Sleep

Why do we do it? When there’s a lot to do, it seems like such a waste of

time……

Theories

• Restorative Theory – sleep to replenish essential bodily processes (go to bed tired, wake up refreshed– Pros : when we exercise, we have more slow-

wave sleep; lack of REM sleep can cause mood and thought problems

– Cons: “second wind”, physiological data do not support this theory

• Adaptive Non-responding Theory – sleep and inactivity have developed evolutionarily. As an example, successive generations sleep less

Circadian Rhythms

• Free running rhythms. Our internal clocks are set on a 25 hour day, yet we force our bodies into a 24 hour pattern. The body adjusts to a “down time,” which is generally between midnight and 6 am. This is the time span when most accidents (Three Mile Island, Chernobyl, etc.) happen as people are forced to ignore their Circadian Rhythms.

Sleep Cycle

• Awake – low voltage, high frequency beta waves

• Drowsy – alpha waves

• Stage 1 Sleep – brief transition between being awake and asleep, Theta waves

• Stage 2 Sleep – deeper sleep, sleep spindles, mixed EEG activity

• Stages 3 and 4 Sleep – deepest sleep, muscle tension, heart rate, and breathing decline – progressively more Delta waves. Also known as Slow Wave Sleep.

• Stages 1 – 4 are non-REM (NREM) sleep

REM Sleep

• Rapid Eye Movement – This is where most vivid dreams happen. Low voltage, high frequency waves (much like when awake)

• There are dreams that occur outside of REM. Somnambulism and sleep talking also occur outside of REM, usually in stages 1 and 2, midway through the night cycle.

• The whole sleep cycle is repeated about 4x per night. The REM period gets longer each time.

Neural and Chemical Bases of Sleep

• No one single brain structure is responsible for sleep.– Reticular formation (in the core of the brain

stem) Fibers from the reticular formation extend to many other brain areas. (ascending reticular activation system)

– Pons – critical to REM sleep– Medulla, thalamus, hypothalamus, limbic

system are all involved in sleep

• No one single neurotransmitter is responsible for sleep either.– Serotonin, GABA, norephinephrine, dopamine

acetylcholine and melotonin all involved.

Sleep Disorders

• Insomnia – can be a problem getting to sleep, a problem staying asleep or a problem of waking too early in the morning

Insomnia is causes daytime fatigue, impaired functioning, accidents, absenteeism, reduced productivity, depression and health problems.

• About 35% of adults report some insomnia. It increases with age and is about 50% more common in women than men.

• Caused by stress, anxiety, muscle tension, depression. It can also be caused by physical pain, asthma, etc.

• Insomnia is often treated with medications, however, they can lead to a cycle of tolerance, increased dosage, greater tolerance, etc.

Narcolepsy

• Narcolepsy is the sudden onset of REM sleep during normal waking periods. Usually 10 – 20 minutes of duration.

• Can be extremely serious.

• Usually treated with stimulants.

Sleep apnea

Sleep apnea is the reflexive gasping for air person awakening. Subject stops breathing for 10 or more seconds.

Treated with surgery, medications or a variety of mechanical apparatus.

Nightmares

• Anxiety causing dreams awakening from REM sleep

• More common in children than in adults

Night terrors

• Abrupt awakening from NREM sleep accompanied by feelings of panic and rapid heart rate.

Somnambulism

• Occurs during NREM

• Seems to be some genetic predisposition

• More common in children than in adults