What is the definition or description of: sleep paralysis?

Narcolepsy: Part of the narcolepsy syndrome which includes daytime irresistible sleep attacks, hypnagogic hallucinations, cataplexy. When the pt awakens in the morning, may experience a few seconds of inability to move, but this is transient, not permanent and treatment of the sleep disorder can quell this symptom.

Sleep paralysis:: Occurs in rem-sleep when the output from the rem-on neurons, located within the pons, travels along a two-cell relay beginning in the locus ceruleus and ending at the motor neurons of the spinal cord. The end result is deep suppression of output to the voluntary muscles, approaching full paralysis. The activity of the muscles of the diaphragm, of the hyoid and of eye movement are spared.

Sleep Paralysis: Sleep researchers conclude that, in most cases, sleep paralysis is simply a sign that your body is not moving smoothly through the stages of sleep. Rarely is sleep paralysis linked to deep underlying psychiatric problems. http://www.webmd.com/sleep-disorders/guide/sleep-paralysis#1