CHAPTER 6 Sleep pages Flashcards
Circadian rhythms
daily biological cycles
Most circadian rhythms are regulated by the brain’s
superchiasmatic nucleus (SCN)
SCN neurons have genetically programmed cycle of activity and inactivity, functioning like a biological clock
They link to the tiny pineal gland which secretes melatonin
what secretes melatonin?
pineal gland
melatonin
a hormone that has a relaxing effect on the body
SCN neurons become active …..and are inactive when …
during the day SCN neurons become active during the daytime and reduce the pineal gland’s secretion of melatonin, raising body temperature and heightening alertness. At night, SCN neurons are inactive, allowing melatonin levels to increase and promoting relaxation and sleepiness
The eyes have a neural connection to the
SCN and after a nights sleep, the light of day increases SCN activity and helps reset your 24 hour body clock
In experiments where people could not tell whether it was day or night outside drifted into a
free running circadian rhythm which is longer than 24 hours
Environmental changes can disrupt our ….
circadian rhythms
Fly east vs flying west
Flying east, you lose hours from your day and flying west, extends your day to more than 24 hours
the body naturally adjusts about one hour or less per day to time-zone changes
typically people adjust faster when they are flying west, presumably because lengthening the travel day is more compatible with out natural free-running circadian cycle
Night shift work
Daytime becomes bed time and you may sleep less than you did before
Night shift body clock is promoting sleepiness
Over time you may become fatigued, stressed and more accident prone
On days off, reverting to a typical day-night schedule will disrupt any hard-earned circadian rhythm adjustments you have made
Seasonal affective disorder
a cyclic tendency to become psychologically depressed during certain seasons of the year
in cooler climates, SAD tends to begin in autumn or winter, when there is less daylight, and then shifts to spring
Sensitive light, so use light therapy
Beta waves
when you are awake and alert
Alpha waves
feeling relaxed and drowsy, your brain wave slow down
What happens roughly every 90 minutes whilst asleep?
we cycle through different stages in which brain activity and other physiological responses change in a generally predictable way
As sleep begins…
brain wave pattern becomes more irregular and slower theta waves increase and you are now in stage 1, a form of light sleepf rom which you can easily be awakened. Probably spend just a few minutes in stage 1 during which some people experience dreams, vivid images and sudden body jerks
As sleep becomes deeper
sleep spindles which are periodic 1- to 2- second bursts of rapid brain wave activity begin to appear. Sleep spindles indivate that you are now in stage 2. Your muscles are more relaxed, breathing and heart rate are slower and you are harder to awaken
As sleep becomes even deeper…
Sleep deepens as you move to stage 3, marked by the regular appearance of very slow and large delta waves. As time passes, they occur more often and when delta waves dominate EEg pattern you have now reached stage 4 sleep. Collectively termed slow wave sleep. You body is relaced, activity in various parts of the brain has decreased, you are hard to awaken and you may have various dreams
together stage 3 and 4 sleep are often referred to as
slow wave sleep
After 20-30 minutes of stage 4 sleep…
your eeg pattern changes as you go back through stages 3 and 2, spending a little time in each. Overall, within 60-90 minutes of going to sleep you have completed a cycle of stages : 1-2-3-4-3-2. At this stage a remarkably different sleep stage ensues …REM sleep
REM Sleep
Characterised by rapid eye movements (REM), high arousal and frequent dreaming
ALthough each cycle through sleep takes an average of 90 minutes, as the hours pass, stage 4 and then 3 drop out and REM periods become longer
REM sleep decreases dramatcally during
infancy and early childhood but remains relatively stable thereafter
Randy Gardener
Stayed awake for 11 days
first few days - became irritable, forgetful and nauseated
by the fifth day - periods of disorientation and mild hallucinations
last 4 days - finger tremours and sleered speech
when randy finally went to be he slept for almost 15 hours the first night and returned to his normal amount of sleep within a week
in general, it takes several nights to recover from extended sleep deprivation and we do not make up for all the sleep time that we have lost
Many researchers believe that the sleep stages help us
remember important information by enhancing memory consolidation, a gradual process by which the brain transfers information into long term memory
Insomnia
Refers to chronic difficulty in falling asleep, staying asleep or experiencing restful sleep
Narcolepsy
involves extreme daytime sleepiness and sudden, uncontrollable sleep attacks that may last from less than a minute to an hour
Antidepressent drugs suppress
REM sleep
