General Information About Muscles
Muscles are the active elements of the movement system. The kinetic force required to create the movement occurs in the muscles. The source of the force is the substances that we take as food and which, after undergoing many changes in the alimentary organs, mix with the blood and come to the muscle cells through the circulatory organs. The potential energy hidden in these materials is converted into kinetic energy during the events that occur in the muscle cells. As with all motors (contact), a stimulus is needed in order for the muscles that generate kinetic energy like a motor to be activated. This excitation can also be in the form of mechanical, chemical or electrical current. We can activate the muscles with a blow to the muscle, the effect of some chemical substances or an electric current. However, the movements caused by such external stimuli are not normal and physiological. The excitations that create the normal movements of the muscles in all living things come from the nerve cells in the brain or spinal cord.
Muscles work, if one or both of the attachment points are mobile, the change in shape is manifested by shortening, thickening and hardening. If both ends of the muscle remain stationary under the action of other forces, the muscle does not shorten, but becomes stiff. In such cases, the muscle cannot produce any movement. However, the muscle still works, creates a certain force, and this force is used to oppose another force. For example, in order to hold a weight in our hands at a certain height, our arm and forearm muscles must work and create a force that can withstand the weight, even though we are not making any movement at that moment. As a second example, we can show that a part of our body is fixed by the muscles in a given situation. Meanwhile, the muscles involved in this work work, but they do not shorten, do not change their shape, and do not activate the organ they have detected.
The shortening, thickening and hardening of the muscles and their activation of the organs they attach to are possible thanks to the specific qualities of the muscle cells called contractility (shortening ability).
Muscle tissue; The structure of muscle cells is adjusted to the function of the cell, and various elements of the cell are in a position to change their shape and state during contraction. Let us now briefly review the various muscle tissues seen in the human body.
In terms of microscopic structure, we can divide the muscles seen in the human body into three groups as smooth muscles, striated skeletal muscles and cardiac muscles. Just as in terms of microscopic structure, these three types of muscles differ from each other in terms of function. Smooth muscles and striated heart muscles are not subject to our will and are controlled by the autonomic nervous system. The work of the striated skeletal muscles is subject to our will and is governed by the cerebro spinal nervous system.
The work of the striated muscles managed by the cerebro spinal system can occur reflexively for a long time without our knowledge. On the other hand, cortical centers have a great influence on the functioning of some smooth muscles governed by the autonomic nervous system. Here, after briefly reviewing the structure and properties of smooth muscle fibers, we will examine the main striated skeletal muscles. Striated cardiac muscles will be mentioned when describing the cardiovascular system.
Smooth muscle fibers are mostly found in the walls of our internal organs and vessels. However, there are also smooth muscle fibers that are involved in the ligaments that connect our various organs and in various parts of various organs. Smooth muscle fibers contract slowly and can pause in any phase of the contraction and maintain the shape and state they have taken at that moment for a long time without consuming much energy and without getting too tired. Therefore, smooth muscle fibers are usually found in organs that cause slow movements, but where the state of these movements must be maintained for a long time.
Smooth muscle fibers are spindle-shaped, up to 0.5 mm. They are cells up to 3 – 4 microns in length, pale in color and mononuclear. The nucleus is oval in shape and located in the middle of the cell. In the sarcoplasm, there are very thin fibrils (miofibrils) parallel to each other and to the length of the cell. The contractility of muscle cells is mainly dependent on these myofibrils. Here, myofibrils, unlike striated muscles, are smooth and homogeneous, and the refractive ability is the same in all parts. Some smooth muscle cells become very small (22 – 25 microns). Such small cells fuse with each other by lateral appendages and form a syncytium. In this way, syncytiums, which are composed of smooth muscle cells, are especially seen where smooth muscle fibers cover large surfaces in a thin layer or join between other tissues and lengthen. The smooth muscle fibers in the walls bordering the organ cavities line up parallel to each other, forming beams and layers. Adjacent muscle fibers are interconnected by very thin membranes. These membranes ensure that the normal state of the fibers does not change during contraction and stretching. The thicker beams are surrounded by a connective tissue, and they attach to each other and to neighboring organs through this tissue. Some smooth muscle beams form musculo-elastic systems by attaching directly to elastic membranes through such elastic beams. In such systems, the elongation or shortening of the muscles changes the degree of elasticity of the fibers, and in this way the muscles governed by the nerves can actively adjust the effect of the elasticity force according to various situations.
