Biological Rhythms
Circadian, Ultradian and Infradian Rhythms.
Jet lag and Shiftwork
- Created by: Jodie-Leigh
- Created on: 30-05-14 19:14
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- Biological Rhythms
- Circadian
- 24 hour period
- Sleep-wake cycle regulated by melotonin released by pineal gland when dark
- Rats - SCN removed, abolishing SW cyle
- Genetically bred hamsters - 20hr circadian rhythms, SCN transplanted into 'normal' rats, who then developed 20hr rhythm
- Siffre - 6 months in cave, scientists called to turn lights on and off. He recorded BP, and a series of mental, memory, and physical tests.
- 1st month - 26hr cycle, suffering from loneliness and depression. 6th month - eye sight worsened, had physical and mental troubles.
- ? Useful - blind people and astronauts.
- Support: WW2 bunker - no enviromental cues, most had cycle of 24-25hrs (some had 29hrs)
- X Not representative - people have different biological rhythms
- Support: 12 ppts, 3 weeks, slept 11:45pm to 7:45am. Clock changed from 24 to 22hrs. Ppts stayed at 24 hours
- Deterministic
- Supports the biological approach
- Support: Blind man - extraneous factors such as clocks, but still had little effect on making it difficult for him to function
- Ultradian
- Stage 1: Light sleep, muscle activity slows down
- Stage 2: Breathing and heart rate decreases
- Stage 3: Deep sleep, braid generates slow delta waves
- Stage 4: Very deep sleep, little muscle activity, lots of brain delta waves
- Stage 5: REM, dreaming, very active brain
- Stage 4: Very deep sleep, little muscle activity, lots of brain delta waves
- Stage 3: Deep sleep, braid generates slow delta waves
- Stage 2: Breathing and heart rate decreases
- 9 ppts wired to EEG (measures brain activities). Ppts woken when patterns changed and reported what they were experiencing.
- 80% during REM reported dreaming
- 20% during NREM reported dreaming
- REM dreams were more intense
- Deterministic - no control over sleeping patterns
- Less than a day
- Stage 1: Light sleep, muscle activity slows down
- Infradian
- Longer than 1 day
- Controlled mainly by hormones - endogenous, secreted by the pineal gland so is influenced by day light
- 10yr long stud, 29 women (20-35yrs) with history of irregular periods.
- Samples of pheromones from 9 of these at certain points of menstruation (cotton pads), pads then wiped under noses of 20 others daily. 68% women's periods change in response.
- Many exogenous factors such as stress, diet and other women who are living with them
- SAD - has seasonal pattern. Suspected link to reduced sunlight.
- Light stimulates the hypothalamus which controls mood sleep and appetite. Lack of sunlight prevents it from working properly.
- Deterministic- Severe PMS - mental disorder - effects law
- Light therapy - sufferes report that daily use of light box reduces symptoms
- Jet Lag
- Body's effected by sudden time changes - takes the SCN several cycles to sinc.
- Winter et al calculated that for every hour time difference it takes 1 day to recover.
- Symptoms: Insomnia, mild depression, fatigue, and performance effects
- East to West = phase delay (causes less jet lag)
- West to East = phase advance (causes more jet lag)
- Going to bed earlier is easier than staying up later
- East to West = phase delay (causes less jet lag)
- Going to bed earlier is easier than staying up later
- Baseball players. 3hr time difference. When west went to east won 44% of the time. When East went to West they won 37% of the time.
- Awake during circadian trough - disrupts rhythm
- Shift Lag
- Causes de-synchronisation of the body clock
- Midnight = lowest cortisol levels.
- 4am = lowest core body temperatue
- Causes sleep deprivation - 1-2hrs less sleep in the day. Particularly effects REM
- 3 Times increased risk of heart disease when working more than 15yrs on night shifts.
- Social disruption leads to higher divorce rates
- Rotating shifts (alternating daily) are more harmful than non-fluctuating shifts (which disturbs the biological rhythm less)
- Forward roatating shifts change every 3-4 days (6am-2pm, 2pm-10pm, 10pm-6am). Easier to adjust- better work/social life.
- 10 studies reviewed. Melatonin successful in helping ppts sleep when taken daily.
- 31 males exposed to very bright, bright, normal and dim light. Circadian rhythm adjusted by +5hrs, +3hrs, +1hr, and -1hr.
- Decreased disasters
- Circadian
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