The sleep is a reversible physiological state. We sleep about one-third of our lives. Sleep has the function of restoring the body. We need about 8 hours of daily sleep in order to recharge our body’s batteries. Less sleep or more is associated with obesity, diabetes, or other illnesses. Scientists have looked for answers to questions such as what are the functions of sleep and why do we sleep? More or less, they found the answers to these questions but many other questions arise. Why do we dream? Are dreams and brain disease connected? Are REM sleep cells linked to disorder? Let’s see what we got so far.
Types of sleep
Sleep is of two types, each with its features:
- REM (rapid eye movement)
- Non-REM (non-rapid eye movement), with four stages of depths of 1,2,3 and 4
Sleep of the non-REM type
Each sleep cycle begins with stage 1 of non-REM sleep. There are exceptions to people with sleep disorders.
This sleeping state lasts on average for a few minutes, accounts for no more than 5% of the total sleep, and the awakening is easily done to auditory and tactile stimuli.
Non-REM stage 2 takes approximately 10-20 minutes. Stage 2 represents approximately 50% of total sleep time. Awakening is harder to accomplish during this phase.
Stages 3 and 4 are encountered at the beginning of the sleep phase. Stage 3 lasts for a short period of minutes and represents an average of about 5% of total sleeping time. Stage 4 lasts on average 20-40 minutes in the first sleep cycle and represents up to 15% of total sleep.
Sleep of the REM type
It is a deep sleep, muscle tone disappears, reflexes diminish, and rapid eye movements are recorded. The duration of REM sleep is of a few minutes in the first cycle. During this REM sleep the periods of dreams come in.
Changes during sleep
During sleep, physiological changes occur:
- Decreases blood pressure
- Decreases pulse rate
- Reduces brain activity
- Decreases breathing frequency
- Slows metabolism
- Reduced renal function, less urine
- Stimulates endocrine function, certain hormones as growth hormones, thyroid hormones as well as melatonin are secreted during sleep
What is melatonin?
Melatonin is a hormone secreted by the pineal gland in order to regulate the circadian rhythm. Melatonin is secreted at night and induces sleep.
What is the circadian rhythm?
Circadian rhythm is the biological activity and behavior over a 24-hour period related to the light-dark cycle.
It seems that human beings have a biological horology that dictates biological rhythms and activities over a day.
The headquarters of this horology are in an area of the brain called the hypothalamus.
Sleep patterns throughout life
During life, the characteristics of sleep, also known as sleep patterns, duration, and sleep efficiency are changing.
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