john.serafin wrote "Eye movements are not controlled by autonomic systems. The poster may have been thinking about functions like pupil dilation/contraction, which are, in fact, controlled by parasympathetic system. But movements of the eye are under separate control."
John is absolutely correct. And this is the precise reason that sleepwalking onlky occurs in non-REM but sleeptalking occurs in both REM & non-REM. During REM there are inhibitory messages sent from the hindbrain to the spinal motor neurons. But speech is controlled by crainial, not spinal nerves. Then he wrote ".......... describing the effect as motor paralysis is probably an overstatement. Brainstem areas, during REM, inhibit motor neurons in the spinal cord. That does not necessarily imply total paralysis." That is also true. During REM, the major postural muscles exhibit a flaccid paralysis but during REM there are frequent small muscle movements. Then he asked, "Some species sleep standing up. Why don't they flop over and fall down when they enter REM?" Clearly, natural selection favors neurological mechanisms that are adaptive during REM. As Carol pointed out for bovines, this usually means causing the knees to be locked but it probably also means inhibiting descending excitatory messages from the brain to the large postural muscles but without the dramatic loss of muscle tone seen in e.g., primates, felids, canids, etc.). Another great example would be the sloth that sleeps while hanging upside down from a branch. Edward I. Pollak, Ph.D. Department of Psychology West Chester University of Pennsylvania ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Husband, father, grandfather, biopsychologist, & bluegrass fiddler...... in approximate order of importance. --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=830 or send a blank email to leave-830-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
