Muscles are one of the main components of the body. They are based on tissue whose fibers contract under the influence of nerve impulses, which allows the body to move and stay in the environment.
Muscles are located in every part of our body. And even if we do not know about their existence, they are still there. It’s enough, for example, to go to the gym for the first time or to do aerobics - the next day even those muscles that you didn’t know about would be sore.
They are responsible not only for movement. At rest, the muscles also require energy to keep themselves in good shape. This is necessary so that at any moment a certain part of the body can respond to a nerve impulse with the appropriate movement, and not waste time preparing.
To understand how the muscles are arranged, we suggest recalling the basics, repeating the classification and looking into the cellular structure of the muscles. We also learn about diseases that can impair their performance and how to strengthen skeletal muscle.
General concepts
According to their filling and ongoing reactions, muscle fibers are divided into:
Skeletal muscles are elongated tubular structures, the number of nuclei in one cell of which can reach several hundred. They consist of muscle tissue, which is attached to various parts of the bone skeleton. Contraction of striated muscles contribute to human movements.
Varieties of forms
How do muscles differ? The photos presented in our article will help us figure this out.
Skeletal muscle is one of the main components of the musculoskeletal system. They allow you to move and maintain balance, and are also involved in the process of breathing, voice formation and other functions.
The human body has more than 600 muscles. In percentage terms, their total weight is 40% of the total body weight. Muscles are classified by shape and structure:
- thick spindle-shaped;
- thin lamellar.
Classification makes learning easier
The division of skeletal muscles into groups is carried out depending on the location and their importance in the activity of various organs of the body. The main groups:
Muscles of the head and neck:
- facial expressions - are used when smiling, communicating and creating various grimaces, while ensuring the movement of the components of the face;
- chewing - contribute to a change in the position of the maxillofacial department;
- arbitrary muscles of the internal organs of the head (soft palate, tongue, eyes, middle ear).
Skeletal muscle groups of the cervical region:
- superficial - contribute to inclined and rotational movements of the head;
- medium - create the lower wall of the oral cavity and contribute to the downward movement of the jaw, hyoid bone and laryngeal cartilage;
- the deep ones tilt and rotate the head, create the raising of the first and second ribs.
The muscles, the photos of which you see here, are responsible for the body and are divided into muscle bundles of the following departments:
- chest - activates the upper part of the torso and arms, and also contributes to a change in the position of the ribs during breathing;
- abdomen - gives the movement of blood through the veins, changes the position of the chest during breathing, affects the functioning of the intestinal tract, promotes bending of the body;
- dorsal - creates the motor system of the upper limbs.
Muscles of the extremities:
- upper - consist of muscle tissue of the shoulder girdle and free upper limb, help move the hand in the shoulder joint bag and create movements of the wrist and fingers;
- lower - play a major role in the movement of a person in space, are divided into the muscles of the pelvic girdle and the free part.
Skeletal muscle structure
In its structure, it has a huge amount of muscle fibers of oblong shape with a diameter of 10 to 100 microns, their length varies from 1 to 12 cm. Fibers (microfibrils) are thin - actin, and thick - myosin.
The first consists of a protein having a fibrillar structure. It is called actin. Thick fibers are made up of various types of myosin. They differ in the time required for the decomposition of the ATP molecule, which leads to different contractions.
Myosin in smooth muscle cells is in a dispersed state, although there is a large amount of protein, which, in turn, is significant in prolonged tonic contraction.
The structure of the skeletal muscle is similar to a rope woven from fibers or a stranded wire. Above it is surrounded by a thin cover made of connective tissue, called epimysium. From its inner surface, deeper branches of the connective tissue, creating septa, extend deep into the muscles. They wrapped individual bundles of muscle tissue that contain up to 100 fibrils in each. Narrower branches depart from them even deeper.
Through all layers, the circulatory and nervous systems penetrate into skeletal muscles. The arterial vein runs along the perimisium - it is the connective tissue that covers the bundles of muscle fibers. Arterial and venous capillaries are located nearby.
Development process
Skeletal muscles develop from the mesoderm. From the side of the nerve groove, somites form. After the passage of time, myotomas are released in them. Their cells, acquiring the shape of a spindle, evolve into myoblasts, which divide. Some of them progress, while others remain unchanged and form myosatellite cells.
An insignificant part of myoblasts, due to the contact of the poles, creates contact with each other, then they break up in the contact zone of the plasmalemma. Thanks to cell fusion, symplasts are created. Undifferentiated young muscle cells that are in the same environment as the myosymplast of the basement membrane migrate to them.
Skeletal muscle function
This musculature is the basis of the musculoskeletal system. If it is strong, the body is easier to maintain in the right position, and the likelihood of stoop or scoliosis is minimized. Everyone knows about the advantages of playing sports, so let's look at the role that muscles play in this.