Smooth muscle fibers, like other muscles, can grow in both length and thickness (hypertrophie) as a result of overwork. But the whole, like cells, only grows to a certain degree. For smooth muscle fibers, this limit is eight times their former volume. The growth of smooth muscle fibers in the uterine wall during pregnancy is not the result of overwork, but is due to the effect of hormones and is a preparation for childbirth. Smooth muscle fibers can also increase in number by dividing by mitosis. If they are underworked, smooth muscle fibers shrink and their number decreases (atrophy), as is the case with skeletal muscles. All smooth muscles receive their nerves from the autonomic nervous system.
Skeletal skeletal muscles are active elements of the movement system and create the necessary force for movement. This movement called muscle (musculus) makes a large part of the organs in terms of volume, muscle fibers that create the force and have the ability to contract called contractility. In addition, there are parts of the muscles called tendons (tendo, tendines) that show very different shapes in various muscles. The tissues that make up the beams are very different from muscle tissue in terms of both structure and function. The beams do not have the ability to contract and their role in the movement system is passive, their task is to transmit the force created by the muscle fibers to the skeletal parts.
Muscle Beams: Beams are auxiliary formations that transmit the force created by the muscles to the skeletal parts. The size and shape of the beams are very different according to the shape and functions of the muscles they belong to.
Thick collagen fibers form the most important part of the beam tissue. Several collagen fibers gather together in parallel to form thin beams. Between these fine beams are beam cells (fibroblasts). Thin beam beams combine with each other through the connective tissue to form thicker beams. Collagen fiber beams extend parallel to each other in short beams and in waves by making slight bends in long beams. When the muscle contracts, these waves disappear first and the beams straighten. After that, the muscle force transmitted by the beam fully exerts its effect on the bone and activates the bone. The ratio between the strength of the muscle and the ability to resist the pulling force of the beam was adjusted in favor of the beam in all muscles. No muscle can break its beam by its own strength alone. In cases of beam breakage, other forces must also have an effect.
Relationship between Muscle and Beams: The beams are not always located only at the ends of the muscles. Sometimes the beams cover part of the muscle in a flat layer, and sometimes they are inserted into the muscle in the form of beams of various lengths and thicknesses. The round beams seen only at the ends of the muscle also have extensions inserted into the muscle. In this way, the junction of the muscle cells with the beam becomes very large.
Various parts of the muscles: The thick parts of the muscles are called the ventricles. The place of attachment of one of the ends is called origo, and the other is called insertio. Of the attachment points, the point that does not move or moves less is considered the origin (origo) of the muscle.
The point that moves more and is called insertio is considered as the ending part of the muscle. In skeletal muscles, the point where one of the ends of the muscle sticks during movement usually remains fixed (punctum fixum). The point where the other end sticks moves towards the fixed point (punctum mobile). Mostly, the skeletal parts that remain fixed or move less are located closer to the middle of the body (proximal), and the parts that move a lot are located farther (distal). However, this situation may change as needed. The point that remains fixed during some movements becomes the punctum mobile during other movements of the same muscle. Origo does not always hit the punctum fixum, and insertio does not hit the punctum mobile. However, it is necessary and beneficial in terms of orientation that the names of the muscle ends are always the same.
The part of the muscle that is close to the starting end is called the head (caput). Some muscles have several parts that attach to several bones or to several faces of the same bone. These parts combine towards the middle or end of the muscle to form a general beam and they end by adhering to the bone through this beam. In this way, 2, 3 and 4 headed muscles are formed. Various parts of some muscles are connected to each other by the beam. In some muscles, such beams are in the form of round beams (m. digastricus), in others they are in the form of flat plates and are called intersectio tendinea (m. rectus abdominis). The various parts of the muscle and the condition of the tendons are adjusted according to the location of the muscle, topographical requirements, and the condition and function of the involved joints.
The thick parts of the muscles are mostly located away from the joints so that they do not interfere with the movement of the joints. For example, the thick parts of the muscles that move the fingers are located in the upper parts of the forearm, away from the finger joints, and the strength of the muscles is transmitted to the phalanges through thin long beams. If the thick muscles were located on or near the fingers, it would be impossible for the fingers to make wide and agile movements. However, there are thick muscles near the joints whose joint surfaces are suitable for wide movements in various directions, but some movements need to be braked. For example, in the shoulder and hip joint. The faces of these joints are conducive to very extensive movements. However, wide movements in some directions would be unnecessary, and some would even be harmful and dangerous to the condition of the hull. In such joints, thick muscles wrap around the joints, braking some movements and at the same time preventing dislocations.
