Final answer:
During stage 2 NREM sleep, brief bursts of slow waves are characterized by sleep spindles and K-complexes, with sleep spindles having potential roles in learning and memory and K-complexes possibly reacting to environmental stimuli.
Step-by-step explanation:
Brief bursts of slow waves during stage 2 NREM sleep are characterized by sleep spindles and K-complexes. Sleep spindles are a rapid burst of higher frequency brain waves that may be important for learning and memory. K-complexes are a very high amplitude pattern of brain activity that may in some cases occur in response to environmental stimuli, which may serve to bring us to a higher level of arousal in response to what is going on in our environments. Stage 2 sleep is also where the body goes into a state of deep relaxation and theta waves still dominate.
REM sleep, on the other hand, is marked by rapid eye movements and brain waves that resemble those seen during wakefulness. REM sleep is often referred to as paradoxical sleep due to its combination of high brain activity and lack of muscle tone, excluding muscles that facilitate circulation and respiration.