Sleep: A crucial process for resetting brain and body health.
Complex Physiological Process: More intricate than just losing consciousness for several hours.
Stages of Sleep
Deep Sleep: Changes in brainwave activity are significant compared to wakefulness.
REM Sleep (Rapid Eye Movement): Known as dream sleep; some brain areas can be 30% more active than when awake.
Paradox of Sleep
Common misconception: Sleep is a passive state.
Reality: Sleep is an active state with various physiological changes.
Questioning the evolution of sleep: What if sleep was the original state, and wakefulness evolved from it?
Types of Sleep Across Species
Sleep in humans and mammals is divided into two main types:
Non-Rapid Eye Movement (NREM) Sleep
Rapid Eye Movement (REM) Sleep
REM Sleep
Characteristics:
Also referred to as paradoxical sleep due to high brain activity and body paralysis.
Difficulty distinguishing between awake and REM states based on brain activity alone.
Eye Movements: Horizontal shuttling eye movements during REM; distinguishes between REM and waking states.
Paralysis Mechanism: Brainstem signals cause temporary paralysis of voluntary muscles to prevent acting out dreams.
Autonomic Activity: During REM, autonomic storms occur affecting heart rate and blood pressure, leading to physiological responses (e.g., erections and vaginal lubrication).
Stages of NREM Sleep
NREM is further divided into four stages (1-4), increasing in depth:
Stages 1 and 2: Light sleep.
Stages 3 and 4: Deep sleep.
Sleep Cycle
Typical Sleep Duration: 7-9 hours (varying by individual).
Sleep Architecture:
Initial hours consist primarily of deep NREM sleep.
Later hours transition to lighter NREM and more REM sleep.
Cycle Duration: Each cycle lasts about 90 minutes, repeating several times during the night.
Personal Sleep Example**
Sleeping pattern example:
Sleep from around 10:30 PM to 7:00 AM.
First hour: Transition from light NREM to deep NREM.
After about 60-70 minutes: First REM period occurs.
Ratio Change: The ratio of NREM to REM changes throughout the night:
More deep NREM in the first half, more light NREM and REM in the second half.
Conclusion
Understanding the complex nature of sleep can help improve daily life and health.