Types of muscle contractions. Three types of muscle contractions are distinguished according to the method of muscle shortening:
1) isotonic, in which the fibers shorten under a constant external load, rarely manifests itself in real movements(since the muscles shortening at the same time change their tension);
2) isometric – is a type of activation in which a muscle develops tension without changing its length. The so-called static work of the human motor apparatus is built on it. For example, in the isometric contraction mode, the muscles of a person who pulled himself up on the crossbar and holds his body in this position work;
3) auxotonic or anisotonic – this is the mode in which the muscle develops tension and shortens. It is this type of muscle contraction that ensures the performance of human motor actions.
Anisotonic contraction has two types of muscle contraction: in overcoming and yielding modes.
In overcoming mode the muscle shortens as a result of the contraction (for example, a runner's calf muscle shortens in the take-off phase).
In submissive mode the muscle is stretched by an external force (for example, the calf muscle of a sprinter during the interaction of the leg with the support in the depreciation phase).
Figure 1 shows the dynamics of muscle work in overcoming and yielding modes.
The right side of the curve displays the patterns of overcoming work, in which an increase in the speed of muscle contraction causes a decrease in traction force.
In the yielding mode, the opposite picture is observed: an increase in the speed of muscle stretching is accompanied by an increase in traction force (which is the cause of numerous injuries in athletes, for example, Achilles rupture).
At a speed equal to zero, the muscles work in isometric mode.
For the movement of a link in a joint under the action of muscle forces, it is not the forces themselves that are important, but the moments of forces created by them, since the movement of the link is nothing more than rotation about the axis passing through the joint. Therefore, the types of muscle work can be expressed in terms of moments of forces: if the ratio of the moment of internal forces to the moment of external forces is early to unity, the contraction mode will be isometric, if it is more than unity, it will overcome, if it is less than unity, it will be inferior. Joint support can be provided with sports tape.
Group interaction of muscles. There are two types of group muscle interaction: synergism and antagonism.
Muscles-synergists move the links of the body in one direction. For example, the biceps brachii, brachialis and brachioradialis muscles are involved in bending the arm at the elbow joint. As a result of the synergistic interaction of muscles, the resulting force of action increases.
Antagonist muscles have a multidirectional effect: if one of them performs overcoming work, then the other performs inferior work. Muscles provide reciprocating-rotational movements of the links of the body, since each of them works only for contraction; high accuracy of motor actions, since the link must not only be set in motion, but also slowed down at the right time. Antagonists consist of a pair: an agonist (flexor) - an antagonist (extensor).
Power and efficiency of muscle contraction. As the speed of muscle contraction increases, the traction force of the muscle functioning in the overcoming mode decreases according to the hyperbolic law (see Fig. 1). It is known that mechanical power is equal to the product of force and speed (N = F V). There is a force and speed at which the power of muscle contraction is greatest; this mode occurs when both force and speed are approximately 30% of the maximum possible values.
Accumulation of elastic deformation energy in stretched muscles and tendons. When a muscle contraction is preceded by a stretching phase, the forces, power and work produced are greater than when contracting without pre-stretching. After stretching, the rate of contraction increases due to the rate of recovery of the elastic components of the muscle.
Stretching the musculotendinous system also makes it possible to accumulate and use the energy of elastic deformation. It has been calculated that the Achilles tendon stretches 18 mm during a run at an average speed of 42 joules of energy. Elastic stretch will make a significant contribution to muscle performance only if active muscle stretch is immediately followed by an overcoming mode of muscle contraction. The higher performance of the squat jump compared to the jump from a static pose shows the advantage of pre-stretching the muscles.
Muscle physiology. Classification of muscles according to structural, biochemical and functional criteria
The composition of the muscle tissue of the human body includes striated (skeletal and cardiac) and smooth muscles. The first type of muscles ensures the maintenance of the posture, position in space and the movement of the body and its parts in it. The functions of smooth muscles are to maintain blood pressure, move food masses and remove end products of metabolism. The heart muscle consists of transversely striated mononuclear muscle cells, but has different properties compared to striated skeletal muscles. The regulation of tone and contractile activity of smooth muscles is carried out by the sympathetic and parasympathetic nervous systems. Skeletal muscle contractions occur in response to nerve impulses coming from the spinal cord.
There are more than 600 muscles in the human body, their share of the human body weight is approximately 30% (35-45% in men and 28-32% in women).
