Sleep: Understanding the Basics

1. Causes of Fatigue Slideshow Pictures
2. Take the Sleep Quiz!
3. Foods That Help or Harm Your Sleep Slideshow Pictures

Author:

Michael B. Russo, MD

Coauthor:

Shehnaz Shaikh, MD

Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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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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