Biological rhythms

Task 1 Outline what is meant by biological rhythms (2 marks) Biological rhythms are cyclical changes in the way biological systems (humans, animals, plants) behave (1 mark) . One of the most obvious is the sleep-wake cycle. In adult humans for example, we will typically spend approximately 16 hours of every 24 hour cycle in consciousness, and 8 hours of every 24 hour cycle in varying degrees of unconsciousness. In other words, we spend about one third of our day sleeping (although individual differences vary greatly) and two-thirds awake (2 marks) 1 mark for accurate description and 1 mark for elaboration

Task 2 On flash cards, in detail define what is meant by. Also give an example of each Exogenous zeitgebers Endogenous pacemakers Circadian rhythms Infradian rhythms Ultradian rhythms 2) Test and retest your friends for five minutes

Task 3 Identify the correct definitions on the work sheet Answers: a) A rhythmical change that occurs approximately every 24 hours to complete – Circadian Rhythms b) Factors from the environment that influence biological changes in rhythms – Exogenous Zeitgebers c) A rhythmical change that take fewer than 24 hours to complete - Ultradian Rhythms d) Biological factors that set our rhythms – Endogenous pacemakers e) A rhythmical change that take more than 24 hours to complete (for example, monthly) – Infradian Rhythms

Task 4 – Circadian Rhythms Place these items into endogenous and exogenous groups Melatonin Sunrise Pineal gland Suprachiasmatic Nuclei (SCN) Darkness IPad Serotonin Protein production Alarm Clock Smell of toast

Task 5 Re-read page 23 in the pack and remind yourself of the biological process of sleep and waking Use these words to explain the role of endogenous pacemakers in sleep Protein Production Melatonin Pineal gland SCN Causes drowsiness threshold

Task 5 On the BWBs, draw a picture that plots the endogenous pacemakers involved with the sleep-wake cycle

Task 6 Fill in the gaps to explain how exogenous zeitgebers affect the sleep-wake cycle

Task 6 Now add the Exogenous Zeitgebers to your picture

Looking at the mark schemes You will be shown three answers to a question. Use the mark scheme to decipher the level and mark you would award “Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks)” Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) – Alan’s Answer Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none Different things influence sleep. Our internal clocks are regulated by the SCN which releases melatonin. Melatonin makes us sleep whilst the sun and other environmentals will wake us up

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) – Alan’s Answer Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none Different things influence sleep. Our internal clocks are regulated by the SCN which releases melatonin. Melatonin makes us sleep whilst the sun and other environmentals will wake us up Alan gets a level 4 – 1 marks.

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) - Jemima’s answer Both endogenous pacemakers and exogenous zeitgebers (external cues) help to maintain and control the sleep waking cycle. Endogenous pacemakers are internal ‘biological clocks’ that manage our rhythms. The main pacemaker in mammals is the Suprachiasmatic Nuclei (SCN), a cluster of nerve cells located in the hippocampus which produces proteins which regulate the pineal gland. This in turn releases melatonin which causes drowsiness and eventual sleep in people. Other environmental factors, such as light also play a regulatory role Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) - Jemima’s answer Both endogenous pacemakers and exogenous zeitgebers (external cues) help to maintain and control the sleep waking cycle. Endogenous pacemakers are internal ‘biological clocks’ that manage our rhythms. The main pacemaker in mammals is the Suprachiasmatic Nuclei (SCN), a cluster of nerve cells located in the hippocampus which produces proteins which regulate the pineal gland. This in turn releases melatonin which causes drowsiness and eventual sleep in people. Other environmental factors, such as light also play a regulatory role One big error and not enough explanation of the role of exogenous factors. Jemima gets a low level 2 – 4 marks Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) – Jose Pablo’s answer Both endogenous pacemakers and exogenous zeitgebers (external cues) help to maintain and control the sleep waking cycle. Endogenous pacemakers are internal ‘biological clocks’ that manage our rhythms. The main pacemaker in mammals is the Suprachiasmatic Nuclei (SCN), a cluster of nerve cells located in the hypothalamus which produces proteins which in turn, regulate the pineal gland to produce the sleep hormone, melatonin. The circadian rhythm can persist without the presence of exogenous zeitgebers, nonetheless they do have a significant impact on regulating the endogenous pacemakers. The SCN detects changes in the light (daylight vs night, for example) and alters our sleep- wake cycle. Light will stimulate the SCN to produce more protein, stimulating the pineal gland to produce more melatonin which induces sleep by inhibiting the mechanisms that create wakefulness Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none

Outline the role of endogenous pacemakers and exogenous zeitgebers in one circadian rhythm (6 marks) – Jose Pablo’s answer Both endogenous pacemakers and exogenous zeitgebers (external cues) help to maintain and control the sleep waking cycle. Endogenous pacemakers are internal ‘biological clocks’ that manage our rhythms. The main pacemaker in mammals is the Suprachiasmatic Nuclei (SCN), a cluster of nerve cells located in the hypothalamus which produces proteins which in turn, regulate the pineal gland to produce the sleep hormone, melatonin. The circadian rhythm can persist without the presence of exogenous zeitgebers, nonetheless they do have a significant impact on regulating the endogenous pacemakers. The SCN detects changes in the light (daylight vs night, for example) and alters our sleep- wake cycle. Light will stimulate the SCN to produce more protein, stimulating the pineal gland to produce more melatonin which induces sleep by inhibiting the mechanisms that create wakefulness – Jose Pablo gets full marks Level Marks Knowledge Accuracy 1 6 Well-detailed Complete accuracy 2 4-5 Reasonably-detailed Rare/few inaccuracies 3 2-3 Present but lacks detail Numerous inaccuracies 4 Limited Highly inaccurate 5 None none

Task 7 and 8 Outline one research study supporting the role of both endogenous pacemakers and exogenous Zeitgebers

Exam practice

Exam mark-scheme

Further evaluation – applications of research Knowledge of this will help psychologists with what? Business and shift work (how) Researchers found that some shift work schedules leave the workers tired, susceptible to illness and inefficient, whilst other schedules improved efficiency How drugs work (how does this help?) Treating sleep disorders (how does this help?)

