Sleep
Level 1 sleep is a transition period between sleep and wakefulness; Level 2 sleep features significant slowing of heartbeat and breathing, and makes up about 50 percent of all sleep; and Level 3 and 4 (Delta) sleep are marked by very slow respiration and heartbeat. Level 4 sleep leads to rapid eye movement (REM) sleep, also known as Level 5 sleep.
Dreams occur during three to five periods of REM sleep each night. REM sleep occurs at intervals of one to two hours, and is variable in length. REM sleep is characterized by irregular breathing and heart rate, and involuntary muscle jerks.
Most adults need around eight hours of sleep on a regular schedule to function well, although some require less, and others more. (It has been said that men need an hour less sleep than women.) Children, particularly teenagers, often need nine or ten hours for optimal functioning.
Read Also:
- Sleep apnea, central
A breathing disorder characterized by brief interruptions of breathing during sleep. Central sleep apnea occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations. Central sleep apnea is less common than obstructive sleep apnea. Diagnosis is by observation, patient history, and polysomnography. Treatment depends on the patient’s medical […]
- Sleep apnea, obstructive
central and obstructive. Central sleep apnea occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations. Obstructive sleep apnea occurs when air cannot flow into or out of the person’s nose or mouth although efforts to breathe continue. Obstructive sleep apnea is much more common than central sleep […]
- Sleep disorders
Any disorder that affects, disrupts, or involves sleep. The most common sleep disorder is probably snoring, although it is usually not medically significant. Insomnia, sleep apnea, restless leg syndrome, and sleepwalking are also sleep disorders. Most large medical centers have diagnostic and treatment facilities dedicated to sleep disorders. See also sleep apnea, sleepwalking, snoring.
- Sleep drug
Any drug used to help sleep. Most prescription sleep drugs are sedative hypnotic agents. They include Valium, Xanax, Restoril, Ambien, and Sonata.
- Sleep hygiene
McGraw-Hill Professional, 2008.