Main functional properties of muscles:
1) excitability;
2) conductivity;
3) contractility.
Excitation and contraction of muscles is carried out under the influence of nerve impulses coming from the nerve centers. In muscles, the chemical energy stored in the form of ATP is converted directly into mechanical and thermal energy.
The muscle consists of the abdomen (the contractile part, built from striated muscle tissue) and tendons, which attach the muscle to the skeleton.
Skeletal muscle groups:
1. By shape- narrow and wide. In narrow (fusiform) muscles (for example, on the limbs), the tendons are narrow and long, in wide (ribbon-shaped, for example, on the anterior abdominal wall) tendons are wide and are called aponeurosis.
2. According to the location of the muscle bundles:
Cirrus - in them muscle bundles they are attached to the tendon on one or both sides, as in a bird's feather, and on the other hand they diverge. These muscles are able to contract strongly, but over short distances (strong muscles).
Muscles with a parallel arrangement of long muscle bundles. These muscles are not very strong, but can shorten up to 50% of their length (dexterity muscles).
3. According to the function performed and the effect on the joints: flexors and extensors, adductors and abductors, constrictors (sphincters) and dilators.
Exists two kinds muscle contractions - single and tetanic. single muscle contraction is the only type of contraction for the heart muscle, and in skeletal muscle it has an artificial etiology and occurs in response to a single electrical signal and the occurrence of an action potential (AP). Such a contraction, lasting » 100 ms, has a waveform (see Fig.) and includes three phases: 1 - a latent period (from 2-3 to 10 ms), lasting from the moment of application of irritation to the start of contraction, 2 - a shortening phase or contraction (40-50 ms) and 3 - relaxation phase (about 50 ms). Under natural conditions, the impulses do not come singly, but in series of at least 15-50 impulses / s, to which the muscle responds with the appearance tetanic contraction(tetanus). It is based on the phenomenon of summation of several single contractions. Depending on the frequency of impulses, dentate and smooth tetanus are distinguished.
Figure 5 - Types of muscle contractions:
A - phases of a single contraction; B - solitary and tetanic contractions
jagged tetanus(incomplete) occurs when each subsequent impulse comes into the phase of muscle relaxation.
If the frequency of stimulation is higher, and each subsequent impulse enters the phase of muscle shortening, then full summation occurs, and the tetanic contraction is of a continuous nature - smooth tetanus(full).
An increase in the response under the action of submaximal stimuli to a certain (maximum) level occurs due to the involvement of new, previously unused fibers in the process of excitation. In the case of a further increase in irritation (supermaximal level), the response no longer increases, and vice versa, with very strong stimuli (5-10 or more thresholds), a pessimal response can be achieved.
In the whole organism, motor neurons send bursts of action potentials to motor units, which contract tetanically in response. Skeletal muscles are in a state of constant tone due to constant background impulses from the motor zones of the CNS.
Muscle work(A) is the product of the load (F) and the distance (h). A \u003d F * h, or A \u003d F * dl, where dl is the amount of muscle shortening.
Relative muscle strength determines the maximum load that the muscle can lift. This value is much more dependent on the thickness of the muscle than on its length.
The strength of muscle contraction is determined by the number of muscles involved in the contraction process. motor units. Absolute Power- this is the ratio of relative strength to the cross-sectional area of \u200b\u200bthe muscle, expressed in cm 2. For example, the absolute strength of the biceps is 11.9 kg∕cm 2, calf muscle- 5.9 kg∕cm 2.
To assess the functional activity of muscles, they talk about their tone and phasic contractions.
Tone- a state of continuous continuous tension.
phasic Muscle contractions are called short-term shortening of the muscle, followed by its relaxation.
The amount of contraction (degree of shortening) of the muscle depends on its morphological properties and physiological state. The greater the thickness of the muscle, the greater the load it can lift during its contraction. Long muscles contract more than short ones. Moderate stretching of the muscle increases its contractile effect, with strong stretching, muscle contraction weakens.
Average load rule : maximum muscle work occurs when medium , and not the maximum load values, since
at higher loads, fatigue quickly develops.
Modes of muscle contractions:
1) isotonic- a contraction in which shortening occurs muscle fibers, but the same tension will remain (for example, when lifting a load);
2) isometric- a contraction in which the length of the muscle fibers does not change, but the tension in it increases (for example, with pressure resistance);
3) auxotonic- a contraction in which both the tension and the length of the muscle change.
