Humans and the rest of the living beings on Earth navigate in a three-dimensional environment and, therefore, we require a powerful skeletal and muscular system that allows us to respond to external stimuli and overcome the force of gravity, among many other things. .
It is interesting to know that it is estimated that there are more than 650 types of muscles in the human body (according to the established definition) and that a process as seemingly simple as smiling involves a total of 20 facial muscle structures to be carried out.
It is clear that we cannot live without a correct muscular system due to the psychomotor importance it harbors and, therefore, diseases such as Duchenne dystrophy (which progressively weaken this system) have a long-term survival rate of approximately 10%. Without proper functioning of muscle tissue, vital tasks such as breathing and blood circulation can be severely compromised.
With this data we wanted to show the very important functionality of this device, but there are many more terms and particularities locked in each of our muscles and tendons. Stay with us, because in the following lines we will tell you everything you need to know about the muscular system.
From a physiological point of view, the muscular system can be defined as the set of muscles (more than 600) that exist in the human body This device stabilizes the body position in three-dimensional space, produces the movement of bone structures, regulates the volume of organs, mobilizes substances within our body and plays an essential role in the production of heat, among many other things.
First of all, we must highlight that there is a clear disagreement between various bibliographic sources, since certain experts include within this system all tissue of a muscular nature, while other sources include in this definition only the muscles that can be controlled voluntarily. by a living organism (skeletal muscles). For informative reasons, we focus our attention on the broadest and most friendly definition of the term.
According to clinical sources, A muscle can be defined as a tissue made up of muscle fibers endowed with a contractile capacity
In general, we can summarize that the basic and general physiological properties of all muscle tissue are contractility, excitability, extensibility and elasticity All this allows the biomechanical action of living beings and other processes as basic as the heartbeat or breathing.
Types of muscle groups
As we have said, if we take into account the muscle tissues that are part of the organs, we can observe 3 different types of them. We will tell you about them in the following lines.
1. Smooth muscle
It is described as visceral or involuntary. It forms the walls of hollow viscera, such as the stomach and bladder, and those of various tubular ducts such as the different units of the circulatory system, the respiratory system, the digestive tract, the respiratory system and the reproductive organs, for example.
Generally, smooth muscles cannot be controlled at the will of the individual, but they are automatically at the mercy of the nervous system. They contract slowly, are more extensible and capable of maintaining a state for a longer time, that is, they do not “tire” as easily as striated muscles.
2. Striated or skeletal muscle
According to certain authors, only this type of muscles would form the muscular system per se. Unlike smooth muscle, The striatum is what gives shape to the body and is attached to the bones, mainly on the legs, arms, abdomen, chest, neck and face. These muscles are called “striated” because they are made up of alternating bands of light and dark tones.
These muscle fibers are innervated by the cranial or spinal nerves and, as we have previously said, are limited to the voluntary government of the individual. They can contract quickly and energetically, but they “tire” quickly and therefore they must rest between periods of great effort.
As its name suggests, the cardiac muscle is located in the heart. As you can imagine, Due to its functionality, it is not under the control of individual will, which is why it is considered automatic This type of muscle tissue has four basic properties:
Muscle nomenclature
It is interesting to know that muscles can be classified in a very extensive terminological chain according to multiple parameters. For example, based on its function, a muscle can be a supinator, pronator, adductor, levator and tensor. According to their shape, they are classified in terms such as triangular, square, pyramidal, rhomboid and trapezoid.
Other classification criteria that we are not going to investigate are according to the size, the bone relationship, the direction of the fibers, the number of insertions or the topographic relationship. To give you a general idea, There are more than 30 muscle types based on each and every one of the parameters described
The mechanism of muscle contraction
Everything we have explained so far is really interesting, but how does it translate from a functional point of view? In the following lines we explain, in general terms, the mechanism of muscle contraction.
First of all, An action potential travels along a motor nerve to the end of the nerve, which empties into muscle fibers The signal comes from the brain which, through electrical impulses transported through neurons and the release of neurotransmitters (synapses), communicates the signal to the muscle that it must carry out the action for which it is prepared.
At each end of the nerve, it releases a very special neurotransmitter: acetylcholine. In short, we will say that acetylcholine allows the opening of sodium channels in muscle fibers and that, indeed, the sudden concentration of this ion causes an action potential that stimulates muscle cells to release calcium. The release of calcium allows the reconfiguration of the fibers of actin and myosin, globular proteins essential for this tissue that, with the expenditure of ATP, generate the typical movement of muscle contraction
Once this has been described, we must also note that there are two main types of contractions:
Functions of the muscular system
We have already covered the main structures of the muscular system and its method of action but, in these last lines, we find it of special interest to elucidate the functionality of the muscular system Among them, we find the following:
In general, if we consider the muscular system in its strictest sense (only the striated or skeletal muscles), we could say that Its main function is only the production of voluntary movements in the body in response to some type of environmental stimulus On the other hand, if we take into account all tissue of a muscular nature, its functionality extends to the very conception of life, since without the muscles of the heart the blood would not beat and we would simply not exist.
Summary
Compressing the particularities of the muscular system in a few lines is a real challenge, since each small bundle, each fiber and each globular protein included here provides enough information to write a book on its own. In any case, we have given you a general overview of this system, from the typology of its tissues to its functionality, including the mechanism of action at a chemical level.
If we want you to stay with one idea, this is the following: in its most closed sense, the muscular system is one that is made up of voluntary muscles, that is, of a skeletal nature. In a broader sense, this apparatus is made up of more than 600 types of muscles, which range from the tissues that are attached to the bones to those that form the various organs essential for survival.
