Stage+N2

The second of the stages of sleep is N2. Adults spend around half all time sleeping at stage N2. The characteristics of N2 sleep spindles (0.5-1 second EEG periods of 12-16 Hz waves) and K-complexes (short periods of brain activity that last about the same length of time and follow sleep spindles) K-complexes most of the time appear randomly throughout N2 sleep, but also happen in response to auditory stimuli, like if someone knocks on the door of a sleeping  person. During N2, conscious awareness of the outside world disappears and the muscles relax.

A sleep spindle is a period of faster brain activity. They are the result of the cells in your thalamus talking to the cells in your cortex. It contains of 13-17 Hz brain waves that happen for 0.5 to 1.5 seconds. Sleep spindles can represent certain times when the brain is trying to keep the rest of the body relaxed. Sleep spindles often signal the beginning of Stage N2 sleep, and they often decrease toward the beginning of N3 sleep. Sleep spindles usually can be picked up by EEGs easiest in the frontal and central lobes. All sleep spindles come immediately after muscle twitches. Scientists believe that, especially in younger kids, the brain is learning what nerves control what muscles.

A k-complex is a different form of faster brain activity. It comes before the sleep spindle and is shorter and bigger. It is considered the largest brain event in healthy human EEG. A K-complex has 2 purposes, it suppresses cortical arousal and helps sleep based memory consolidation (storing memory). K-complexes usually happen every 1 to 1.7 minutes, they happen when responding to changes in the environment, internal changes, and at random times.

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 * Table of Contents: **
 * = REM ||= Stage N1 ||= Stage N2 ||= Stage N3 ||
 * = Sleeping Habits ||= Sleeping Disorders ||= Bibliography ||=  ||