The strength of muscle contraction is determined by the number of active muscle fibers involved in the contraction, the frequency of nerve impulses and the presence of synchronization of the activity of individual muscle fibers in time. Even at rest, skeletal muscles are rarely completely relaxed. They usually hold some tension. tone. Muscle tone increases after heavy physical exercise and during psycho-emotional stress.
With regular physical training the number of muscle fibers does not change, but their diameter increases due to an increase in the number of myofibrils in the fibers.
Muscular work is associated with significant energy costs and, therefore, requires an increased supply of oxygen. This is achieved by activating the activity of the organs of the respiratory and cardiovascular systems. Strengthening metabolic processes during muscular work leads to the need for increased excretion of metabolic products, and, accordingly, increased activity of the kidneys and sweat glands. Consequently, physical exercise increase the activity of physiological systems, have a stimulating effect on the motor system, lead to the improvement of motor skills, the development of mental functions. With hypodynamia in children, metabolic processes suffer, immunity, working capacity, including mental, decrease.
Muscle fatigue depends on the supply of oxygen and blood to it. The efficiency of using O 2 by the muscle is 20-25%, and with training it can reach 30%.
In each muscle, there are many motor, or motor units - a certain number of muscle cells innervated by one nerve cell, and each myocyte has its own nerve ending.
Among the motor units, there are: fast ones, which include an average of about 50, and slow ones - from several hundred to thousands of muscle cells.
Types of nerve fibers:
1) slow, restless(red, static, tonic) - these are thin, rich in blood vessels and myoglobin muscles, during work they show great strength, do not get tired for a long time, but the speed of their contractions is small. For example, they maintain vertical statics, hold certain parts of the body in a certain position, i.e. perform a supporting function. They also include the external muscles of the eyeball. Slow phasic contractions provide muscle tone, and therefore such contractions are called tonic. They are necessary to maintain balance in static and dynamic. Slow muscle cells make up the bulk of the motor units. They have a lot of myoglobin and myosin, where oxidation occurs. Such muscles are red in color and get tired a little.
2) fast, easily fatigued(white, dynamic, phasic): they have thick muscle bundles, fewer blood vessels and myoglobin, their rate of contraction is high as well as fatigue. Yielding in strength, they are able to produce a variety of small quick movements. Fast phasic aerobic muscles are slightly paler, since they contain less myoglobin, but a sufficiently large amount of myosin is still retained, and, consequently, oxidation processes proceed intensively. In such muscles, fatigue develops faster than in those described above. In terms of the number of muscle cells in a motor unit, fast phasic muscles take second place after slow ones. Anaerobic muscles provide the fastest contractions. They are low in myoglobin and myosin. The cells that make up fast anaerobic muscles are white. Anaerobic glycolysis occurs in such muscles, therefore, as a result of the accumulation of under-oxidized products (lactic acid), oxygen debt develops, and as a result, the fastest fatigue. An example of such muscles are the muscles of the fingers and eyes.
3) fast, fatigue resistant(intermediate).
All three types of fibers can be contained in the same muscle, and the ratio of their number is determined to a large extent by heredity. For example, in the human quadriceps femoris, the percentage of slow fibers can be from 40 to 98%. The more slow fibers, the more the muscle is adapted for endurance work. Conversely, people with a high percentage of fast strong fibers are more capable of doing work that requires a lot of strength and speed of muscle contraction.
The strength of muscle contraction is determined by the number of active muscle fibers involved in the contraction, the frequency of nerve impulses and the presence of synchronization of the activity of individual muscle fibers in time. Even at rest, skeletal muscles are rarely completely relaxed. Usually they retain some tension - tone. Muscle tone increases after heavy physical exercise and during psycho-emotional stress.
Hello, my dear readers, admirers and other good and not so personalities! Today we are waiting for an archival and necessary note of a scientific or so direction. We will talk in it about the types of muscle contractions, what they are, what they are and how to use them in your daily training activities.
So, make yourself comfortable, let's start gesturing.
Types of muscle contractions: what, why and why
If you are not aware yet, then the ABC of Bodybuilding project is an educational resource, and therefore unusual in-depth articles periodically slip on it, revealing the essence of various pumping (and related) processes. In particular, the last such notes include:, and others like them. So, in matters of changing your own body, it is important not just to mindlessly pump irons and lift heavy weights, it is important to understand what is happening in the muscles at this particular moment, what type of load is applied to them and what it can eventually result in. In general, today we will invest in our head in order to pump our body even better later. Actually, let's get to the point.