The contractile tissue of skeletal muscles in the human body performs many different functions that are necessary for the proper location of the body and the interaction of its individual parts with each other.
Muscles perform the following functions:
- create body mobility;
- protect the thermal energy created inside the body;
- facilitate movement and vertical retention in space;
- Contribute to shortening the airways and help with swallowing
- form facial expressions;
- contribute to heat production.
Ongoing support
When muscle tissue is at rest, there is always a slight tension in it called muscle tone. It is formed due to insignificant impulse frequencies that enter the muscles from the spinal cord. Their action is determined by signals penetrating from the head to the spinal motor neurons. Muscle tone also depends on their general condition:
- stretching;
- level of filling of muscle cases;
- blood enrichment;
- total water and salt balance.
A person has the ability to regulate the level of muscle load. As a result of prolonged physical exercise or strong emotional and nervous overstrain, muscle tone increases involuntarily.
Skeletal muscle contractions and their varieties
This function is basic. But even it, with apparent simplicity, can be divided into several types.
Types of contractile muscles:
- isotonic - the ability of muscle tissue to shorten without changing muscle fibers;
- isometric - during the reaction, the fiber contracts, but its length remains the same;
- auxotonic - the process of contraction of muscle tissue, where the length and tension of the muscles undergo changes.
Consider this process in more detail.
First, the brain sends an impulse through the system of neurons, which reaches the motor neuron adjacent to the muscle bundle. Next, the efferent neuron is innervated from the synoptic vesicle, and the neurotransmitter is secreted. It connects to receptors on the sarcolemma of muscle fiber and opens the sodium channel, which leads to depolarization of the membrane, causing an action potential. With a sufficient amount, the neurotransmitter stimulates the production of calcium ions. Then it combines with troponin and stimulates its contraction. He, in turn, delays tropomeazin, allowing actin to combine with myosin.
Next, the actin filament glides relative to the myosin filament, resulting in a reduction in skeletal muscle. To understand the process of compression of striated muscle bundles, a schematic image will help.
The principle of skeletal muscle
The interaction of a large number of muscle bundles contributes to various body movements.
Skeletal muscle function can occur in the following ways:
- synergist muscles work in one direction;
- muscle antagonists contribute to performing opposing movements to exert tension.
The antagonistic effect of muscles is one of the main factors in the activity of the musculoskeletal system. When carrying out any action, not only the muscle fibers that perform it, but also their antagonists are included in the work. They contribute to counteraction and give the movement specificity and grace.
The striated skeletal muscle, when exposed to the joint, does a difficult job. Its nature is determined by the location of the axis of the joint and the relative position of the muscle.
Some skeletal muscle functions are poorly illuminated, and are often not talked about. For example, some of the bundles act as a lever for the work of the bones of the skeleton.
Muscle work at the cellular level
The action of skeletal muscles is due to two proteins: actin and myosin. These components have the ability to move relative to each other.
For the performance of muscle tissue, it is necessary to expend energy contained in the chemical bonds of organic compounds. The breakdown and oxidation of such substances occurs in the muscles. There is always air here, and energy is released, 33% of all this is spent on the performance of muscle tissue, and 67% is transferred to other tissues and spent on maintaining a constant body temperature.
Musculoskeletal diseases of the skeleton
In most cases, deviations from the norm during muscle functioning are due to the pathological condition of the responsible parts of the nervous system.
The most common skeletal muscle pathologies:
- Muscle cramps - a violation of the electrolyte balance in the extracellular fluid surrounding the muscle and nerve fibers, as well as changes in the osmotic pressure in it, especially its increase.
- Hypocalcemic tetany - involuntary tetanic contractions of skeletal muscles observed with a drop in extracellular Ca2 + concentration to about 40% of the normal level.
- Muscular dystrophy is characterized by progressive degeneration of skeletal muscle and myocardial fibers, as well as muscle disability, which can lead to death due to respiratory or heart failure.
- Myasthenia gravis is a chronic autoimmune disease in which antibodies to the nicotinic ACh receptor are formed in the body.
Skeletal muscle relaxation and recovery
Proper nutrition, lifestyle and regular training will help you become the owner of healthy and beautiful skeletal muscles. It is not necessary to do weightlifting and build muscle. Enough regular cardio and yoga.
Do not forget about the mandatory intake of necessary vitamins and minerals, as well as regular visits to saunas and baths with brooms, which allow you to enrich muscle tissue and blood vessels with oxygen.
Systematic relaxing massages will increase the elasticity and reproduction of muscle bundles. Also, a visit to the cryosauna has a positive effect on the structure and functioning of skeletal muscles.