Muscle tone is the inherent tension of muscular apparatus. Even at rest, muscles exhibit some inherent tension and resistance to external stimuli, also known as resting tone. Disturbances in muscle tone manifest themselves as either decreased or increased tension.
What is muscle tone?
Muscle tone is the inherent tension of muscular apparatus. Even at rest, muscles exhibit some degree of inherent tension. The muscles of the body exhibit a degree of tension. This degree of tension is also known as tonus or muscle tone. The tension is caused by the viscoelastic properties of the tissues and stimuli from the central nervous system. Even at rest, muscles have a certain degree of tone, also known as resting or basal muscle tone. Medicine distinguishes passive muscle tone from active muscle tone. Passive muscle tone is determined by material properties, anatomical tissue structures, muscle fiber composition and anatomical location. In addition, the filling state of extracellular and intracellular fluid cavities also influence passive tone. The same applies to blood flow and oxygen supply as well as temperature, the type of stress and the degree of fatigue of the muscle. Neurophysiologically, muscle tone usually refers to active tone. Unlike passive tone, active size is determined by the innervation of the muscles and the sensorimotor program. Prolonged and painful muscle tone is also called tension. Reflex tone, on the other hand, is understood by neurologists as an involuntary tension within the framework of motor units.
Function and task
Skeletal muscle tone is produced by the successive contractions of individual muscle fibers. The alternating contraction movements allow a certain level of tension to be maintained even at rest. The smooth muscle cells, on the other hand, contract permanently and thus generate muscle tone. Resting tone refers to the force with which a muscle opposes an applied force. It is not due to the muscles themselves, but is controlled by afferent and efferent fibers of the reflex arches on the muscle. These reflex arcs are neural processes that trigger a body reflex – in this case, tension. Skeletal muscles with their muscle tone are the active part of the musculoskeletal system. This musculature is capable of contraction and relaxation and thus makes movements conceivable in the first place. It is only through muscle tone that humans are capable of locomotion. Without muscle tone, a person would not even be able to maintain their own posture without effort. Neither standing nor sitting would be possible for the person. Muscle tone also plays a special role in coordinated and fine motor movements. In order for the musculature to perform its many tasks and maintain the muscle tone required to do so, it needs a lot of energy. In terms of the body’s energy balance, even the basic muscle tone accounts for around a quarter of the total energy requirement. During active movements, the energy requirement increases even more. Dieters and athletes know this connection. The more muscle mass a person has, the more calories he burns even at rest. This phenomenon is related to the basic muscle tone of each muscular system. The more muscles, the higher therefore also the energy conversion. Muscle building is therefore part of the standard program for those who want to lose weight. Among other things, heat is produced as a by-product of the energy metabolism of the muscles. In this context, the basic muscle tone even plays an important role in maintaining its own body heat.
Diseases and ailments
A disturbed muscle tone is also called muscular dystonia by neurologists. Such dystonia of the muscle can manifest itself as increased tension, but also as decreased tone. A completely lost tone is present, for example, in paralysis. This clinical picture is also called flaccid [[paralysis|paralysis. All motor nerves of a body part are out of action in flaccid paralysis. To be distinguished from this is paresis. This is also a paralytic phenomenon. However, this phenomenon is not accompanied by a complete failure, but by a partial failure of the motor nerves of certain extremities. Paresis can be caused by nervous system disorders, stimulus transmission disorders or the muscles themselves.Often, the basic muscle tone remains largely intact. Paralysis results from destruction of the affected nerves or even severance of the pyramidal nerve tracts in the spinal cord. Basic muscle tone is not preserved in paralysis. In addition to paralysis, muscular hypotonia can also cause decreased muscle tone. This phenomenon causes the basic tone to decrease, but does not eliminate it. For example, if one leg is affected, the physician can still place the patient’s leg in any position despite the paralysis symptoms. Hypotension can occur as a result of stroke– or trauma-related cerebellar hemorrhage. Hypotonia is also conceivable in the inflammatory autoimmune disease multiple sclerosis, which can affect both the motor pathways of the spinal cord and the cerebellum. Phenomena of pathologically increased muscle tone are to be distinguished from complaints due to decreased muscle tone. Such phenomena may manifest themselves, for example, in spasticity or rigidity. In rigidity, the muscle tension is so high that the limb stiffens. If the arm is affected, for example, it can hardly be bent. There is increased muscle resistance to external influences. Spasticity, on the other hand, refers to increased tension that forces the extremities into unnatural postures. Spasticity usually results from flaccid paralysis. These flaccid paralyses, in turn, are usually related to damage to the central nervous system.