Note:
For better assimilation of the material, all further narration will be divided into subchapters.
Types of muscle contractions: how it happens
Every time you pick up a projectile (eg dumbbell) and start exercising (for example, lifting a dumbbell for biceps), the process of contraction of skeletal muscles occurs. We are in previous posts (particularly in this one) we have already considered how the process of muscle contraction itself occurs, therefore, in order not to repeat myself, I will give only a general scheme.
…and visual animation (click and run the application by pressing "play").
The motor center (motor unit) consists of a motor neuron and a certain number of innervated fibers. Muscle contraction is the response of a muscle unit to the action potential of its motor neuron.
Total exists 3 types of graded muscle responses:
- wave summation - is formed by increasing the frequency of the stimulus;
- multi-element summation (multiple motor unit summation)- formed by increasing the strength of the stimulus (increased number of motor neurons);
- stairs (treppe) - a reaction with a certain frequency / strength to a constant stimulus.
Speaking of muscles, one cannot fail to mention muscle tone - a phenomenon in which the muscles show a slight contraction even at rest, while maintaining their shape and ability to respond to the load at any moment. You do not have to memorize all this, it will simply help you better understand the essence of the ongoing processes in the muscles with different types of muscle contractions.
What are the types of muscle contractions
Did you know that in order to ensure better muscle growth, they need to be given different types of load, but not in the sense of weights or changing one exercise to another, but in different ways to influence the characteristics of the muscles. This is what we are talking about - static and dynamic contraction of skeletal muscles. Static and dynamic work combine five types of muscle contractions, each of which is divided into two forms of movement: concentric and eccentric.
Let's go through each in order and start with...
Dynamic contractions (DS)
Occur during movement or using free weights - when the lifter lifts a free weight and resists gravity. The most common type of DS is isotonic, in which the muscle changes its length as it contracts during movement. Isotonic contractions (IS) allow people (and animals) to carry out their usual activities, to move around. There are two types of IS:
- concentric - the most common and frequently encountered in everyday and sports activities. Imply shortening of the muscle due to its contraction (compression). An example is flexion of the arm at the elbow joint, resulting in a concentric contraction of the muscle of the biceps brachii, the biceps. This contraction is often referred to as the positive phase of the projectile's rise;
- eccentric is the exact opposite of concentric. Occurs when a muscle lengthens during contraction. It occurs much less frequently in pumping practice and involves the control or slowing of movement on the initiative of an eccentric muscle agonist. An example is when kicking a ball, the quadriceps contract concentrically, while the hamstring muscles contract eccentrically. Lower phase (extension/lowering) when lifting a dumbbell for biceps or in pull-ups are also examples of ES. This type puts more strain on the muscle, increasing the chance of injury. This contraction is often referred to as the negative phase of projectile descent.
The features of eccentric contractions include a large generation of force - i.e. the athlete can reduce (in managed mode) a weight far exceeding in “tonnage” its operating lifting weight. Greater strength is provided by greater inclusion of type 2 fibers (fast muscle fibers). Thus, the exercise of concentrated lifting of the dumbbell to the biceps, or rather its negative phase, allows you to more actively include white fibers in the work. This feature is often used by advanced athletes to improve explosive strength, for example, in the bench press.
Note:
The muscles become 10% stronger during eccentric movements than during concentric contractions.
Most often in such cases, a dumbbell is taken, which is far from the usual weight. (let's say 15 kg) on the 3-7 kg. The positive phase is carried out by throwing the dumbbell up with the help of a partner or other hand, and the negative phase takes about 4 sec (against 2 lift sec). Such eccentric training is sometimes very useful, because. create extensive damage to muscle fibers, which leads to an increase in protein synthesis, subsequently the phenomenon of supercompensation and better muscle hypertrophy. Their minus is a high probability of injury. (if you do everything without a head) so it's better for beginners not to bother.
Static abbreviations (SS)
The name itself speaks for itself, static, i.e. no movement, no change in lengthening/shortening. Such contractions are called isometric. Example - holding an object in front of you (bags in the store) when the weight is pulling down, but the muscles are contracting to keep the object at the right level. Also a great example of isometric muscle contraction is hanging at some point in the trajectory for an indefinite time. For example, when doing squats in the middle of the trajectory (half up) quadriceps contract isometrically. The amount of force generated during an isometric contraction depends on the length of the muscle at the point of contraction. Each muscle has an optimal length for maximum isometric strength. The resulting force of isometric contractions exceeds the force produced by dynamic contractions.
