The biceps muscle: functions, structure. What are the arbitrary movements of the biceps muscle being regulated?

Movement of the joints of the limbs is due to the work of the muscles located on them. They consist of special fibers arranged in bundles. In the human body, there are about 400 muscles that can change the position of the body under the influence of central nervous system impulses.

Types of muscle tissue

Movement is impossible without the involvement of muscles. The total weight of such tissues in the adult body is around 30-40%. In newborn babies, it is about 20%, in the elderly it is reduced to 25-30%. But if a person keeps his activity even at an honorable age, then the muscle mass does not decrease, it remains at the same level.

Specialists distinguish different muscle groups depending on their location, functions, fiber direction. By location, these types of muscles are distinguished:

- superficial (located under the skin);

- deep;

- lateral;

- medial;

- external;

- internal.

In the form of specialists distinguish spindle-shaped, square, triangular, circular, ribbon-like muscles. By the number of heads they can be double-headed, three-headed and four-headed. Depending on the direction of the beams, they are one-birch, two-pinned, or many-pinnate.

Also, the muscles are distinguished by functions. Some provide flexion of limbs, others - flexion. Separately, spinners-lifters, squeezers (sphincter), diverting and leading muscles are distinguished.

For example, the brachial biceps muscle refers to the muscles spindle-shaped. It is attached to the bone, which is the lever, and provides a flexion of the arm at the elbow.

Shoulder bicep

The biceps arm is the anterior muscle group. It is located on the front of the humerus. This long spindle-shaped muscle has two heads. One of them is long, the second is short. They walk side-by-side, going from top to bottom. At the level of the middle part of the shoulder they join into the abdomen of a spindle-like shape.

The long head of the biceps arm muscle originates in the form of a rounded tendon in the supragastric tubercle of the shoulder blade. It passes through the shoulder joint from top to bottom. Inside, the tendon is covered by the synovial membrane. And in the area of the exit to the shoulder it passes in the intertubercular sulcus. There it is enveloped in a synovial intercampoon vagina.

The short head originates in the same place as the cranio-brachial muscle, at the apex of the crustiform process. Together they are joined in the middle of the humerus. This forms the biceps, which is supplied with blood from the axillary, lower and upper ulnar collateral, humeral and recurrent radial arteries.

In the end, there is a tendon of the biceps arm muscle, which goes to the tuberous part of the radius. The transition from the muscle to the tendon tissue passes directly over the elbow joint or near it. At the attachment point of the tendon is a two-headed bag. From its anterior-medial side there is a wide, thin dense aponeurosis. It is known under the name of Pirogov's fascia. In front he covers the ulnar fossa. This aponeurosis is woven into the fascia of the forearm.

Triceps muscle

Along the back of the humerus is the muscle, which provides extension of the arm at the elbow. It has a spindle shape. The two-headed and three-headed muscles of the shoulder differ not only in location, but in structure. The triceps has three heads: long, medial and lateral. The first of these starts on the subarctic hillock of the scapula in the form of a rounded thick sinew. Often it combines with the tendon of the widest muscle of the back. The muscular abdomen of this head passes between the round muscles (small and large) and extends to the middle part of the humerus.

The lateral head is partially covered by the deltoid muscle of the triceps. It originates on the back of the humerus. Bunches from it go down medially so that they overlap the furrow of the radial nerve.

The medial head is the shortest of the three presented. It begins with the collected bundles of muscles on the back of the humerus. A considerable part of it is covered by the lateral head. Between them and the groove of the radial nerve is the shoulder-muscular canal.

In the middle part of the posterior surface of the shoulder all three heads are joined together and form the abdomen. It ends with a thick tendon, which is attached to a special process of the ulna.

Flexion and extension in the elbow joint of the forearm is provided by the two-headed and three-headed arm muscles. Also participates in this process and the brachial muscle, called brachialysis.

Leg muscles

The posterior surface of the femur is the posterior muscular group. It includes a double-headed, semitendinous and semimembranous muscle. They all begin in the region of the ischial hillock. Their beginning is covered with a large gluteus muscle.

In this case, if semitendinosic and semimembranous muscles are located medially, then biceps occupy a lateral position. Femoral biceps stretched along the entire length of the femur, it has a spindle-shaped shape. It is adjacent to the femoral broad lateral muscle. The lateral wall of the popliteal fossa forms the femoral two-headed muscle. It can perform its functions thanks to a special structure and attachment to another bone.

It begins with two heads - long and short. At the beginning of the first one, there is a short thick tendon. It is located on the surface of the sacro-tubercle ligament and sciatic hillock. The muscle goes not strictly down, but obliquely in the lateral direction. The lower end is attached to the lower leg.

The short head of the biceps femoris begins from the posterior surface of the femur. Its lower edge ends at the tibia (shank).

Both heads are connected in the region of the border between the lower and middle parts of the femur. They become one common tendon. It passes from the back of the knee joint. This tendon is attached to the tibia (its head) and the outer part of the lateral condyle belonging to the tibia. Partly its fibers are woven into the fascia of the shin.

Functions of the biceps

Depending on what kind of work the muscles can perform, they are divided into flexors and extensors. These are the opposing groups of muscles that provide limb movement. The main flexor of the upper arm is the biceps arm muscle.

