The receptive organs of the muscular sense and of the semicircular canals are to be regarded as the sites of origin of this reflex tonus of the skeletal muscles.
Striped muscles possessing an autochthonous tonus appear to be the various sphincter muscles.
There slowly successive phases of increased and of diminished tonus regularly alternate, and upon them are superposed the rhythmic "beats" of the pulsating heart.
In tracing the tonus of neurons to a source, one is always led link by link against the current of nerve force - so to say, "up stream" - to the first beginnings of the chain of neurons in the sensifacient surfaces of the body.
From these, as in the eye, ear, and other sense organs, tonus is constantly initiated.
Thus the tonus of the motor neurons of the spinal cord is much lessened by rupture of the great afferent root cells which normally play upon them.
A prominent and practically important illustration of neural tonus is given by the skeletal muscles.
It is a muscular tonus of central source consequent on the continual glow of excitement in the spinal motor neuron, whose outgoing end plays upon the muscle cells, whose ingoing Yet when the muscular contraction is taken as index ology.
It is with the neural element of muscle tonus that tendon phenomena are intimately associated.
The muscles become less tense than in their waking state: their tonus is diminished, the upper eyelid falls, and the knee-jerk is in abeyance.