The Importance of Sleep Flashcards
What is the purpose and function of sleep?
repairs
flushes away waste
dna repair
What is the ‘restoration theory’ ?
the concept that needing to sleep correlates to the body and minds need to repair and energise (physiological rest)
When asleep, large/small muscles in the body are relaxed, functions such as heart and breathing rates slow down, and the rate of neural activity in various brain structures can be reduced
Growth hormones are also secreted at a much higher rate when asleep
What are our biological rhythms?
Circadian - sleep/wake cycle (24 hours)
Ultradian - REM and NREM sleep cycles (under 24 hours)
Infradian - Menstrual cycle, seasonal factors, animal migrations (more than 24 hours)
What is the ‘circadian rhythm’ ?
A 24 hour body clock that regulates sleeping and waking around day/night
This cycle is determined by an internal body clock ‘the suprachiasmatic nucleus’
Levels of arousal, hormone secretions, metabolism, heart rate and body temperature are largely influenced by the SN
For most of us, the circadian cycle peaks (awake and alert) during the day, with the lowest point being early in the morning (drowsy and sleepy).
How does our circadian rhythm body clock work?
Our sleep wake cycle is influenced by internal and external factors
Environmental cues (light/dark) can influence the sleep-wake cycle, this is known as zeitgebers
our body clock has a 24.2-25 hour cycle
This means that our natural sleep–wake cycle is slightly longer than 24 hours.
What is the suprachiasmatic nucleus ?
located in the hypothalamus in the brain
our bodies ‘clock’ that regulates the sleep-wake cycle
regulates hormones cortisol and melatonin
detection of light is the primary external signal for the suprachiasmatic nucleus
What does the hormone melatonin do?
The sleep hormone, causes sleepiness
released in the Pineal Gland
dark triggers it to be released, light stops it’s production
Adrenalin is also involved, influencing blood pressure and heart rate
What are the effects of light on sleep?
Exposure to light at different times in the day has different effects
Early morning light can cause us to wake up
Light in the evening causes a phase delay by keeping us awake
Light sensors in our eyes/knees inform our brain when it is light, which then adjusts our internal body clock to match it
How does evolution come into the circadian theory?
circadian cycle suggests humans have evolved to sleep in the dark as a survival mechanism
we have bad night vision, higher risk of attack/injury so we sleep at night to stay safe
What’s the difference between the evolutionary (circadian) theory and the restoration theory?
