Sleep (weeks 1 & 2) Flashcards
Sleep Basics
7 - 8 hours
we sleep 1/3 of our lives
4 stages:
-stage 1
-stage 2
-stage 3
-REM
first three are non REM
Stage 1 of Sleep - Light sleep
lightest sleep
easy to wake up
not fully conscious but also not fully aware
alpha –> theta
Stage 2 of Sleep - Longest
we drop into this if nothing wakes us during stage 1
50% of our sleep time
vital signs begin to change: heart rate slows down, body temperature drops
sleep spindles: brain activity in this stage specific to memory consolidation
Stage 3 of Sleep - Deep
deep unconscious sleep
delta brain waves
brain shrinks to 60% of normal size, creating pathways for cerebrospinal fluid to flush cellular build-up from the day’s activities, allowing the brain to detoxify itself.
most crucial stage for recovery and overall health
blood flow increases
growth hormone secretion
Most adults need 1.5 - 2 hours of deep sleep, and time spent decreases as we age
we want to avoid waking up while in deep sleep
REM (Rapid Eye Movement)
short window; dream stage
eyes physically moving in all directions
increased heart rate and brain activity
unable to voluntarily move the body
dreaming: memory consolidation, emotional processing, problem solving, and intelligence
natural awakening most likely to occur
Sleep Cycle Details
a sleep cycle refers to all 4 stages
1 cycle through is 60-90 minutes
cycles occur 4-6 times in a night
~75% is NREM
as you have more cycles, more time is spent per REM cycle, and less is spent in stage 3(deep).
Sleep Cycle Example
- A person is in stage one for about five to ten minutes
- then enters stage two for about ten to 25 minutes
- Stage three lasts 20 to 40 minutes and
- REM sleep only lasts about ten.
As each subsequent cycle begins, the amount of time spent in REM increases, with a maximum
time around 60 minutes in this stage.
Circadian rhythm defintion
a handful of hormones and bodily processes whose activity fluctuates with the rising and setting of the sun
Circadian rhythm details
no single sleep stage operates as an island
all are required for full restoration from the days activities
proper sleep cycling: normal hormonal signaling
at least 15% of repair/restore processes during the circadian rhythm
-tissues and organs
-digestion, appetite
-cardiovascular
-cognition
controlled by the suprachiasmatic nucleus (SCN) within hypothalamus
Sleep/Wake Signaling
Melatonin
-sleep hormone
-released in evenings from pineal gland
-antioxidant
-anti-inflammatory
supplementation is helpful when traveling across time zones
regulate naturally with sunlight in morning, and less light in evening
Cortisol
-stress hormone
-natural energy
-released in mornings
-performance
Enteric Nervous System
the second brain
gut health is intimately linked with nervous system
connected by the vagus nerve
-responsible for parasympathetic vs sympathetic activity
GABA - encourages sleepiness
Acetylcholine - promotes wakefulness and it’s active in REM sleep
Other stimulating factors that support alertness during the day include norepinephrine,
dopamine, and histamine. Other calming factors that support healthy sleep include oxytocin,
vasopressin, and prolactin.
Serotonin
promotes wakefulness
95% in gut. tied to gut integrity and immune system health
triggered by light
precursor to melatonin
Adenosine
byproduct of energy use
concentration builds throughout the day
triggers sleepiness
receptors blocked by caffeine
A helpful note when supporting individuals on managing caffeine is its effect on adenosine –
caffeine blocks adenosine receptors and prevents the gradual drowsy feeling we’d normally
develop from being awake and alert. Once the caffeine begins to wear off and the receptors
become available again, the common “caffeine crash” occurs as the body begins feeling all that
adenosine buildup at once, because adenosine production never stops, despite not having
access to its receptors. This cycle can alter the body in unfavorable ways: cortisol and adrenaline levels rise, which further promote wakefulness, and prevent the body from any sort
of recovery. That “caffeine crash” is also partly due to the dip in hormones: what goes up, must
come down, and as adrenaline comes down it can dip below its baseline level, further
enhancing the exhaustion effect of the crash. This can also have an unfavorable effect on blood
sugar, which can, in turn, restart the cycle of reaching for more caffeine. So, managing caffeine
intake in a bio-individual way can help mitigate the potential negative effects of adenosine
buildup.