It performs the following functions:

- bends at the elbow joint arm;

- Provides the possibility of turning the brush outward;

- straining at the elbow joint arm.

The main flexor of the upper part of the leg is the biceps femoris muscle.

Foot biceps functions:

- Extension and reduction of the thigh;

- Straightening of the trunk after tilting;

- flexion in the knee joint of the shin;

- turning to the outside of the leg, bent at the knee joint;

- keeping the balance.

It is worth noting that problems with the biceps, for example its insufficient strength or flexibility, lead to pain in the back, problems with knee joints, deterioration of posture.

Extension of the upper limbs is provided by the triceps, located along the humerus. The biceps and triceps muscles can contract together or alternately. The movement of the foot in the knee joint is facilitated by the coordinated work of the biceps and four-headed muscles.

Leg extensor

The largest muscle in the human body is the quadriceps. It is located on the front of the thigh and provides an opportunity to unbend the lower limb in the region of the knee. She is also responsible for flexing the hip - approaching this part of the leg to the stomach.

Consists of a quadriceps of four bundles. Each of them is considered a separate muscle, which has its name. Separately, specialists distinguish straight, wide lateral, medial and intermediate muscles.

All of them are attached to the patella. But each of them has its own functions. For example, the straight line is responsible for flexing the hip and flexing the knee joints. But the intermediate, medial and lateral are necessary for the extension of the shin.

Providing traffic

Without the coordinated action of the muscles, it would be impossible to bend or unbend limbs. Arbitrary movements of the biceps are regulated by the spinal cord. This becomes possible due to the alternation of the processes of inhibition and excitation that pass in the spinal cord. The muscles responsible for flexion and extension of the limbs can be simultaneously relaxed. This happens, for example, at a time when the hand is relaxed hanging along the body.

Their reduction is due to the activity of neurons of the spinal cord responsible for movement. The process of relaxation is associated with the inhibition of these cells of the nervous system. If a man in a straight arm holds a dumbbell, then the two-headed and three-headed muscles will work simultaneously.

At the arrival of nerve impulses, the muscle receives a certain command, depending on this, the process of relaxation or muscle tension begins. When cutting, it affects the bone to which it is attached, like a lever.

The principle of the functioning of muscles

Reducing any muscle group is a work that requires energy to perform. Its source can be the products released during the decomposition and oxidation of various organic substances. In muscle fibers, they are exposed to various chemical reactions by the action of oxygen. The result of this interaction is the release of energy. This is accompanied by the formation of cleavage products - carbon dioxide and water.

With too much strain on the muscles, the natural process of fatigue begins. This is accompanied by a decrease in their performance. After rest, everything is restored.

It was noted that when performing rhythmic exercises, fatigue comes somewhat later. After all, in the intervals between contractions, muscles partially have time to rest and recover. But the workload is affected by the intensity of the load. The higher it is, the faster will fatigue.

Work of the central nervous system

In making this or that movement, a person does not think. He does everything automatically. But thus each motor act for nervous system is the difficult process for which performance it is necessary to involve its various levels. All active movements are controlled by the brain. They are called arbitrary or conscious.

Before the contraction of muscle begins, the cerebral cortex, through special channels, receives information about the state of the joint-muscle fibers. She estimates how ready they are for the load. Therefore, it can not be said that the arbitrary movements of the biceps muscle are regulated solely by the spinal cord. After all, the bark controls the strength, consistency and duration of each of the contractions.

The motor centers are located in the frontal part of the brain of the cerebral cortex. It is in the fore departments that all signals are integrated. After this, the model of the future movement is formed.

In order for an arbitrary contraction of muscles to occur, the impulses formed in the cortical part of the brain must reach the corresponding muscles. They pass on a special path, which experts call cortical and muscular. Arbitrary movements of the biceps are regulated by the central and peripheral neurons. The first of these are the bodies of pyramidal cells with axons. The second is the cells of the spinal cord.

Neurons bind part of the cerebral cortex responsible for movement, special sections of the spinal cord and brain stem. This whole complex is called a pyramidal system.

Possible problems

Sometimes, when some part of the cortico-muscle path is affected. In this case, the muscles do not receive a signal coming from the cortex of the brain. Their arbitrary movements become impossible.

For example, with a partial lesion, the biceps muscle can not perform its functions in full. Depending on the site of the lesion, problems can occur in different parts of the body. Partial damage, as a rule, leads to paresis.

With such damages, arbitrary movements of the biceps are also regulated by the brain and spinal cord. But due to disruption of communications, it is possible to violate, restrict the intensity and force of contractions. Problems can be central or peripheral, depending on which neurons are affected.

Examination of such patients should be thorough. During its carrying out it is important to determine not only how the motor function was preserved, but also check the presence of muscle atrophy. They also look at the deformities of the chest, spine, and minor twitchings of the muscles.

But, it is worth noting that not always because of problems with the cortical and muscular path becomes impossible movements. For example, with the pathology of the joint apparatus, violations of proprioceptive sensitivity, the biceps arm muscle can stop working. Functions it will not perform in full and in the event that there were cicatrical changes in muscles. Therefore, it is important to determine the cause, because of which it became impossible to contract the muscles. For this purpose, they examine how the patient can perform active and passive movements, and evaluate his reflexes.