It’s a spiral.  You repeatedly climb up and down it.  As you do, images of the “Remains of the Day”, the residue of the past and all your concerns for the future are represented in dreamscapes; hung in an array of gilded frames along the pathway of your journey.

We spend approximately 1/3 of our lives in sleep. 

An estimated 40% of the population suffers from sleep deficit; some touting they can perform efficiently on a mere 4-6 hours. A 2005 poll conducted by the National Sleep Foundation showed we average 6-8.5 hours of sleep weeknights; 1 hour less than needed.  Since the invention of the light bulb, our activity has increased well-passed early evening hours into the night; our original sleep cycles have evolved in such a way that many medical conditions can be linked to sleep deprivation.  In order for sleep to be recuperative so as we don’t suffer from deprivation, each stage of the sleep cycle must be completed.  While our bodies are more than willing to make up for lost sleep, it takes an aggressive discipline and strong level of commitment of keeping to a schedule for several weeks or more in order to return to normal sleep architecture (or pattern).

The architecture of sleep is the alternating of REM and NREM.  There are 4 stages and REM, which comprise sleep architecture.  We revisit this architecture every 90-110 minutes during sleep each night.

 

Stage 1 – 5% of NREM is spent in this stage.  it’s a transitional period in which you begin to doze or fall asleep, sometimes experiencing sudden jerks and/or the sensation of falling; the stage you can be easily be awakened from.

Stage 2 – 45% of NREM is spent in this stage.  This stage is the beginning of consolidated sleep (unbroken sleep) development. 

Stage 3 –12% of NREM is spent in this stage. Here an individual is much harder to awaken.

Stage 4 – 13%of NREM is spent in this stage. The final stage of the sleep cycle, which amounts to 75% of NREM.  In this stage an individual has reached the deepest sleep.  An individual in either 3 or 4 is more difficult to awaken and will feel groggy and require a few minutes to reach full consciousness.

REM sleep – the stage of dreams.  Sometimes referred to as “paradoxical sleep” because brain activity is very much the same as if we were awake.  During this stage, your eyes flutter, the brain blocks signals to your muscles creating a paralysis so dreams can’t be acted out.  Here REM is distinguished from NREM by irregular breathing, the lowering of body temperature, heart rate, and blood pressure.           

All in all, NREM is the cycling of these stages plus REM.

 

It’s not known ‘why we go to sleep’, but there is enough data to explain what happens in sleep, and what happens if we don’t. So far, science has uncovered a correlation between sleep deficit and medical conditions such as obesity, diabetes, and immune system dysfunction.  The causes of sleep deficit can be attributed to poor sleeping habits or clinically diagnosed ‘insomnia’. 

Statistically, ‘insomnia’ is first in line in investigating sleep deprivation. Insomnia can last either for either a few days (transient) or for months (chronic). Those afflicted, experience symptoms of, ‘sleep initiation insomnia’ (falling asleep) or ‘sleep maintenance insomnia’ (early awakening or remaining asleep).  Other indications include:1 or 2 long episodes of being wide awake after going to bed, constant short awakenings and early morning awakenings. When ‘insomnia’ is the major cause of sleep deprivation, scientists take into consideration how effectively our ‘biological’ clock or ‘circadian rhythm’ manages a days’ 24-hour cycle.

The term ‘circadian rhythm’ (‘circa’ meaning about and ‘dies’ meaning day) applies to physiological functions i.e., breathing, body temperature, hormones and of course, our sleep/wake cycle which operates each 24-hour period.  All living creatures have this circadian biology –even single-cell organisms like bacteria. Two small areas in the back of the hypothalamus in the brain called the ‘suprachiasmatic nuclei’ or scn perform the orchestration of our circadian rhythm.

            The location of the scnis situated close to where the optic nerves cross; the cerebral cortex, thalamus and hypothalamus form the reticular activating system. The pineal gland is a pine shaped gland, hence its name works in conjunction with the hypothalamus, directing the body's thirst, hunger, and sexual desire; a biological clock within itself, that determines our aging process.   The production of melatonin (a derivative of the amino acid tryptophan which induces sleep) by the pineal gland is stimulated by the retina’s signaling of light.  

It is a neuro-chemical called adenosine that keeps us awake during the day.  This action is because adenosine cannotbind to its matching receptor therefore the feeling of drowsiness is delayed. Each morning we awaken, we begin the process of building sleep architecture.  This wakefulness is because of the binding of adenosine with phosphorous converting it to adenosine triphosphate or ATP, a substance cells break down in order to generate energy.  In a briefing on the “brain”, the society for neuroscience, explains how sleep is introduced,

“With each invigorating burst, atp loses a molecular appendage called a phosphate. Finally, atp is dwindled down to adenosine.”

By evening, the pressure of adenosine builds in the basal forebrain, which relays to the scn to signal the secretion of melatonin.

Before 1978 it was argued whether man had evolved beyond ‘light’ being responsible for our sleep/wake cycle or whether social interaction played a more important role. 

            The scn’s response to light causes the secretion of the hormone melatonin to cease, otherwise we would eventually evolve as a civilization that did nothing else but sleep – or never sleep. 

Until recent, studies, melatonin was thought to have more of significance than the reaction of light. In circadian biology, adenosine, ATP and the scn act in concert creating our sleep/wake cycle and ‘light’ as the presiding factor.

            In this 2-part journey of exploring sleep debt & circadian biology; next stop: insomnia and sleeping aids.