Sleep-Wake Cycle Flashcards
Delayed sleep wake disorder/ delayed sleep onset
A phenomenon that occurs in adolescence. Characterised by a shift forward of the normal onset time of the sleep period. Resulting in sleepiness at a later time. Particularly dangerous because adolescents need far more sleep than an adults. This can become a circadian phase disorder which causes extreme difficulty falling asleep and sleepiness when waking in the morning.
Circadian phase disorder
A sleep disruption caused by the alteration of an individual’s internal circadian rhythm, which can be characterised by an inability to fall asleep or remain asleep.
Melatonin
A hormone that helps to induce sleep.
Jet lag
A sleep disorder that caused by a disturbance to the circadian rhythm. Results in extreme tiredness and other physical effects. Felt by a person after a long flight across different time zones. It can take days for our body clocks to resynchronise to the new day/night time zone. Causes being awake and being tired at the wrong times, and many other sleep deprivation effects .
Shift work
Refers to only working night shift, only working early morning shifts or working rotating shifts. Most people who do shift work experience sleep deprivation effects. For some shift workers, these effects are an ongoing problem that interferes with work, family and/or other aspects of life.
Sleep wake cycle
A 24.2 (approx) - hour biological pattern that is a regular circadian rhythm. Consists of alternating sleep and wakefulness. It is determined by an internal body clock located in the hypothalamus. This clock also regulates our level of arousal, metabolism, body temperature and hormone secretions.
Sleep-Wake shift
A phenomenon that is characterised by a change in the normal onset of sleep commonly caused by adolescence, shift work and jet lag.
Causes of circadian phase disorders 5
– lifestyle factors
– genetics
– shift work
– jetlag
– adolescence, etc..
2 things that circadian phase disorders can result in
– insomnia
– impairment in social and occupational functioning.
5 lifestyle factors that effect the sleep wake cycle.
- Stressful or low stress job
• Active or inactive lifestyle - Shiftwork
- Diet and health (stimulants)
- Good sleepers are more likely to have a more regular sleep routine than poor sleepers.
Genetic factors that effect the sleep wake cycle
Studies found identical twins have more similar sleep patterns then fraternal twins. Studies also suggest females tend to need more sleep than males.
Why does delayed sleep onset occur
Melatonin is a hormone that helps to induce sleep. During adolescence the release of this hormone is delayed for up to 2 hours. Melatonin release is controlled by circadian rhythms but can also be effected by light. It is also thought social factors can impact (e.g. homework demands, after school activities, internet).
Treatment of circadian phase disorders
Light therapy can be used to re-set the body’s internal clock. During light therapy your eyes are exposed to intense but safe amounts of light for a specific and regular length of time as artificial light may be used to affect the body clock in the same way that sunlight does.
Coritsol and melatonin
Hormones regulated by the suprachiasmatic nucleus. Cortisol levels link with our level of alertness, with higher levels associated with greater alertness. Melatonin, a sleep hormone, causes sleepiness and is released when it is dark. It is secreted from a small structure in the brain called the pineal gland. Light stops melatonin secretion and therefore light can prevent sleepiness.
Zeitgeners
external (environmental) cues, such as light and dark, partially in uence the sleep–wake cycle. Such cues are known as zeitgeners.
