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Circadian Rhythms and Sleep - Coggle Diagram
Circadian Rhythms and Sleep
Circadian Rhythm
Cycle of behavioural or physiological changes that occur over a 24 hour period. Eg body temp, secretion of hormones.
Controlled biologically by:
Supra-chiasmata nuclei (SCN)= group of pacemaker cells in the hypothalamus in the brain.
Pineal Glands- Glands in the brain that secrete the hormone melatonin which causes sleepiness.
Amount of light exposed to can alter our circadian rhythm.
A zeitgeber is any external or environment cues that entrains or synchronises an organism's biological rhythms to the Earth's 24-hour light/ dark cycle and 12 months cycle.
Entrainment occurs when rhythmic physiological or behavioural events match their period and phase to that of an environmental oscillation.
Desynchronization
Occurs because external cues (exogenous) are altered compared to internal cues (endogenous).
Sleep
Periodic state that alters awareness and is accompanied by physiological effects.
Each night we go through several stages of sleep.
Each stage is characterised by different brain waves and features.
Brain waves are measured by an EEG (electroencephalogram).
Stage 1 Sleep:
Light sleep
Heart rate slows, breathing slows down, muscles start to relax.
Hypnogogic sensations- often the hallucinations of floating, 'see' flashing lights or colous.
Brain waves start to show theta patterns.
Can be easily woken
Stage 2
Lasts about 20 minutes
Body temp starts to drop, heart rate and breathing slow.
Sleep Spindles (short bursts of activity) appears in the brain waves
K complexes- suppress arousal in response to stimuli
Theta waves (large and frequent waves) appear
Stage 3 Sleep
Delta Waves (large and slow) appear signalling deep sleep.
Breathing, heart rate, blood pressure, body temp continues to drop.
Stage 4
Deepest level of sleep
Pure delta waves
Stage 3 and 4 called Slow Wave Sleep
Breathing, heart rate, blood pressure, body temperature continues to drop.
Hard to wake
REM Sleep
After stage 4
Person moves into REM Sleep- Sequence then reverses
REM- Rapid Eye Movement
EEG shows activity of an awake person (fast short beta waves)
Pulse rate, blood pressure quicken, respiration faster, easy to awaken
Muscle paralysis (relaxation)
Vivid dreams with complex plots
Sleep Needs
Sleep patterns change with age
On average most young adults need 8 hours of sleep per night and have approximately 4 cycles of sleep per night.
Babies sleep more and have more REM sleep than adults.
As you get older the amount of time in Stage 1 sleep increases and time in slow wave (stage 3 and 4 ) decreases.
Why do We Need Sleep
Repair- restoration theory: Sleep helps us recover from the activity of the day.
Evolutionary - circadian theory: Sleep evolved so animals could conserve energy when they were not finding food or seeking mates.