Night Terrors occur when you are in deep sleep, and there is little if any recall associated with them. Sleep Paralysis occurs if you awaken following REM (dream) sleep, which is very different from deep sleep.
When you first drift off to sleep you enter "Stage 1", your brain waves change to a slower pattern than the normal brain waves of an awake person. Muscles relax, and you might waken suddenly by a sensation of falling. Next, you enter "Stage 2" and the waves get slower, with sudden short bursts of higher frequency brain waves. The next stage is "Stage 3" with even slower brain waves - this is a pretty deep sleep. If you're young enough, you will next enter "Stage 4" - the deepest sleep, with the slowest brain waves. It is difficult to rouse someone from Stage 4 sleep. THEN - you return to Stage 3, then Stage 2, and then you enter REM sleep (note, you don't return to Stage 1) during which the brain waves resemble normal awake brain waves. This is why it is often referred to as paradoxical sleep. After a (hopefully) nice dream, you progress down through stages 2 to 4 again, and back up to REM. You repeat this several times during the night.
As always, Dr. Chudler at UW has a wonderful page on this (so what if it's for kids - it's still a great page) - http://faculty.washington.edu/chudler/sleep.html
This page has a nice list of how sleep paralysis and night terrors differ in symptomotology http://www.trionica.com/asp/conditions/nightterrors.htm
REM behavior disorder is a pretty cool topic, too (although I wouldn't want to have it) - this is where the paralysis that should occur during REM is not in effect, and people act out their dreams.
When you first drift off to sleep you enter "Stage 1", your brain waves change to a slower pattern than the normal brain waves of an awake person. Muscles relax, and you might waken suddenly by a sensation of falling. Next, you enter "Stage 2" and the waves get slower, with sudden short bursts of higher frequency brain waves. The next stage is "Stage 3" with even slower brain waves - this is a pretty deep sleep. If you're young enough, you will next enter "Stage 4" - the deepest sleep, with the slowest brain waves. It is difficult to rouse someone from Stage 4 sleep. THEN - you return to Stage 3, then Stage 2, and then you enter REM sleep (note, you don't return to Stage 1) during which the brain waves resemble normal awake brain waves. This is why it is often referred to as paradoxical sleep. After a (hopefully) nice dream, you progress down through stages 2 to 4 again, and back up to REM. You repeat this several times during the night.
As always, Dr. Chudler at UW has a wonderful page on this (so what if it's for kids - it's still a great page) - http://faculty.washington.edu/chudler/sleep.html
This page has a nice list of how sleep paralysis and night terrors differ in symptomotology http://www.trionica.com/asp/conditions/nightterrors.htm
REM behavior disorder is a pretty cool topic, too (although I wouldn't want to have it) - this is where the paralysis that should occur during REM is not in effect, and people act out their dreams.
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