The relationship between the structure and condition of the muscles and their function:
The most important factors affecting the function of the muscles are the number and length of the fibers that make up the muscle, and the way the muscle fibers adhere to the bones.
In order for a movement to occur, muscle strength must first overcome the weight force. Otherwise, although it works and produces a certain force, the muscle cannot shorten and the attachment point remains motionless. For example, if we take a heavy object in our hand and want to bend our forearm, if the force created by the muscles that make this movement is not enough to overcome the weight force, our forearm will remain motionless. Meanwhile, all the force created by the muscles was used only to lift the weight. Then, for the movement to occur, the muscles that make the movement need to generate more kinetic energy.
Each of the muscle fibers that make up the muscle works as a separate motor and creates kinetic energy by burning the nutrients that come with the blood. Therefore, the strength of the whole muscle must depend on the size and number of motors, that is, the thickness and number of muscle fibers. Therefore, the strength of a muscle is measured by the sum of the transverse sections of all the fibers that make up the muscle, and this sum is called the physiological section of the muscle.
As a result of continuous work, muscle fibers thicken and multiply (hypertorphy and hyperplasia). Such muscles generate more strength and can do heavier work.
The transverse section made from the thickest part of a muscle is called the anatomical section of the muscle. If all the fibers that make up the muscle are of the same length and parallel to each other, the size of the anatomical and physiological sections will be the same, and in such muscles we can determine the strength of the muscle according to its thickness. But this is seen in very few muscles. In most muscles, the length of the fibers is not the same, nor are their states parallel to each other. In such muscles, it is impossible to make a single section that hits all the fibers, and many muscle fibers that generate the force are outside the section. Therefore, it is not correct to make a judgment about the strength of the muscle according to the thickness of the muscle. In thin, flat and wide muscles, the separation of anatomical and physiological sections is very large and the thickness of the muscle in such muscles cannot give any idea about the strength of the muscle.
Angle of insertion: Not all of the force produced by the muscle is often used for movement. The amount of force used for movement depends on the width of the angle formed between the beam and bone at the point of attachment. The wider this angle, called the insertion angle, the greater the effect of muscle strength on the insertion point. When the insertion angle reaches 900, all of this muscle strength is used for movement. In such cases, muscles with not much physiological cross-section can also mobilize heavy body parts (such as the external rotator muscles of the thigh).
Most of the muscles in the human body attach to the bone by making an acute angle. The muscle force acting on the attachment point of such muscles during contraction is divided into two according to the resultant force law. Some of the force exerts a pulling effect on the bone in the direction of the beam and moves the bone. The other part acts in the direction of the bone axis, pulling the bone towards the joint and bearing the weight. In heavy parts such as the lower extremities, the insertion angles of all the long muscles coming from above are narrow.
Direction of movement: We have seen about the joint that movements can be made in two opposite directions around each axis (flexion and extension around the transverse axis, external and internal rotation around the vertical axis, abduction and adduction movements around the sagittal axis).
While detecting the direction of movements, it should be kept in mind that the moving point will approach the stationary point and follow the closest path during the movement.
Muscles that move in the same direction are called synergists, and those that move in the opposite direction are called antagonist muscles. When a muscle contracts, its antagonist pulls and lengthens. This withdrawal acts as a warning, creating a degree of tension in the antagonist muscle as well. The degree of this tension can vary according to the need. Sometimes the antagonist brakes the movement by increasing the muscle tension, and sometimes it can stop it completely when necessary. These events are governed by the central nervous system and are optimally adjusted for the needs of the situation and the benefit of the body. If the antagonist muscles work at the same time and with the same force, no movement occurs and the bone is fixed in a particular state.
