Muscle contraction is a physiological process that muscles develop by shortening or stretching depending on tension.
A muscle contraction is a physiological process developed by muscles when, depending on the tension, they stretch or shorten. This process is controlled by the central nervous system and allows the production of motor force.
From the Latin contractĭo , contraction is the action and effect of contracting or contracting . The term can refer to the reduction to a smaller size, the acquisition of a habit, illness or vice, and the celebration of marriage.
Muscular , on the other hand, is that belonging to or relating to muscles . We can establish that muscular also has its etymological origin in Latin since the term is made up of three parts of that aforementioned language: mus , which is synonymous with “mouse” ; culus , which is equivalent to “small” ; and finally the suffix -ar , which can be translated as “relative to” .
Muscles and muscle contraction
Muscles are organs made up of contractile fibers (known as muscle fibers ) that can be linked to the skeleton ( skeletal muscles ) or be part of the structure of other organs or apparatus ( visceral muscles ).
Thanks to motor force, upper muscles can move the contents of a cavity they cover (what smooth muscles do), move the organism through the environment or mobilize other objects ( striated muscles ).
Possible modifications or alterations
In addition to all of the above, it is important that we know that there are situations that generate modifications or alterations in muscle contraction. Specifically, among the most significant situations of this type are the following:
- Rigor mortis . This term is used to refer to the stiffness experienced by the muscles of a person who has died. Specifically, they will become absolutely rigid between three and four hours after the individual has died and will remain that way for an entire day.
- muscle atrophy . Not exercising the muscles, as happens for example to patients who spend a lot of time in bed, is the main reason that generates this aforementioned situation, which basically consists of the muscle not only decreasing its size but also its strength.
Muscle contraction can be classified in different ways.
Classification of muscle contractions
It is possible to distinguish between voluntary contractions (controlled by the brain ) and involuntary reflexes (which depend on the spinal cord). The striated muscles contract voluntarily from a conscious effort originating in the brain. Brain signals are directed through the nerves to the motor neuron that stimulates the muscle fiber. Involuntary muscle contractions, on the other hand, originate in the spinal cord through a circuit with gray matter .
Another classification of muscle contractions allows us to refer to isotonic contractions (when muscle fibers contract and modify their length), concentric contractions (the muscle shortens and mobilizes a part of the body to overcome resistance) and isometric contractions ( the muscle remains static but generates tension), among others.
Specifically, we would have to establish that within isotonic contractions, of equal tension, there are two clearly differentiated types: the concentric ones, which we have already explained, and then there are the eccentric ones, which are defined by the fact that in them what the muscle is lengthening. This latter situation occurs because the resistance is greater than the tension exerted by the muscle itself.