What is sleep?
A periodic, natural, loss/change in consciousness, distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation.
What are the characteristics of sleep? Describe each one (4).
- Immobility
- Posture
- Responsivity
- Reversibility
What waves are present when you are falling asleep?
Alpha and beta waves.
What waves are present in stage 1 sleep?
Slower, theta waves emerge.
What waves are present in stage 3 sleep?
Theta waves gradually become slower and slower, until delta waves emerge.
What waves are present in stage 4 sleep?
Mostly delta wave sleep. This is also known as slow-wave sleep (SWS) or non-REM sleep.
What waves are present in stage 2 sleep?
Very similar to stage 1 (theta waves), every once in a while there is a jittery spike in activity called a “sleep spindle”. We are on our way into deep sleep.
What waves are present during REM sleep?
The waves increase in frequency to beta waves, although we are in deep sleep (paradoxical sleep). The eyes are swishing back and forth, but muscles are paralyzes so we do not act out our dreams.
At which stage of life is REM sleep more prominent?
During infancy and childhood. REM is important for development, but SWS is the most important for restoration.
The proportion of the night spent in REM rapidly decreases as we get older.
- 70% in a newborn
- 30% in a 6 month old
- 15% in an adult
Do other species sleep?
Yes, all other animals sleep. If sleep did not have a vital function, it would have been evolved out a long time ago. There are consequences if we do not get enough sleep.
What is total sleep deprivation?
The equivalent to pulling an all-nighter - where one has not gotten ANY sleep.
What is a delta rebound?
The night after TSD, you don’t sleep for double the amount of time, you just spend more time in stage 3/4 deep sleep.
*there is also a bit of REM rebound, but it is not as prominent.
What is sleep restriction?
When you get some sleep, but not enough.
Briefly, what happens when we do not get enough sleep?
Decreased alertness, attention and sociability - related to parietal lobe activity. Also impaired executive functions, driven by the PFC.
Increased fatigue, irritability, and RTs.
Other health risks, such as a suppressed immune system, risk of CVD and stroke, risk of depression, correlations with some cancers, and accumulation of wastes in the brain.
What is hyperphagia?
Impaired memory formation and recall of verbal material.
What is a “sleep debt”?
An accumulated debt when one gets less than 5hrs of sleep a night for an extended period of time.
*everyone, and different mammals, need different amounts of sleep.
Which brain areas and NTs are responsible for REM sleep?
The pons contains AcH neurons that help transition from SWS to REM. We do not have REM if the pons is damaged.
Other involved areas:
- The cortex (dreaming)
- Midbrain also contributes to REM
- Inhibitory neurons inhibit the PMC during REM
Which brain areas and NTs are responsible for SWS?
The entire brainstem, which contain serotonin neurons.
The basal forebrain, which contains GABA. This is the main driver of SWS.
The preoptic area of the hypothalamus - also contains GABA. This is the easiest area to stimulate when researching sleep, and changes in sleep are very obvious when it is damaged or stimulated.
What is our “circadian rhythm”?
Our internal 24hr clock, our biological cycle of day and night. This governs our feelings of hunger throughout the day, blood sugar levels, and hormone release.
What area of the brain controls and syncs all of our cells’ rhythms?
The suprachiasmatic nucleus in the hypothalamus. If this is damaged, animals will act in an unsynchronized, scattered manner.
What is a zeitgeber? What is the most important one?
A physical stimulus that regulates our clocks, and gives us an indication of what time of day it is and how we should behave.
The most important one is sunlight.
How is sunlight, as a zeitgeber, detected?
Specialized proteins on the retina reserve this sunlight to be projected to the SCN, not the visual cortex.
What is melatonin?
A chemical released by the pineal gland. It is released when there is no light stimulus, and is not released when there is a light stimulus.
It does not actually help us fall asleep.
What is “social jet lag”?
Happens when the circadian clock is delayed (like a mini jet lag). To prevent this, we should wake up at the same time every day.
