via their pleiomorphic state contained in cnidaria. Through further molecular marker testing, Steinmetz et al. observe that non-bilaterians lack many of the regulatory and structural components necessary for bilaterian muscle formation and do not find a unique set of proteins for both bilaterian and cnidaria and ctenophores that are absent in more primitive animals such as sponges and amoebozoans. Through this analysis, the authors conclude that due to the lack of elements that depend on the bilaterian structure for structure and use, nonbilaterian muscles must originate from different settings with different structural proteins.

In another take on the argument, Andrikou and Arnone used the newly available data on gene regulatory networks to see how the hierarchy of genes and morphogens and other mechanisms of network specifications were distorted and similar between early deuterostomes and protostomas. By understanding not only what genes exist in all the bilaterians but also the time and place of the spread of these genes, Andrikou and Arnone discuss a deeper understanding of the evolution of myogenesis.

In their paper Andrikou and Arnone argue that in order to truly understand the evolution of muscle cells, the function of transcriptional regulators must be understood in the context of other external and internal interactions. Through their analysis, Andrikou and Arnone found that there were orthologists preserved from gene-regulating tissues in both bilateral invertebrates and in cnidaria. They argue that having this common set of general rules allows for high levels of divergence from a functioning network. Andrikou and Arnone found that gene orthologists found in vertebrates have been altered through various types of structural mutations in invertebrate deuterostomas and protostomas, and they suggest that structural changes in these genes allow for significant differences in muscle function and muscle formation. this species. Andrikou and Arnone are able to recognize not only differences due to mutations in genes found in vertebrates and invertebrates but also the integration of specific gene species that can also lead to deviations from the original gene network setting function. Thus, although a general pattern of muscle systems has been determined, they suggest that this could be due to an ancestral gene regulatory network co-opted several times across the lineage with additional genes and mutations that lead to very different muscle development. Thus it appears that the framework of the myogenic pattern may be an ancestral feature. However, Andrikou and Arnone explained that the muscle patterned structure should also be considered in combination with cis regulatory elements present at different times during development. In contrast to the high-level structure of the gene family apparatus, Andrikou and Arnone found that the cis-regulating elements were not well conserved either in time and place in the tissues that could indicate major differences in muscle cell formation. Through this analysis, it seems that myogenic GRNs are GRN ancestors with actual changes in myogenic functions and structures that may be related to gene collaboration at different times and places.

Evolutionarily, the special forms of skeletal and cardiac muscle precede the divergence of the vertebrate/arthropod evolutionary line. This shows that this type of muscle developed in the same ancestor some 700 million years ago (mya). Vertebrate plain muscles have been found to have evolved independently of skeletal and cardiac muscle types.

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See also

• Electroactive polymers - materials that behave like muscles, are used in robotics research
• The power of the hand
• Meat
• Muscle memory
• Myotomy
• Preflexe
• The Law of Rohmert - related to muscle fatigue

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References

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External links

• Media related to muscle in Wikimedia Commons
• University of Dundee article about doing neurological examination (Quadriceps "strongest")
• Muscle efficiency in rowing
• Muscle Physiology and Modeling Scholarpedia Tsianos and Loeb (2013)
• Human Muscle Tutorial (a clear picture of the main human muscle and their Latin name, great for orientation)
• Microscopic stains of skeletal and cardiac muscle fibers to show striation. Notice the different settings of myofibrilar.

Source of the article : Wikipedia