Tone: Muscles in living things always maintain a certain degree of tension during rest. Like all objects, the human body and its various parts are constantly under the influence of gravity. This force, which is in the nature of a permanent stimulus, acts on the muscles through reflex and brings the muscles to a state of slight but permanent tension. This constant tension that the muscles maintain during rest is called tone. Muscle tone creates the force that opposes the force of weight and allows our body and its various parts to stay in certain situations. Gravity is constantly pulling our torso forward and down, and without the muscle tone that counteracts this force, our body would not be able to maintain its upright position. The resting state of various parts of our body is also determined by the tone of the muscles belonging to these parts. Not all muscles have the same tone. While our arms are at rest and hanging down, our forearms remain in a slightly flexed state. This shows that the tone of the flexors is relatively higher than the extensors. Generally, the more used muscles have a higher tone. The degree of tonus is also very different according to the person, and the differences in body posture in humans are due to tone differences. Even in the same person, muscle tone changes for various reasons. Apart from physical events such as fatigue, various mental states such as joy, excitement, distress and fear also have important effects on muscle tone.
Shape and movements of the spine: Vertebral column, which is responsible for carrying the weight of the head and body and performing the support function, is not in the form of a straight column, but shows curvatures in various parts and in different directions. Among these curvatures, the most important in terms of function are sagittal curvatures. Humans have four sagittal curves of the spine, two anteriorly and two posteriorly convex. Of these, those of the cervical and lumbar parts are convex anteriorly, those of the thoracic and sacral parts are posteriorly convex. In this respect, there are important distinctions between the human spine and the quadrupedal spine.
In quadrupedal animals, the posteriorly convex part of the spine, which forms the thoracic, lumbar and sacral parts, is the most important in terms of bearing the weight of the body and internal organs. This part of the spine, like a bridge arch, transmits weight to both the fore and hind legs at the same time and rests on solid supports on both sides. Therefore, the balance is stable (stable balance) in quadrupedal animals. The cervical part of the spine, which bears the weight of the head alone, develops differently depending on the type of animal and the length of the neck, and becomes an elastic column with varying numbers of curvatures.
The adjustment of balance in humans and the reason why the shape of the spine is different from animals in relation to this event is that humans move on two legs. The load of the head and body weight on the spine by standing on two legs completely changed the balance situation. With the effect of these factors, the typical curvatures seen in humans occur and the final shape of the spine gradually occurs. The typical curvature of the spine in newborns is negligible.
Since the spine does not have the qualities to balance the head and trunk, the child cannot keep his head and trunk upright in the first months after he is born. After a while, with the development and strengthening of the neck and back muscles and spinal ligaments, the neck part of the spine becomes an elastic column that can carry the weight of the head and provide balance. At this time, a forward-facing neck curvature (cervical lordosis) occurs in the neck part of the spine. This curvature, which is caused by the weight of the head on one hand and the forces that provide the vertical position of the spine on the other hand (muscle strength and the elasticity of the ligaments), puts this part of the spine in a spring state and facilitates the carrying of the weight of the head and providing the balance. accustomed to sitting. When the child stands up, the situation between the presacral vertebrae and the sacrum and pelvis changes, and at the same time, the weight of the head and trunk is transferred via the pelvis to the lower parts, which until then were free from the task of bearing weight. The sacrum, which is attached to the pelvis bones during standing up, also changes its position a little with the whole pelvis, but it cannot fully follow the presacral vertebrae that take a vertical position. Therefore, the slight bend seen between the sacrum and the lumbar part of the spine in intrauterine life due to the concavity of the sacrum increases and the projection called the promontorium occurs. After a while, with the weight of the trunk and the effect of the sacrospinal muscles, which are gradually developing and getting stronger, a second curvature (lumbar lordosis) occurs in the lumbar part of the spine, the convexity of which faces forward. As in the neck piece, the strength of the muscles resisting the weight and the elasticity of the ligaments have important effects in determining the shape and degree of the lumbar lordosis. The most prominent point of this curvature is at the height of the fourth lumbar vertebra. Lumbal lordosis turns the lumbar part of the spine into an elastic spring that carries the weight of the trunk and helps maintain balance.
If the lumbar lordosis, which occurred as a result of standing on two legs, had continued in the chest part, our heavy organs housed in the abdominal and thoracic cavities would have come too far, and this would have made it difficult to maintain balance. The occurrence of this unfavorable situation was prevented by the occurrence of another curvature in the opposite direction between the neck and waist curvatures. This curvature starting from the sixth and seventh neck vertebrae to the eleventh and twelfth thoracic vertebrae and its convexity facing backward is called thoracalkyphosis. With the occurrence of thoracic kyphosis, the thoracic cavity is enlarged in the sagittal state, and at the same time, the weight of the organs in this cavity and the upper parts of the body suspended in the upper part of the body is partially pulled to the back.