Infradian rhythms Fill in the gaps on the worksheet: These are rhythms that last for a period of time greater than 24 hours. The obvious example is the menstrual cycle which has a number of endogenous mechanisms regulating the cycle, although exogenous zeitgebers can impact the cycle When a baby girl is born, she has all the eggs her body will ever use, and many more, perhaps as many as 450,000? They are stored in her ovaries, each inside its own sack called a follicle. As she matures into puberty, her body begins producing various hormones that cause the eggs to mature. This is the beginning of her first cycle; it's a cycle that will repeat throughout her life until the end of menopause.

Endogenous pacemakers TASK 9 - Answers a) Hypothalamus b) Pituitary gland c) Oestrogen d) Ovulation e) Progesterone f) Menstrual flow (bleeding)

Answers to question 10 In Reinberg’s early case study, how long had the female participant been in the cave without exogenous zeitgebers? Three months How many hours had her days lengthened to? 24.9 hours How many days had her menstrual cycle shortened to? 25.7 days What conclusion can be made about exogenous zeitgebers on the regulation of infradian cycles? Suggests that infradian biological rhythms could be influenced by exogenous zeitgebers such as light In Mc Clintock and Stern’s (1998) study, which exogenous zeitgebers was thought to have influence over the menstrual cycle? Pheromone secretions from other women

Answers to question 10 What happened to the participants who inhaled the pheromones from women who were about to ovulate? menstrual cycles became shorter What happened to the participants who inhaled the pheromones from women who had just finished ovulation? their menstrual cycles became longer What conclusion can be made from this study? This explains why when a group of women live in close proximity their menstrual cycles tend to synchronise and provides support for the role of exogenous zeitgebers (pheromones) in infradian rhythms Are other findings reliable? No. So can we trust the findings from these studies? No.

Fill in the gaps – ultradian rhythms These occur more than once in a 24 hour cycle (shorter than 24 hours). Most are confined to either day or night, for example the stages of sleep. A typical night’s sleep takes you from stage 1 to 4 then back to 2 and finally into REM. This whole cycle then repeats itself three or four more times during the night, each cycle lasting about 90 minutes. The final stage or two may not contain any stage 4 sleep

The ultradian rhythms

Characteristics of ultradian rhythm (sleep stages) Characterised by hypnogogic phenomena and usually comprise of fleeting images – Stage 1 Sometimes we may wake without realising that we’ve even been asleep – Stage 1 Delta waves now constitute most of the brain activity and we are now at our most relaxed – Stage 4 This is characterised by bursts of high frequency waves called ‘sleep spindles’ – Stage 2 The brain now becomes very active, almost indistinguishable from a waking brain – REM The brain waves start to slow and we experience our first slower ‘delta waves’ on EEG readings – Stage 3 At this stage we are very difficult to wake up and even vigorous shaking may not be sufficient to wake some people – Stage 4 We are paralysed and unable to act out the brain’s bizarre thoughts - REM

Task 13 – expanding on supporting evidence Dement (1960) compared participants who had been deprived of REM sleep with a control group who had been deprived of the same amount of NREM sleep. He found that the REM deprived group were more irritable, more aggressive and unable to concentrate on various tasks. How does this support the concept of separate and distinct stages of sleep? That people changed their temper and cognitive abilities when only deprived of REM sleep means that it is an important stage in sleep, therefore it must be distinct from the other stages, as deprivation in other stages did not have the same effect Borbely (1986) found that REM deprived individuals made 31 attempts to re-enter REM on the first night of deprivation, 51 attempts on the second night and over 60 attempts on the third. This shows that REM is a distinct stage of sleep.  Because the same would have happened if sleep deprived in the other stages, but it did not, meaning there must be something very important to us with REM

Question a Ultradian rhythms are biological changes that repeat more than once in a 24 hour cycle, for example the repeated stages of sleep (1 mark) whereas Infradian rhythms are biological changes that take longer than 24 hours to complete, for example the menstrual cycle (1 mark) the menstrual cycle is regulated by hormonal changes in oestrogen and progesterone (1 mark) whereas the stages of sleep are governed by differing electrical activity (1 mark)

Question b) AO1 = 3 and AO2/3 = 5 AO1 endogenous pacemakers include the SCN, protein production, pineal gland, melatonin. Exogenous Zeitgebers include light detected by the retina (or skin), temperature changes, noise which would re-set the function of the SCN AO3 = supporting evidence to include Morgan’s hamster study (endogenous pacemakers) and Michel Siffre (exogenous zeitgebers), role for an interaction of both in sleep-wake cycle, A02 = practical applications include advising companies which use shift work