Metabolic Hormones
Insulin
-most sensitive in the morning when metabolism is high
Leptin
-satiety hormone
-down regulated with poor sleep
Ghrelin
-hunger hormone
-up regulated with poor sleep
Metabolic Hormones - Disruption
Delaying or disrupting sleep is a stress signal and the body responds in the only way it knows how – by changing its hormonal signaling. It does this out of our best interest, but unfortunately cannot distinguish between intentional delayed sleep onset due to TV show binges as opposed to running from predators. The stress signal demands more calories, one way or another. This is why many people who have disordered sleep often find weight gain to
be a side effect.
Disrupted Sleep
insulin sensitivity also goes down with sleep deprivation
-this is also a survival mechanism in fight or flight mode, which is the message the body is receiving
during fight or flight or sympathetic nervous system activity:
-the metabolism of glucose shifts to ensure enough is circulating and available to the skeletal muscles
Circadian Rhythm Influences
timely exposure to light and dark
-on skin & in eyes
-unfiltered (no windows)
avoiding blue light and backlit screens/devices
luminance: very bright light during the day, not too bright at night
Seasonal changes
food availability and seasonality provides different forms of nutrients and energy at different times of year
more energy in the summer in the form of fruits carbs, and more hibernation in the winter in the form of hearty meals
24 hour circadian cycle
We will begin at a hypothetical wake-up time of 6 AM. Within the hour, we will see blood pressure increase rapidly. This helps wake the body up and was evolutionarily advantageous to provide quick energy at first light to avoid predation. By 6 AM, cortisol has been ramping up for a couple hours.
By 7 to 7:30 AM – or with the entrance of a full morning’s daylight into the eyes – melatonin
secretion ceases until later on in the evening. Since the body has been awake and moving for some time, and assuming one has consumed breakfast, peristalsis kicks back into gear (this is the process of wavelike motions from the smooth muscle of the digestive tract that pushes previous meals along) and a bowel movement is likely to occur within another hour, between 7:30 and 8:30 AM.
By 10 AM, the typical adult body will have the most energy and focus it will encounter all day. This is when cortisol has done its job in bringing the body to alertness – and also when most adults have finished their caffeine consumption! Many adults find they are most productive and creative around this time.
Between 2 and 5 PM the body will usually experience good coordination, reaction time, strength, and power, assuming one does not succumb to an afternoon slump. This peak physical performance is often why many experts recommend afternoon workouts instead of morning or late evening. This timing is also why an additional cup of coffee at lunchtime is not recommended – to avoid the caffeine “crash” described previously, and to rely solely on the body’s natural signaling.
After traditional dinnertime, by about 6 to 7 PM, the body can exhibit its highest blood pressure and body temperature readings. By 8 to 9 PM, cortisol secretion slows and melatonin secretion ramps back up again. This happens more easily if other vulnerability factors are reduced - if we’re not exposed to bright screens, if caffeine was stopped early in the day.
Between 10 PM and 2 AM, digestion slows, vital signs drop, and the body completes the majority of its reparation activities. It’s crucial to be sound asleep during this time, because growth hormone secretion is highest around 11 PM. By the end of this entire window, the body begins to circle back around and reduce its melatonin secretion while slowly ramping up cortisol to start the process all over again come morning.
Sleep Ranges by Age
Newborn: 0-3 months - 14 - 17 hours
Infant: 4-12 months - 12 - 16 hours per 24 hours including naps
Toddler: 1-2 years - 11 - 14 hours per 24 hours including naps
Preschool: 3-5 years - 10 - 13 hours per 24 hours including naps
School Age: 6-12 years - 9 - 12 hours per 24 hours
Teen: 13-18 years - 8 - 10 hours per 24 hours
Adult:
18-60 years - 7+ per night
61-64 years - 7 - 9 hours
65+ years - 7 - 8 hours
Other Symptoms and Sleep - respiratory system
Respiratory & circulatory systems
-respiration rate decreases
-decreases heart rate
-deep restful breaths
-blood pressure lowers
Other Symptoms and Sleep - nervous system
nervous system
-internal body temperature drops
-brain wave patterns change from more active to more relaxed
-muscle paralysis
-brain shrinks by 60%
-hormones balance for mental health
