Sleep: Understanding the Basics

• Basics of Sleep Introduction
• Importance of Sleep
• Stages of Sleep
• Sleep at Different Stages of Life
• Circadian Rhythms That Influence Sleep
• Substances That Alter Sleep
• Sleep Deprivation
• For More Information
• Web Links
• Synonyms and Keywords
• Authors and Editors
• Related anemia article:
  Sleep Apnea - on WebMD

Basics of Sleep Introduction

Sleep is defined as a state of unconsciousness from which a person can be aroused. In this state, the brain is relatively more responsive to internal stimuli than external stimuli. Sleep should be distinguished from coma. Coma is an unconscious state from which a person cannot be aroused. Sleep is essential for the normal, healthy functioning of the human body. It is a complicated physiological phenomenon that scientists do not fully understand.

Historically, sleep was thought to be a passive state. However, sleep is now known to be a dynamic process, and our brains are active during sleep. Sleep affects our physical and mental health, and is essential for the normal functioning of all the systems of our body, including the immune system. The effect of sleep on the immune system affects one’s ability to fight disease and endure sickness.

States of brain activity during sleep and wakefulness result from different activating and inhibiting forces that are generated within the brain. Neurotransmitters (chemicals involved in nerve signaling) control whether one is asleep or awake by acting on nerve cells (neurons) in different parts of the brain. Neurons located in the brainstem actively cause sleep by inhibiting other parts of the brain that keep a person awake.  

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