Sleep is a major aspect of a person's health and is immensely necessary for the human body to function in a proper manner. Overall there are four stages of sleep. The first stage is defined as the transition stage that occurs between the wakefulness phase and the sleep phase. In addition to that, the first stage is marked by cognitive patterns in the form of relatively swift waves of low-voltage. This stage is followed by the second stage which is of a deeper nature as compared to the erstwhile stage. The second stage contains a slower and more regular frequency of patterns, which is marked with a series of momentary interruptions called 'sleep spindles'.
Then comes the third stage of sleep, which comprises of waves that are even slower than they were in the second stage, nevertheless the pattern is not so even with a number of peaks and valleys occurring in between the wave pattern. The last and fourth stage of sleep is by far the deepest stage of sleep in which the person is almost unconscious while the degree of responsiveness in a person is the least as compared to the previous three stages.
Then comes the third stage of sleep, which comprises of waves that are even slower than they were in the second stage, nevertheless the pattern is not so even with a number of peaks and valleys occurring in between the wave pattern. The last and fourth stage of sleep is by far the deepest stage of sleep in which the person is almost unconscious while the degree of responsiveness in a person is the least as compared to the previous three stages.