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Presentation on theme: "PSYA3 Revision BIOLOGICAL RHYTHMS & SLEEP Part 2: Sleep."— Presentation transcript:


2 Syllabus Biological Rhythms Circadian, infradian, and ultradian rhthyms, including the role of endogenous pacemakers and of exogenous zeitgebers in the control of circadian rhythms Disruption of biological rhythms, for example shift work, jet lag Sleep The nature of sleep including stages of sleep and lifespan changes in sleep Functions of sleep, including evolutionary and restoration explanations Disorders of Sleep Explanations for sleep disorders, including insomnia, sleep walking and narcolepsy

3 NATURE OF SLEEP MUST BE ABLE TO – Outline the different STAGES of sleep and say how they are different (brain wave activity, bodily changes) – Explain how sleep changes across our LIFESPAN SHOULD BE ABLE TO – Make reference to brief, general evaluative comments

4 NATURE OF SLEEP 5 Stages 1: Theta waves make an appearance. Myoclonic Jerks. Person is easy to wake 2: Theta Waves Dominate. Sleep Spindles and K Complexes 3: Delta Waves appear 4: Deepest sleep. Dominated by delta waves. Respiration rate lowest REM: Beta and Alpha waves (resembles being awake). Dreaming. Rapid eye movement (linked to dream content). Gradually extends in length each cycle Sleep Staircase (1->2->3->4->3->2->REM… etc) Full cycle takes approx. 90minutes SLOW WAVE (Deep) SLEEP NREM SLEEP

5 Lifespan Changes OHAYON (2004) meta analysis of sleep studies found… – Total sleep time decreases as we get older (470mins at age 5 ; 370 mins at age 70) – Deep sleep (3&4) % decreases (25% -> 9%); may be linked to restoration? – REM sleep % decreases (25% -> 20%); may be linked to memory consolidation? – Adolescents sleep more at weekends and less during the week; may highlight the influence of EZs on sleep? EVALUATION – Objective measures used (e.g. brain scans) – But as it is a meta analysis we cannot be sure ALL studies are conducted under controlled, scientifically rigorous conditions; difficult to compare results – Individual differences need to be taken into account; careful not to make nomothetic, deterministic conclusions

6 FUNCTION of Sleep MUST BE ABLE TO – Discuss restoration theory of sleep – Discuss evolutionary theory of sleep

7 Functions of Sleep - Restoration AO1 Sleep serves important restorative functions NREM (especially slow wave sleep) important for bodily repair and growth (release of growth hormones, protein synthesis etc) REM important for neural (brain) repair and growth (neurogenesis, replenish neurotransmitters, etc) as well as cognitive development (e.g. memory consolidation) AO2 / 3 Evidence – Case Studies of Sleep Deprivation (Tripp, Gardner, Fatal Familial Syndrome) Ethical BUT have to be careful as they are case studies (generalisation issues) – Recthshaffen – Rats on a turntable – all died! Ethical BUT problems with extrapolation – Shapiro – Athletes sleep longer following periods of exertion – Ohayon – babies sleep for longer and have more slow wave and REM sleep; makes sense as babies are growing rapidly and developing cognitive skills rapidly. – Horne and Minard – CONTRADICTS; PPTS did not sleep longer following periods of exertion

8 Functions of Sleep - Restoration General Evaluation Scientific and objective due to use of rigorous methods Biologically Reductionist – sleep serves other important functions so we need to look at other theories for a complete picture (e.g. evolutionary theories – briefly outline) Individual Differences need to be taken into account

9 Functions of Sleep - Evolutionary AO1 Sleep is universal so it must be ADAPTIVE Ecological Niches shape the nature of sleep Sleep is adaptive because it causes energy conservation Sleep may protect animals when they are most vulnerable Sleep may be linked to foraging (herbivores sleep less because they need to spend more time eating to gain the required nutrients) Sleep linked to predator – prey status of the animal (prey sleep less as they are more vulnerable) AO2 / 3 Evidence from the ANIMAL KINGDOM (sloths, lions, sheep) – BUT association NOT cause and effect – Artificiality of animal studies as many are conducted in controlled environments like zoos – does this reflect ‘normal’ sleep patterns – Some exceptions (e.g. sloths) Non reductionist theory – takes into account the whole animal and their lifestyle instead of concentrating just on, say, physical restoration. – BUT does not allow us to identify the MOST IMPORTANT factor which determines sleep patterns Face Validity Unfalsifiable due to the evolutionary nature of the theory Alternative theories (e.g. restoration) should also be considered to give us a complete / detailed view of the function of sleep

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