These curvatures of the spine occur in young children only at the time of function, that is, when they are standing, and disappear again as the child grows taller. Then, gradually, the shapes of the vertebral corpuscles and especially the intervertebral discus begin to develop in accordance with the curvatures, and certain forms of the curvatures appear and remain permanent towards puberty. Meanwhile, the development, length and degree of tension of the ligaments, which play an important role in the formation and preservation of curvatures, are adjusted in accordance with the general condition and shape of the spine.
The typical curvature of the spine does not occur in people who have never stood up due to illness and who spend their whole lives in bed. In old age, the spine is often shortened due to thinning of the vertebral corpuscles and intervertebral discus. With the change of weight effect, the shape of the vertebral corpuscles also changes. Especially in the thoracic part, the anterior parts of the corpus become thinner, and therefore the posteriorly convex curvature of this part increases and a humpback occurs. Thinned discus may partially ossify in old age. With the effect of all these changes in the vertebrae, the effect of the weight falling on the pelvis and hip joints also changes. As a result, the posture of the whole body and the gait of the person take on a form reserved for the elderly. Due to the decrease in the elasticity of the spine, it is necessary to exert more muscle strength, the person gets tired quickly and many movements become difficult.
Apart from sagittal curvatures, the spine also shows slight curvatures to the right and left in the frontal direction in humans. These curvatures, called scaliosis, are not seen in young children and only occur between the ages of 7 and 10.
The spine is not in the form of a straight column or a curved curve in one direction only, but it is very important in terms of carrying weight and providing balance, that it curves in various directions and shapes. If the spine were in the form of a single arch, when it bends too much with the increase in weight, the effect of all the weight will be gathered at the most protruding point of the convex side of the arch, and the vertebrae and ligaments here would be under the influence of too much weight. In the spine that makes many curves, the same weight is distributed with many curves and in this way, the task that falls on the individual parts is reduced. If the spine were in a straight column, most of the response from the ground against the pain during walking would be transmitted directly to the base of the skull, and our head and brain would be shaken with each step we took. Especially since it was the elastic spring that reduced the increased response during jumping, the force acting on the skull base would be too much and even the upper end of the spine could be inserted into the skull by breaking the bones. As a matter of fact, the curvatures and elasticity of the spine are not enough to disperse and alleviate the excessive reaction in people who fall on their feet from a very high height, and they are inserted into the skull by breaking the spine base.
All parts of the spine cannot move in all directions and to the same degree, mainly because the shapes and conditions of the faces of the intervertebral joints in various parts and their directions are different.
Although the movements that can be made between vertebrae close to each other are very few due to the shape and condition of the joint surfaces and the strong restraining effects, the spine can make wide movements in a wide variety of directions by combining the movements performed at the same time in many joints. The fact that the movements of the spine are distributed over many joints and the movements between the adjacent vertebrae are low is very convenient for the protection of the spinal cord. During movement, the shape of the spine changes and the spinal cord in the vertebral canal has to comply with this situation. If two or more adjacent vertebrae move too much and change their state too much, the shape of those parts and canalis vertebralis (vertebral canal) would change suddenly, and the spinal cord, which had to conform to the canal, would be bent and risked to be ruptured or damaged.
The articular surfaces of the neck vertebrae are flat or slightly concave and inclined from front to back. The curvature of the joint surfaces is approximately 45°. Although these conditions of the faces are in different degrees, they give the neck vertebrae the opportunity to move in almost every direction. They are similar to those of the thoracic vertebrae, but in a different situation. Here, the articular surfaces are close to the frontal and slightly turned to each other. The frontal positions of the articular surfaces are not suitable for forward and backward bending movements, and these movements are very few in the chest part of the spine, especially in the middle part. Lateral bending movements are relatively less in the neck part, but it can be done and it gets wider as it goes up. In the lumbar part of the spine, the articular surfaces are close to the sagittal and therefore rotational movements in this part are almost impossible. The most common movement in this piece is leaning forward and backward.
