Monday, August 28, 2006

All about sleep and dreams

There are basically 5 stages of sleep in a sleep cycle, categorised by the types of brain waves. Each of this cycles lasts about 90-100 minutes and recurs several times during the night.

The 1st (lasting till 10 min) and 2nd (20min) are relatively light stages, so if people are awaken during one of these stages, they often report not having been asleep at all.

The 3rd and 4th have the slowest and highest amplitude of brain waves during sleep. Brain waves during these stages are least like waking brain waves. So if people are awakened during these stages, they usually are confused and disoriented.
After 1st-4th stage, sleepers drift towards wakefulness. But instead of re-entering stage 1, they enter rapid-eye-movement(REM) sleep. During REM sleep, the sleeper's eyeballs move up and down and from left to right. REM sleep is an active stage where dreaming usually occurs. Dreams at this stage are typically longer, more vivid, more emotionally charged, and less related to waking life.

Our body follows a circadian rhythm. This rhythm involves the sleep/wake cycle, body temperature, blood pressure, and blood sugar level. For example, body temperature fluctuates about 3' Fahrenheit, peaking in the afternoon and reaching in its lowest point betweeen 2am to 5am.
Researhers had conducted experiments to see what happens to the biological clock when individuals are completely isolated from clocks, calendars, night, the moon, the sun, and all indices of time. Volunteers were placed in isolation so they lived by biological cycles instead of by days. Each of their sleep/wake cycles are considered as a day. Results showed that their day only vary from 24 hours by a few minutes.

When you fly to a country situated in a distinctly different time zone, you may have trouble sleeping because your body is still in the previous time zone. You usually sleep when your body temperature begins to drop, but in your new location, you may be trying to sleep when it is rising. In the morning, your body relase large doses of the hormone cortisol to help you wake up. But in your new geographical time zone, the glands may be releasing the hormone just as you are getting ready for bed at night.
How to reset your biological clock? In the new country, you should spend as much time outside in the daylight as possible. Bright light during the day, especially in the morning, increases wakefulness. When you sleep, you should sleep in complete darkness.

Sleepwalking has a more formal term - somnambulism. Contrary to superstition, it is safe to awaken sleepwalkers.

Just to share some of my psycho knowledge. Hope it's enlightening. Wahaha.

Adopted from Psychology 7th updated edition by John W. Santrock


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