Muscle

The muscles are a contractile form fabrics of the animals. They form one of the four major types of fabrics, the others being the epithelial fabric , the conjunctive Tissu, the nervous Tissu. The muscular Contraction makes it possible to drive parts of the body, or to drive substances inside the body.

The science of the muscle is the Myologie but the latter is interested above all in the skeletal striated muscle.

Types

The human body includes/understands more than 639 muscles whose size varies according to their function. These muscles constitute on average 40% of the dry weight of the body.

One distinguishes the striated muscles and the smooth muscles:

  • the striated muscles (named thus according to their microscopic aspect ) are under control of the central nervous system (voluntary system). They link in general Os between them ( muscles of the skeleton ): they allow the Motricité.

  • the Myocarde (the Heart) is a particular case, because although this muscle is striated (microscopically speaking), it is provided with a clean system of contractions, sensitive to hormonal stimulations, and it is difficult to control it consciously.

The striated muscles with the skeleton are equipped with fibers with two types (the proportion being variable according to the muscles, and under control Génétique):

  • the fibers " lentes" (type I or “red”), more effective in aerobic metabolism (particularly rich in myoglobin and mitochondries). They are the fibers of the endurance.
  • the fibers " rapides" (IIa type), more effective in anaerobic metabolism. Producing more power during short impulses, they are more sensitive to tiredness. This one are bulkiest. This is why the bodybuilders involve mainly fast fibers and reciprocally a sprinter has a great muscular volume.
  • There exists between the two an intermediary which is IIb; according to the genetics of the person and the type of preparation or physical framing of the person during her development, these fibers will become types I or standard IIa.

The muscular cell

The Myocyte is the basic muscular cell. It is a cell longiligne which comprises contractile fibers made up of polymers of Protéine S of the cytosquelette: the Actine and the Myosine. The phenomenon of contraction corresponds to a slip of these two elements and results in a shortening from muscle fiber. To note that if these two proteins are present in all the cells of the organization, it is the particular fitting of fibers of actine and of myosine in the myocytes which confers this tissue specificity.

The myocytes of the type I (slow muscle, aerobic cells) are very rich in Mitochondrie S which bring energy necessary to the contraction in the form of ATP. They are also rich in Myoglobine, able to fix oxygen more strongly than the Hémoglobine, and which gives them a characteristic red color.

The myocytes of the type II (fast muscle, anaerobic cells) are lower in Mitochondrie S and Myoglobine. They are on the other hand much richer in glycogen and enzyme glycolytic from where a white color.

When the oxygen reserves fixed by the myoglobin are exhausted (what takes largely less than one second), and that the flow of blood and thus of oxygen did not adapt yet to the request (what takes several seconds, and even several minutes to reach the maximum flow) the cell produces ATP in absence of oxygen, initially by consuming part of its stock of phosphocréatine (PCr), then by glycolysis. The latter gives place to the production of Lactic acid (or lactate). The power is higher but the output is less. Once the adapted blood provisioning, the cell goes back in aerobic mode: the power is less, but the lactic acid is consumed and the general output is better.

The myoblastes are the cells precursors of the muscles. During gestation then childhood or a cure following a lesion, these cells divide and amalgamate between them to form myotubes. They are long and plurinucléées cells (several cores). The myotubes synthesize then contractile proteins (actine and myosine) and are transformed into myocytes. The myocytes are more or less long according to the muscle (they can reach 35 cm length) and have a diameter from 10 to 100 micrometers. The cores are pushed back with the periphery of the cell and the majority of the cytoplasm is occupied by contractile proteins and the reticulum sarcoplasmic. The myocytes cannot divide but grow by increasing the volume of the cytoplasm. In an adult muscle the number of myoblastes (or cells satellite) is limited, they do not play any more but one part of repair of the myocytes injured following efforts of unusual intensity or duration.