For clarity, I will give examples demonstrating different types of muscle contractions (clickable).
We have considered the main types of abbreviations that are most common in training practice, however, if you look at the initial classification, there are several more of them. Let's also analyze them so that you at least have an idea about them and can surprise your ignorant colleagues in the hall :).
Isokinetic contractions (Isokinetic)
In isokinetic contractions (Iso=constant, kinetic=movement) neuromuscular systems can work at a constant speed at each stage of movement against a given resistance. This allows the working muscles and muscle groups to create a high degree of tension throughout the range of motion. This type of contraction is effective for the uniform development of muscle strength at any angle of movement. These are dynamic contractions, and during them the length of the muscle changes. The defining characteristic of muscle IS is that it results in movements at a constant speed.
AT gym a similar type of contraction is used on special isokinetic simulators-dynamometers Cybex, Nautilus and others. Swimming and rowing, constant speed activities, are also an isokinetic form of contraction.
The benefits of isokinetic contractions are as follows:
- lead to an improvement in neuromuscular coordination, increasing the number of fibers involved in the work;
- lead to an increase in muscle strength of the entire muscle throughout the entire range of motion;
- movement speed control can significantly reduce the likelihood of injury, which is especially important in postoperative and rehabilitation periods;
- lead to improved overall endurance and cardiac function.
Oxotonic contractions (Auxotonic)
This is a dynamic type of high tension contraction. (increase in tension). When an athlete flexes their arms while holding the barbell, its mass apparently does not change throughout the entire range of motion. The force required to perform this movement is not constant, it depends on the physique, the leverage of the athlete, the angle of the limbs and the speed of movement.
Pliocentric contractions (Plyocentric)
It is a hybrid (combination), the muscle performs isotonic contraction from a stretched position. An activity that uses this type of muscle contraction to the fullest is called plyometric training or. This type of activity combines well with the strength and power of the athlete, and is often recommended as the basis of women's training.
So, in order to finally settle all of the above, I will give a combined picture-presentation (which I found in the archives of a foreign sports medical university) types of abbreviations. Here, in fact, is she (clickable).
Influence of types of contractions on muscle length
The result of isotonic contractions is a change in muscle length (at constant force). Concentric IS shorten the muscle as the load is transferred, eccentric IS lengthen the muscle as it resists the load. The result of isometric contractions is an increase muscle tension, however, neither lengthening nor shortening of the muscle occurs.
In a visual form, all this disgrace looks like this.
Type of muscle contractions while running
We analyzed the types of muscle contractions depending on the activity, however, the following question remained unconsidered: what type of contractions takes place in running. In general, errands are a universal tool that covers several types of contractions at once, in particular: isotonic concentric and eccentric. Contractions occur within slow and fast twitch muscle fibers.
During running, lifting the hip and flexing the knee results in concentric isotonic contractions of the hip and hamstring flexors. (muscles of the back of the thigh). As you straighten your leg to push off the ground and make a propulsion motion, your hip extensors (hamstrings, gluteus maximus) and knees (quadriceps) perform concentric isotonic contractions.
Eccentric isotonic contractions are especially involved in downhill (downhill). During normal running, the knee extensors and quadriceps contract to straighten the leg. When running downhill, the quads contract eccentrically. In addition, the tibialis anterior also contracts eccentrically, controlling the downward movement of your foot after the heel hits the ground. As for the involvement of different types of fibers during running, the errands at a relatively calm pace ( jogging) uses mainly slow-twitch fibers for their muscle activity. Increasing your speed allows you to recruit more fast-twitch muscle fibers.
What are basic exercises?
In fact, knowledge about the types of muscle contractions should even more incline athletes (especially beginners) towards the execution of the base, and here's why.
Many skeletal muscles contract isometrically to stabilize and protect active joints during movement. While when performed, the quadriceps femoris muscle contracts concentrically (during the ascending phase) and eccentrically (in descending phase), many of the deeper thigh muscles contract isometrically to stabilize the hip joint during movement.
Thus, working with basic exercises, you can immediately drive muscle groups through several types of contractions. In fact, this will have a positive effect on their volumetric and power characteristics and will give a better incentive for growth.
Well, perhaps, that’s all for today, all topics are covered, the questions are considered, the children are fed, so it’s time to round off.
