Biological Rhythms - Rhythms

Ultradian
1. Sleep - The sleep cycle. There are 5 phases of sleep that form a sleep cycle. Most people experiance 5 complete cycles each night, each cycle lasting from 90 to 110 minutes.
  1. Stage 1 - Light sleep; eye and muscle activity decreases by 50%; sleeper may experience sudden muscle contractions.
  2. Stage 2 - Eye movement stops; muscle activity stops; brain waves slow; sleep spindles (small bursts of brain activity) begin.
  3. Stage 3 - Deep sleep starts; brain begins to produce very slow delta waves; no eye or muscle movement; difficult to wake the sleeper.
  4. Stage 4 - Deep sleep; brain produces only delta waves; no eye or muscle movement; sleeper may be disoriented if awakened.
  5. REM - Heart and breathing rates increase; eye movement is quick and irregular; blood pressure rises; breathing becomes shallow; muscles of the chin, neck, torso and limbs are paralyzed; sleeper begins to dream.
  6. Dement and Kleitman (1957) - Link between REM sleep and dreaming. Woke up pps at times when their brain waves showed characteristics of REM sleep and found pps were highly likely to report dreaming. They did find though that dreams were also reported outside of REM sleep and that some pps when awoken from REM did not report dreaming so this shows individual differences. - Lab studies are low in ecological validity.
  7. Jouvet (1972) - Found that destruction of an area just below the locus coeruleus in the brain stem of cats permanently destroyed their REM sleep. Newer technology shows certain neurons critical for REM sleep such as cholingeric cells are found in this area. Ethics - was it stress that influenced results?
  8. NREM - N1 light sleep, noises wake you up. N2 40-50%. N3 DELTA - slow wave sleep. 90 minute cycle.
2. Urine Flow - Mandell et al (1966) - Catheterised seven male pps and measured urine flow over 11 nights. All periods of REM sleep were associated with change in urine flow. Within 2 minutes of REM urine flow decreases significantly and at the end of REM sleep urine flow increases once more. - The findings may not be replicated though as the change in urine flow in males could be due to penile erection during periods of REM sleep, this is known to slow urine flow.
Circadian
1. Endogenous Pacemaker
  1. The SCN (Suprachiasmatic nuclei)
    1. Controls the sleep wake cycle. Light enters the eye. Information passes through the optic nerve. As the nerves cross paths the SCN is located. SCN detects the level of light. *Light diminishing - SCN activates the pineal gland, secreting melatonin, inducing sleep. *Light increasing - pineal gland inhibits production of melatonin, coupled with cortisol the person begins to wake up.
    2. Ralph et al (1990) - Took SCN fro golden hamsters that had mutated SCNs of 20.2 hrs. Transplanted into non-mutated hamster. Their circadian rhythms had shortened to that of the donor SCN. (Further research shows the individual cells within the SCN have different rhythm lengths from 21.25-26.25 hrs, Liu et al (1997) believes this corresponds to ave rhythms across a large number of SCN cells the ave 24hr rhythm. - Can't be generalised to humans (physiological differences) HOWEVER, the biological approach would disagree - there are many physiological similarities across mammals, generalise with caution. Ethical issues worth the result?
  2. Michel Siffre - Spent 3 extended periods in caves, the longest being 1972 Midnight Cave which lasted 205 days. Didn't have access to a clock but could illuminate his living quarters when he wished. At first his sleep pattern was erratic but soon settled into a regular free-running rhythm, day shift to 25 hours. - Case study, cannot be generalised (no population validity, doesn't account for cultural or individual differences). Two IVs, light + activity. Not reliable, only done once. Artificial light can reset the time clock - found by Dement.
  3. Aschoff et al. - Pps spent up to a month in underground laboratories (to shield the pps from external factors that would allow them to know the time). Pps were able to sleep + complete activities when they wanted. Appeared to keep a regular cycle of daily activities, their cycles did begin to drift though. After 2 weeks most pps were half a day out. The bodies natural rhythm = 25 hrs. Sleep wake cycle becomes free running being controlled by internal factors. - Social influences, not isolated. Not ecologically valid but better than Siffre due to activities, but easier to generalise due to more pps. (Entrainment - being put back into time).
  4. Campbell & Murphy (1998) light on back of knees - Light can enter the body through our skin. Sleep lab with artificial light. 15 volunteers took part in 33 trials lasting 4 consecutive days and nights. On the 2nd night of each trial half the pps had light shone on the popliteal region for 3 hrs. (Area rich in blood). Compared to the control group the core body temp + melatonin production shifted up to 3 hrs. They believe light sensitive haemoglobin have an influence on melatonin. - Flawed, pps eyes were not stopped from seeing the light, when this variable was rectified melatonin levels did not shift like the first study.
2. exogenous zeitgebers
  1. Light (external factor to tell the time of day)
Infradian
1. Menstrual cycle
  2. On days 1 to 5 is menstration which is where the womb lining is shed. On the 5th day FSH is released, travelling to the ovaries where the egg begins to develop. On day 7 the egg signals the ovaries. The ovaries produce oestrogen. Lining of the womb will build up again. Days 13 to 15 is ovulation which is where the egg is released from the ovary. On day 15 the brain stops producing FSH and starts producing LH. LH triggers ovulation which releases the egg.
  3. McClintock 1972 - 135 women ages 17-22 years living in all female halls of residence. Asked to recall previous menstrual cycles over the previous year, how much time they spent each week in male company and with females they considered their best friends and spent the most time with. Women who spent the most time with each other had synchronised cycles. - Further research found a significant degree of synchronisation of mothers and daughters residing in the same home (+women who work together, among women's basket ball teams and in lesbian couples). - opportunity sample, high in ecological validity.
  4. Russell et al 1980 - Could olfactory cues from one woman influence the timing of menstruation in another. Collected odour by placing cotton pads in the armpits of donors for 24 hours. The donors were told not to wear deodorant or wash their armpits during this time. The cotton wool pad was then rubbed on the upper lips of pps who were told not to wash their faces for 6 hrs. This happened 3 times a week for 6 months. Menstrual cycles shifted significantly to resemble the donors cycle. - Shows that exogenous factors can effect endogenous pacemakers greatly. Volunteered sample, demand characteristic. Evolutionary theory, advantage to species as babies can be mothered by other mothers.
2. SAD
  1. Similar to depression - absence of natural sunlight: feeling irritable, stressed, sleep more.
  2. Winter Blues: amount of sunlight that you get can affect your: mood, appetite, energy level, sex drive.
    1. Summer: Temperature, activity, more social, exercise more.
  3. Eastman et al (1998) - Treated pps either with a bright light (6000lux) or a placebo. Bright light pps were more likely to respond with partial or full remission of symptoms. Postolache et al (1998) - treatment isn't effective in the summer. When light therapy is given equally in the summer and winter months, depressive symptoms are still higher in the winter.

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Biological Rhythms - Rhythms

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	Created by rowanechapman about 8 years ago