Lesson 12 - Biological Rhythms Flashcards
Infradian Rhythms
Last longer than 24 hours e.g. menstrual cycle and seasonal affective disorder.
The Menstrual Cycle
Regulated by hormones promoting ovulation or stimulating the uterus for fertilisation. Halfway through ovulation begins, after the ovulatory phase, progesterone increases in preparation for a possible embryo.
When Does Ovulation Begin
When oestrogen is at its highest (halfway through).
Menstrual Cycle Strengths
Cave Study
Cycle Based On Odour
Feminised Faces
Cave Study (+)
Reinberg - Examined woman who spent 3 months in a cave with only a small lamp, causing her cycle to shorten to 25.7 days meaning it’s affected by light.
Cycles Based On Odour etc (+)
Russel Et Al - Found cycles can syncrhonise based on odour, sweat samples of one group were rubbed on the upper lip of another group and despite being separate they synced - external factors should always be taken into consideration.
Feminised Faces (+)
Penton Volk Et - Found woman had a preference for feminised faces at the least fertile stage of the cycle and men at the most fertile meaning it affects sexual behaviour.
Seasonal Affective Disorder
Where there’s season variation in mood. It’s a yearly cycle and melatonin is partly responsible.
Example Of Seasonal Affective Disorder
Depressed in winter
How Is Melatonin Responsible
A lack of light in winter results in increased melatonin, which is linked to depressive systems.
Seasonal Affective Disorder Strengths
Country Validity
Practical Application
Country Validity (+)
Terman - SAD is more common in countries where winter nights are longer. 10% of people in North USA and 2% in South USA suffered from SAD, showing it’s selected by light and therefore melatonin.
Practical Application (+)
Phototherapy cures SAD, it rests melatonin levels which regulates serotonin and improves symptoms for 60% of patients.
Seasonal Affective Disorder Weakness
Placebo Affect
Placebo Affect (-)
30% of participants showed improvements with a pretend ‘negative generation’, suggesting phototherapy may just work due to the placebo affect.
Phototherapy
A Lightbox that stimulates strong levels of light in the morning and evening to regulate melatonin levels.
Exogenous Zeitgebers
External factors/cues affecting internal biological rhythms.
Ultradian Rhythms
Are less than 24 hours, and can be found in human sleep patterns.
The Human Sleep Cycle
Alternates between REM & NREM, the cycle goes light sleep –> deep sleep –> REM sleep and circles every 90 mins.
REM Sleep
Where brain waves speed up and dreaming occurs.
Stages Of Sleep
1 & 2 = Light Sleep
3 & 4 = Deep Sleep
5 = Rem Sleep
1 & 2 - Light Sleep
Brain wave patterns are slower and more rhythmic, starting with alpha and ending with theta waves.
3 & 4 - Deep Sleep
Slow waves, associated with deep waves.
5 - REM Sleep
It’s difficult to wake someone up, associated with slower delta waves
BRAC
Basic Rest Activity Cycle
Kleitman
Referred to the 90 minute sleep cycle as BRAC, which continues when you’re awake instead of sleeping going from alertness to psychologically fatigued.
Ultradian Rhythms Case Study
Dement & Kleitman studied brain activity of 9 adults using EEG in a sleep lab, alcohol and caffeine was controlled, EEG patterns within each sleep stage, correlated with dreaming.
Potential Issue With Dement & Kleitman
The study has a small sample size but the results have been replicated suggesting there’s a reliable link.
Ultradian Rhythms Strengths
Research Support
Pianists
Research Support (+)
Dement and Kleitman’s study
Errisson Et Al (+)
Found a group of elite violinists practice for 90 mins and slept after, the best ones sleeping longer, supporting the BRAC.
Ultradian Rhythms Weaknesses
Difficult To Generalise
Difficult To Generalise (-)
Tucher Et Al studied participants over 11 days and each sleep stage had different characteristics suggesting there’s possibly biological differences that influence the study.