Afterword
Another one has come to an end, who knows what, according to the score :) note, in it we talked about the types of muscle contractions. Someone may say that it is not practical - perhaps, but the theory and understanding of all pumping processes are also very important in building a shaped body, so we absorb it!
That's all for now, let me take my leave, until we meet again!
PS. Friends, do you use this information in your training, or did you not know anything about it until now?
P.P.S. Did the project help? Then leave a link to it in the status of your social network - plus 100 points to karma, guaranteed :) .
With respect and gratitude, Dmitry Protasov.
Isometric muscle contraction contraction of a muscle, expressed in an increase in its tension with a constant length (for example, contraction of a muscle of a limb, both ends of which are fixed motionless). In an organism to And. the tension developed by the muscle when trying to lift an unbearable load is approaching. Wed Isotonic muscle contraction.
Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what "Isometric muscle contraction" is in other dictionaries:
Shortening or tension of the muscles in response to irritation caused by a motor discharge. neurons. The M. s model was adopted, according to the cut, when the surface of the muscle fiber membrane is excited, the action potential first propagates through the system ... ... Biological encyclopedic dictionary
MUSCLE CONTRACTION- the main function of muscle tissue is the shortening or tension of muscles in response to irritation caused by the discharge of motor neurons. M. s. underlies all movements of the human body. Distinguish M. with. isometric, when the muscle develops an effort ... ... Psychomotor: Dictionary Reference
Contraction of a muscle at a constant tension, expressed in a decrease in its length and an increase in its cross section. In the body And. m. is not observed in its pure form. To purely I. m. the movement of an unloaded limb approaches; at… …
MUSCLES- MUSCLES. I. Histology. In general morphologically, the tissue of the contractile substance is characterized by the presence of specific differentiation in the protoplasm of its elements. fibrillar structure; the latter are spatially oriented in the direction of their contraction and ... ... Big Medical Encyclopedia
Ancient drawing of human muscles ... Wikipedia
I The shoulder joint (articulatio humeri) is a spherical joint formed by the head of the humerus and the articular cavity of the scapula. The articular surface of the scapula is surrounded by a ring of fibrous cartilage, the so-called articular lip. Through the cavity of the joint ... ... Medical Encyclopedia
The motor unit (MU) is the functional unit skeletal muscle. ME includes a group of muscle fibers and the motor neuron that innervates them. The number of muscle fibers that make up one IU varies in different muscles. For example, where ... ... Wikipedia
Muscle contraction expresses the change in the speed of muscle contraction depending on its load. Derived by the English physiologist A. V. Hill in 1938. X. formula: (P + a) (v + b) \u003d b (P0 + a), where v is the speed of muscle contraction under load ... ... Great Soviet Encyclopedia
Isotonic muscle contraction muscle contraction at a constant tension, expressed in a decrease in its length and an increase in its cross section. In the body And. m. is not observed in its pure form. To purely I. m. the movement of an unloaded limb approaches; with a gradual increase in the load until it can no longer be lifted, it is possible to observe all the transitions from I. m. to isometric muscle contraction (See Isometric Muscle Contraction).
Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what "Isotonic muscle contraction" is in other dictionaries:
Shortening or tension of the muscles in response to irritation caused by a motor discharge. neurons. The M. s model was adopted, according to the cut, when the surface of the muscle fiber membrane is excited, the action potential first propagates through the system ... ... Biological encyclopedic dictionary
MUSCLE CONTRACTION- the main function of muscle tissue is the shortening or tension of muscles in response to irritation caused by the discharge of motor neurons. M. s. underlies all movements of the human body. Distinguish M. with. isometric, when the muscle develops an effort ... ... Psychomotor: Dictionary Reference
Contraction of a muscle, expressed in an increase in its tension with a constant length (for example, contraction of a muscle of a limb, both ends of which are fixed motionless). In an organism to And. the tension developed by the muscle when trying is approaching ... ... Great Soviet Encyclopedia
The motor unit (MU) is the functional unit of skeletal muscle. ME includes a group of muscle fibers and the motor neuron that innervates them. The number of muscle fibers that make up one IU varies in different muscles. For example, where ... ... Wikipedia
HEART- HEART. Contents: I. Comparative anatomy........... 162 II. Anatomy and histology ........... 167 III. Comparative physiology .......... 183 IV. Physiology .................. 188 V. Pathophysiology ................. 207 VI. Physiology, pat. ... ... Big Medical Encyclopedia
