Biological Rhythms and Sleep

Circadian 

Latin. 24hrs. SWC. Facillitated by time checks and reg events like meal times. Controlled by EP working as body clock. 

Siffre, Aschoff&Weber 

- Czeisler: dim light 13>65

- Siffre dep so no repeat 

- A&W only students so can't gen 

Infradian 

More than 24hrs. Menstural cycle. Pituitary gland releases hormones > egg ripened > oestrogen released > if no sperm womb lining sheads.

Russell et al: donors' underarm sweat to upper lips female Ps. Menstural cycles synced. Pheremones in sweat act as EPs. 

+ supported by nun studies + evo significance in allowing women who live together to coincide pregnancies, sharing childcare duties 

Ultradian 

Less than 24hrs. Cycle of brain activity during sleep. 

Dement and Kleitman - 90% ps awoken during REM reported dreaming comp to only 7% awolen in NREM. Shows diff stages. 

+ support from Reschstaffen and Kales diff patterns of activity at diff times 

+ development of EEG gives objective measument 

- artificial sleep labs 

EPs in control of Circ

Main EP = SCN nucleus. small group of cells in hypothalamus generating circ rhythm reset by light entering eyes, Rhythm produced from interaction of proteins, producing biological clock. 

Morgan: removing SCN cells from hamsters made circ rhythms disappear, but returned when = cells transplanted in. Illustrates role of SCN as EP. 

+ adaptive advantage in animals having EP reset by EZs keeping them in tune with day night changes. 

EZs in control of Circ 

Zeitgiebers such as light help reset circ, EPs respond to EZs, coodinating behaviours regulated with external environments. 

Klein: blind man with circ of 24.5hrs got out of sync with 24hr day. Took med to regulate SWC. Suggests light acts as exogenous time cue. 

- case studies lack generalisability 

Disruption: jet lag 

Upsets cood bw EPs and EZs. usually adjust slowly, but negative effects if too fast. sleepy during day, restless at night, depression, irritability, appetite loss. Phase delay less severe bc easier to adjust if ahead local time. 

Retch et al: analysed US baseball teams over 3yrs. Eastern teams did better against teams in the west than vice versa. Shows phase advance has more severe consequences. 

+ support from Klein et al: adjustment easier on Westbound flights whether homebound or outbound. 

+ a lot of naturalistic field studies in area: high in ecological validity 

but 

- many confounding variables, making establishment of causality problematic. 

Disruption: shift work

decreased alertness: night workers experience circ trough around midnight when low cortisol levels and 4am when body temp low. (Bovin) Increase stress and sleep problems. 

Phase delay system of moving shifts forwards in time, and giving adjustment period reduce negative effects. 

Knuttson: if do shift work for more than 15yrs = 3x more likely cardiovascular problems

Martino et al: linked to organ disease 

+ impetus for further reasearch ie Sharkey (melationin reduce negative effects); Czeisler: phase…