Final answer:
NREM Stage 3 and REM sleep are the stages of sleep often referred to as deep sleep or slow-wave sleep. NREM Stage 3 is characterized by low frequency, high amplitude delta waves, while REM sleep is marked by high brain activity and lack of muscle tone.
Step-by-step explanation:
Stages of sleep that are often referred to as deep sleep or slow-wave sleep are NREM Stage 3 (non-REM stage 3) and REM sleep.
NREM Stage 3, also known as deep sleep or slow-wave sleep, is characterized by low frequency (less than 3 Hz) and high amplitude delta waves. During this stage, the heart rate and respiration slow dramatically, and it is difficult to awaken someone from sleep.
REM sleep, which stands for rapid eye movement sleep, is the stage of sleep in which dreaming occurs. This stage is characterized by high brain activity and lack of muscle tone.