I'm kind of enjoying this thread and thank all of you for your thoughtful contributions. But, what about birds? I understand that birds' toes naturally curl in their 'relaxed' position, which is why you see them curled up when one finds them dead. So, I guess that the natural grip of the branch is what one of the reasons why they don't fall when they are in REM. If that is so, how do they keep themselves balanced?
Miguel ----- Original Message ----- From: "Edward Pollak" <[email protected]> To: "Teaching in the Psychological Sciences (TIPS)" <[email protected]> Sent: Wednesday, February 24, 2010 9:24:31 AM GMT -05:00 US/Canada Eastern Subject: Re:[tips] Great Question about REM 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 al so 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. 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=13482.917fac06d4daae681dabfe964ca8c74e&n=T&l=tips&o=830 (It may be necessary to cut and paste the above URL if the line is broken) or send a blank email to leave-830-13482.917fac06d4daae681dabfe964ca8c...@fsulist.frostburg.edu --- 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=831 or send a blank email to leave-831-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
