What are the 4 stages of quiet sleep?

Quiet sleep (stages N1, N2, N3, and N4) begins with the transition from wake to state 1. During this state, the eyes will begin to close, and the person may experience a brief sensation of falling or jerking. The EEG wave pattern associated with stage N1 is somewhat slower than that of the awake state.

Stage N2 sleep consists of sleep spindles, bursts of rapid, high-amplitude, rhythmic activity lasting for 1 to 2 seconds and occurring every 15 to 30 seconds. Alpha waves are also seen in stage N2. Stage N2 sleep typically constitutes 50% of total sleep time.

Stage N3 is characterized by delta waves, high amplitude slow waves that occur at a frequency of 0.5 to 2.0 Hz. Stage N3 sleep typically constitutes about 20 to 25% of total sleep time.

Lastly, stage N4 is characterized by both slow delta waves and rapid K-complexes. K-complexes are large, sharp, biphasic waves lasting for 1/2 to 1 second. Stage N4 sleep typically constitutes 15 to 20% of total sleep time.