sleep.part 2 deatails and methods to understand

a nice reference article

1. SLEEP Sleep is defined as unconsciousness from which the person can be aroused by sensory or other stimuli. Sleep is the natural periodic state of rest for mind and body with closed eyes characterized by partial or complete loss of consciousness TYPES OF SLEEP Sleep is of two types: 1.Rapid eye movement sleep or REM sleep or paradoxical sleep 2.Non-rapid eye movement sleep, NREM sleep or non-REM sleep