Tone is an active state of the nerve centers and associated peripheral units, ensuring that any function at optimum levels.
Depending on the location toniceski excited peripheral muscle formations distinguish the tone of skeletal muscles, tone of blood vessels, the tone of the stomach, intestines, etc.,
Usually changes the tone of the nerve centers cause changes in relevant peripheral organs which is one of the ways of regulation of the vital functions of the organism. So, for example, decrease heart rate can be achieved either by strengthening tone nucleus of the vagus nerve, or the weakening of sympathetic tone centers.
The tone of the nervous centres and associated peripheral units depends on three main factors: from the entrance to the nerve centres of afferent excitations that amplify or, on the contrary, weaken the degree of the tonic of excitation of these centers, from the effects on nerve centers of different humoral stimulation and interaction between the centres.
For example, the tone of skeletal muscles depends primarily on the receipt to the motor neurons of the spinal cord continuous afferent excitations from proprioception of the muscles themselves. Deafferentiation muscles leading to a sharp decline in its tone.
In the regulation of muscle tone important role played by a number of departments of a brain. These include the reticular formation of the brain stem, vestibular nuclei of medulla oblongata, the structure of secondary brain (red kernel, black substance), the cerebellum, striopallidarna system and, finally, the motor areas of the cerebral cortex.
Only through the combined activities of all the above entities can be very complex process of regulation and redistribution of muscle tone. With the defeat any of the above mentioned structures can be observed numerous varieties of pathology of muscle tone. So, for example, with the defeat of the red medium nuclei of the brain develop phenomenon of hypertonic, muscle rigidity-extensors. With the defeat in striopallidarna system develops hypotension of various muscle groups, with the defeat of the motor areas of the cerebral cortex - the rising tone (spasticity), etc.
The Central entities, providing regulation of muscle tone, play an important role and humoral factors, such as adrenaline, carbon dioxide , etc.,
However, in more emphatic manner monogenea the value of these humoral stimuli is manifested in the activities of the vasomotor center, ensuring a certain tone of peripheral vessels (see Blood pressure).