Effect of rectal mechanoreceptor stimulation on the striated musculature

Summary

It was shown in acute experiments on cats (urethan anesthesia) that the threshold value and the character of the striated muscle reaction in response to interoceptive stimulation depends on the intensity of the receptor stimulation and the system of functional connection between the given muscle and the area stimulated.

With a rise of the stimulation intensity of rectal mechanoceptors there primarily occurs a reaction of the anal sphincter, at first (in 50% of experiments) in the form of relaxation, with a somewhat greater stimulation intensity —in the form of contraction, followed by a relaxation, this time more complete. Abdominal muscles begin to react with a somewhat greater stimulation intensity (by relaxation with low stimulation values, and by contraction with higher ones).

Muscles of the lower extremities also react in the same way; however, their relaxation occurs already with medium, and contraction — with higher stimulation values. Finally, with the greatest stimulation intensity reflex threshold is reached in the cervical muscles — they relax in response to all the effective stimulation intensities.