Turning the spine to the right and left around a vertical axis can be done mostly in the neck part and decreases as it goes down. The sagittal states of the articular projections of the lumbar spine are not suitable for rotational movements. Therefore, if the pelvis remains fixed while people are making right or left rotational movements, only the part of the body above the navel participates in the movements. Fakat genellikle omurganın bütün parçalarının katılması ile genişler hareketler yapıldığı zaman pelvis de harekete katılır ve hareketlerin önemli miktarda genişlemesini sağlar. Bilhassa öne doğru eğildiğimiz zaman pelvis’in de kalça eklemleri aracılığı ile yaptığı bütün hareketler omurganın durumuna etki yapar. Ayakta durduğumuz zaman bütün hareketler sırasında pelvis hareket merkezi görevini yapar ve gövdenin temel desteğini yapan omurganın durum ve hareket lerinin ayarlanmasında çok önemli rol oynar. Bundan dolayı pelvis ile gövde alt taraf kemikleri arasında çok sayıda ve kuvvetli kaslar bulunur.
Üç esas eksen etrafında yapılan bu hareketlerin birleşmesi ve pelvisin de katılması ile gövdenin sirkumduksiyon denilen dönme hareketi meydana gelir.
Omurga aynı zamanda çeşitli parçaları ile çeşitli yönlerde hareketler de yapabilir. Örneğin bel parçasını öne ve aynı zaman da göğüs parçasının üst kısmıyla boyun parçasını arkaya doğru eğebiliriz.
İskelet Kaslarının Adlandırılması Ve Sınıflandırılması
Vücudumuzda bulunan yaklaşık 600 kas şekil,boyut, yerleşim özelliği, yapışma yerleri, fonksiyonları ve çalışma düzeni özellikleri dikkate alınarak adlandırılıp sınıflandırılmıştır.
Bazı kasların adlandırılması gövde şekline göre yapılmıştır. Kare şeklindeki kaslar quadrat kas (Örneğin, m. quadratus lumborum).çember şeklindeki kaslar orbicüler kaslar (Örneğin, m. orbicularis oris) silindirik kaslar teretik kaslar (Örneğin, m. teres majör) olarak adlandırılmıştır.
Kaslar sahip oldukları kas liflerinin düzenlenişine göre de dik seyirli (Örneğin, m.rectus femoris) oblik seyirli (Örneğin, m. obliguus externus) ve horizontal seyirli (Örneğin, m. transversus abdominis) kaslar olarak adlandırılmıştır. Kas lifleri çekme hattına oblik olarak yerleşmişse pennat kaslar denir. Pennat; kasların, unipennat, bipennat (Örneğin, m. rectus femoris) ve multipennat (Örneğin, m. deltoideus) tipleri vardır.
Kaslar yerleşim yerlerine göre yüzeyel ve derin, içyan, dışyan, ön ve arka grup infa ve suprahyoid vb. şekilde gruplanmışlardır. Benzer şekilde m.supraspinatus ve m.infraspinatus spina scapulae’ye göre adladırılmıştır.
Bazı kaslar, yapışma yerlerine göre adlandırılmıştır. Örneğin, m. sternothyroideus, m. omohyoideus ve m. coracobrachialis’in adlandırılması bu şekilde yapılmıştır.
Fonksiyonlarına göre kaslar, fleksor, ekstensor, adduktor, abduktor ve rotator kaslar olarak 5 gruba ayrılmıştır. Örneğin, radiokarpal eklemde fleksiyon hareketi yaptıran bazı önkol ön grup kasları m. flekor carpi ulnaris vb.adlandırılmıştır.
Çalışma düzeni yönünden de kaslar esas hareket ettirici (prime mover). Antagonist, fiksator ve sinerjisi kaslar olarak gruplanırlar. Belli bir hareketin yapılmasında esas rolü üstlenen kasa/kaslara prime mover kas/kaslar denir. Örneğin, diz eklemi ekstensiyonunda m.quadriceps femoris prime mover olarak rol oynar. Prime mover kas/kasların hareketine zıt olarak çalışan kaslara antagonist kaslar denir. Esas hareket ettirici (prime mover) kas kasların etkili ve verimli bir şekilde çalışabilmesi için prime mover kasın başlangıcını sabitliyen kaslara fiksatör kaslar denir. Fiksatör kasların özel bir grubunu oluşturan sinerjist kaslar, prime mover kasın hareketi esnasında orta pozisyonda kalan eklemlerde istenmeyen hareketleri engelleyen kaslardır.
Sağlıklı günler dileği ile…
Uzman Dr.Ali AYYILDIZ – Veteriner Hekim – İnsan Anatomisi Uzmanı Dr. (Ph.D.)
