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 hold in the environment.
Muscles are located in every part of our body. And even if we don't know they exist, they still exist. It is enough, for example, to go to the gym for the first time or do aerobics - the next day you will start to hurt even those muscles that you did not even know you had.
They are responsible for more than just movement. At rest, 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 muscles work, we suggest remembering the basics, repeating the classification and looking into the cellular structure of muscles. We will also learn about diseases that can impair their performance and how to strengthen skeletal muscles.
General concepts
According to their content and reactions, muscle fibers are divided into:
- striped;
- smooth.
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. The contractions of the striated muscles contribute to human movement.
Varieties of forms
How are muscles different? The photos presented in our article will help us figure this out.
Skeletal muscles are 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 production and other functions.
There are over 600 muscles in the human body. As a percentage, their total weight is 40% of the total body weight. Muscles are classified by shape and structure:
- thick fusiform;
- thin lamellar.
Classification makes learning easier
The division of skeletal muscles into groups is carried out depending on their location and their importance in the activity of various organs of the body. Main groups:
Muscles of the head and neck:
- mimic - are used when smiling, communicating and creating various grimaces, while ensuring the movement of the constituent parts of the face;
- chewing - contribute to a change in the position of the maxillofacial region;
- voluntary muscles of the internal organs of the head (soft palate, tongue, eyes, middle ear).
Cervical skeletal muscle groups:
- superficial - contribute to oblique androtational movements of the head;
- medium - create the lower wall of the oral cavity and promote downward movement of the jaw, hyoid bone and laryngeal cartilage;
- deep carry out tilts and turns of the head, create a rise in the first and second ribs.
The muscles, the photos of which you see here, are responsible for the torso and are divided into muscle bundles of the following departments:
- thoracic - activates the upper torso and arms, and also helps to change the position of the ribs during breathing;
- abdominal region - gives the movement of blood through the veins, changes the position of the chest during breathing, affects the functioning of the intestinal tract, promotes flexion of the body;
- dorsal - creates the motor system of the upper limbs.
Limb muscles:
- upper - consist of the muscle tissue of the shoulder girdle and the free upper limb, help move the arm in the shoulder joint bag and create wrist and finger movements;
- lower - play the main 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 number of oblong muscle fibers 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 former consist of a protein having a fibrillar structure. It's called actin. Thick fibers are made up of various typesmyosin. They differ in the time it takes for the decomposition of the ATP molecule, which causes different contraction rates.
Myosin in smooth muscle cells is in a dispersed state, although there is a large amount of protein, which, in turn, is meaningful in a prolonged tonic contraction.
The structure of the skeletal muscle is similar to a rope woven from fibers or a stranded wire. From above it is surrounded by a thin sheath of connective tissue called the epimysium. Thinner ramifications of the connective tissue extend from its inner surface deep into the muscle, creating partitions. They "wrapped" individual bundles of muscle tissue, which contain up to 100 fibrils in each. Narrower branches extend even deeper from them.
Through all layers, the circulatory and nervous systems penetrate into the skeletal muscles. The arterial vein runs along the perimysium - this is the connective tissue that covers the bundles of muscle fibers. Arterial and venous capillaries are located side by side.
Development process
Skeletal muscles develop from the mesoderm. From the side of the neural groove, somites are formed. After a while, myotomes 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 myosatellitocytes.
An insignificant part of the myoblasts, due to the contact of the poles, creates contact with each other, then in the contact zone the plasma membranes disintegrate. Cell fusion creates symplasts. Undifferentiated young muscle cells migrate to them, which are in the same environment as the basement membrane myosymplast.
Skeletal Muscle Functions
This muscle is the basis of the musculoskeletal system. If it is strong, the body is easier to maintain in the desired position, and the likelihood of stooping or scoliosis is minimized. Everyone knows about the benefits of playing sports, so let's look at the role that muscles play in this.
The contractile tissue of skeletal muscles performs many different functions in the human body that are necessary for the correct positioning of the body and the interaction of its individual parts with each other.
Muscles perform the following functions:
- create body mobility;
- save the thermal energy created inside the body;
- promote movement and vertical retention in space;
- contract the airways and help with swallowing;
- shape facial expressions;
- contribute to heat production.
Continuous 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 dorsal motor neurons. Muscle tone also depends on their general condition:
- stretching;
- filling level of muscle cases;
- blood enrichment;
- general water and s alt 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 strain, muscle tone involuntarily increases.
Skeletal muscle contractions and their varieties
This function is the main one. But even she, with seeming 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 are subject to changes.
Let's take a closer look at this process
First, the brain sends an impulse through the system of neurons, which reaches the motoneuron adjacent to the muscle bundle. Further, the efferent neuron is innervated from the synoptic vesicle, and the neurotransmitter is released. It binds to receptors on the sarcolemma of the muscle fiber and opens the sodium channel, which leads to membrane depolarization, which triggers an action potential. With sufficient amounts, the neurotransmitter stimulates the production of calcium ions. It then binds to troponin and stimulates its contraction. This in turn retracts tropomeasin, allowing actin to bind to myosin.
Next, the process of sliding of the actin filament relative to the myosin filament begins, as a result of which thecontraction of skeletal muscles. A schematic representation will help to understand the process of compression of striated muscle bundles.
How skeletal muscles work
The interaction of a large number of muscle bundles contributes to various movements of the torso.
Skeletal muscles can work in the following ways:
- muscle-synergists work in one direction;
- Antagonist muscles promote opposite movements to exercise tension.
Antagonistic action of muscles is one of the main factors in the activity of the musculoskeletal system. When performing any action, not only the muscle fibers that perform it, but also their antagonists are included in the work. They promote counteraction and give the movement concreteness and grace.
Striated skeletal muscle, when exposed to a joint, performs complex work. Its character is determined by the location of the axis of the joint and the relative position of the muscle.
Some skeletal muscle functions are under-reported and 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 carried out by two proteins: actin and myosin. These components have the ability to move relative to each other.
For the implementation of the performance of muscle tissue, the consumption of energy contained in the chemical bonds of organicconnections. The breakdown and oxidation of such substances occur in the muscles. Air is always present 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 is spent on maintaining a constant body temperature.
Diseases of the musculature of the skeleton
In most cases, deviations from the norm in the functioning of the muscles are due to the pathological condition of the responsible parts of the nervous system.
Most common skeletal muscle pathologies:
- Muscle cramps - an electrolyte imbalance in the extracellular fluid surrounding muscle and nerve fibers, as well as changes in osmotic pressure in it, especially its increase.
- Hypocalcemic tetany is an involuntary tetanic contraction of skeletal muscle that occurs when extracellular Ca2+ levels fall to about 40% of normal levels.
- Muscular dystrophy is characterized by progressive degeneration of skeletal muscle fibers and myocardium, as well as muscle disability, which can be fatal 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.
Relaxation and recovery of skeletal muscles
Proper nutrition, lifestyle and regular exercise will help you become the owner of he althy and beautiful skeletal muscles. It is not necessary to do weightlifting and build muscle mass. Enough regularcardio and yoga classes.
Do not forget about the mandatory intake of essential 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.