The myocytes contract in answer to a nervous stimulation. This one in the case of causes the depolarization of the plasmic membrane, called sarcolemme the muscle. The signal is propagated along the sarcolemme. Depolarization involves an activation of receiver DHP. The receiver of DHP by conformational change, couples with the receiver of ryanodine reticulum sarcoplasmic. The receiver of ryanodine releases then from calcium, towards the cytoplasm since the calcic gradient of concentration is favorable there. In fact the ions calciums start the contraction itself while being fixed on contractile proteins. The repompage of the ions calcium in the reticulum sarcoplasmic causes relieving. The whole of these phenomena is called the coupling excitation-contraction. source international of UNESCO

Some of the striated muscles with the human body

Muscles according to their form

Muscles according to their function:

Anatomy

The muscles present varied forms which one can bring back to three:
  1. long muscles in spindle : these are spindle-shaped muscles of which the length is prevalent. Their body is reinflated and they are finished by hard and white cords: the tendons which fix them at the bones. Certain muscles carry to the one their ends 2,3 or 4 tendons (biceps, triceps,…).
  2. broad and flat muscles : they are flat, out of blade or ribbon. Spread out in range but without tendon, they fit on the bones by a called tendineuse blade aponévrose of insertion. They form the walls of the large cavities of the body: the large pectoral one, the diaphragm.
  3. short muscles : they are circular, delimiting an opening. There are like example of short muscles the orbicular muscles (orbicular of the lips). They are annular, surrounding a hollow internal organ; they are called then sphincters , and they open following a pressure.

Physiology

The good performance of the muscles requires the contribution of energy and water to convey toxins and to keep muscular volume. This energy comes from our daily food (as much by straight feedingstuffs, such lipids, glucids and proteins, but also thanks to salts and minerals) which undergoes various chemical conversions gathered under the term of Métabolisme.

See also muscular Contraction.

Control nervous

It is the central nervous system which coordinates the action of the muscles. Examples:

  • the movement of inflection : if one brings the front armlever closer to the arm, the biceps is contracted while the triceps is slackened

  • the movement of extension : if one moves away the front armlever from the arm, the triceps is contracted while the biceps is slackened.

Role in health and the diseases

Exercise

The Exercice is often recommended like means of improving the driving capacities, the Agilité and the muscular force. The exercise has various effects on the conjunctive muscles, fabrics, the Os, and the Nerf S which stimulate the muscles.

Diseases

  • Turbid neuromusculaires

Spasticity gold Paralysis, depending one the natural hiring and off the problem. With broad proportion off neurological disorders leads to problems with movement, ranging from Cerebrovascular accident (stroke) and Parkinson' S disease to Creutzfeldt-Jakob disease. --> antibodies to the Acetylcholine receptor, and its related condition Lambert-Eaton myasthenic syndrome (LEMS). Tetanus and Botulism are bacterial infections in which bacterial toxins causes increased gold decreased muscle thunders, respectively. -->

  • the Myopathie S are all the diseases which affect the muscle itself, rather than its nervous control.

  • the muscular dystrophies are a great group of diseases, for the majority hereditary, where the integrity of the muscle is compromised. That involves a progressive loss of force, a high dependence and a shortened life.

  • Turbid muscular inflammatory:

Prednisolone).
    • Polymyositis, Dermatomyositis and Autoimmune Inclusion-body myositis are conditions in which the muscle is affected. -->
Myoglobin thus released may causes renal Acute failure. --> Tumor S off muscle include:
  • Smooth muscle: Leiomyoma (benign, very common in the Uterus), Leiomyosarcoma (malignant, very rare)
  • Striated muscle: Rhabdomyoma (benign) and Rhabdomyosarcoma (malignant) - both very rare
  • Metastasis from elsewhere (e.g Lung cancer)-->

Asthma), the Digestive system (e.g Irritable bowel syndrome) and the Urinary leaflet (e.g Urinary incontinence). Thesis disease processes are not usually confined to the muscular tissue. -->

Random links:Niort chamois Football Club | Mother (Yvelines) | University Saint-Raphaël Life-Health | Coulonvillers | Channel of Roanne with Digoin