Bilogical Rhythms

A2 Psychology Revision Cards


Describe two biological Rhythms. (9)

An infradian rhythm involves a cycle greater than 24 hours. For example, the human menstrual cycle occurs every 28 days, although it can be 20–60 days. It is controlled by the hormones oestrogen and progesterone, and the target organs are the ovaries and womb. The hormones cause the release of the egg and thickening of the lining of the womb so that it is ready to receive a fertilised egg. If the egg is not fertilised the lining is shed and so menstruation is the outcome of a cycle of activity that prepares the body for conception. Menstruation is an endogenous mechanism as it is controlled mainly by internal biological factors (the hormones) but exogenous factors (external cues) can also affect the rhythm.

A circadian rhythm repeats in a cycle of once every 24 hours. The 24-hour sleep–waking cycle is a good example of a circadian rhythm because it clearly illustrates that circadian rhythms depend on an interaction of physiological and psychological processes. Our fairly consistent sleep pattern suggests an internal or endogenous mechanism—the biological clock. But this can be overridden by psychological factors such as anxiety.

1 of 18

Describe the nature of sleep. (9)

The sleep–wake cycle offers important insights into the nature of sleep such as the role of the biological clocks, the SCN and the pineal gland, and the role of biochemicals such as the melatonin released by the pineal gland when it receives electrical messages from the SCN that the light level is low. Melatonin influences the production of serotonin and this accumulates in the raphe nuclei in the hindbrain, near the pons, and stimulates the shutting down of the RAS (reticular activating system), which is closely linked with brain activity. So serotonin could be the switch to start sleep.

Jouvet (1967) has also identified noradrenaline as a biochemical affecting sleep. Noradrenaline accumulates in the locus coeruleus in the pons and if this area is damaged, noradrenaline levels fall and REM sleep is impaired. This led him to conclude that different areas of the brain and the corresponding neurotransmitters controlled the two types of sleep, NREM and REM. The raphe nuclei and its serotonin pathway controls NREM sleep; the locus coeruleus and noradrenaline pathway control REM sleep.

2 of 18

The nature of sleep continued...

A further factor is a biochemical, adenosine. This builds up during wakefulness and is then broken down during sleep. It has been suggested (NINDS, 2007) that the build-up causes drowsiness and could switch the brain into preparing for sleep mode.

An Ultradian Rhythm: The Stages and Cycles of Sleep

An ultradian rhythm repeats in a cycle of less than 24 hours. In sleep the cycles occur approximately every 90 minutes and the following stages occur within these cycles. Sleep is not a total loss of consciousness but there is a descent into reduced consciousness.

Most people have five cycles that last approximately 90 minutes. Deep sleep, or slow-wave sleep (SWS), occurs in only the first two cycles; REM sleep occurs in all of the cycles, and increases during the course of the night’s sleep.

NOTE: As we descend the sleep staircase into deep sleep, the brain (EEG) waves become larger and slower.

3 of 18

Outline Explanations of primary and secondary inso

Insomnia is the condition in which there are problems falling asleep and/or staying asleep, and the sleep that occurs tends not to be deep and is easily disturbed. Insomnia is also, unsurprisingly, linked with fatigue, having poor attention, impaired judgement, decreased performance, being irritable, and an increased risk of accidents. Insomnia can be categorized as primary or secondary insomnia depending on the cause.

Primary insomnia is the most common form of insomnia and has no clear underlying cause. There is a sleep problem, but there is no physiological or psychiatric cause, and it is likely that the sleep problem is the result of maladaptive behaviours or learning. The clinical characteristics are that the individual has suffered from insomnia for at least a month but this would not be linked with any other sleep disorder, such as parasomnia or narcolepsy, nor with another psychopathology such as clinical depression, nor with medications or substance abuse.

Secondary insomnia is insomnia that has a specific cause. Examples of such causes include sleep apnoea, restless legs syndrome, circadian rhythm disorders due to night shiftwork, and various medical, substance use, and emotional problems.

4 of 18

Factors Affecting Insomnia

These factors affect insomnia because they interfere with the natural progression of brain activity from daytime functioning to slowing down to sleeping. This progression was described earlier as part of the sleep–wake cycle.

Environmental Factors Stimuli such as bright lights, loud noises, very hot or very cold rooms, an uncomfortable bed, or a snoring companion can all contribute to insomnia because they interfere with the brain’s natural calming down of neural activity. A change in the location where one sleeps, can also boost brain activity and lead to insomnia, hence we often do not sleep well unless in our own bed!

Stress Acute stress, perhaps from a major life event such as an exam or a job change, can lead to insomnia, again because brain activity is heightened, the sympathetic ANS is active, and so the parasympathetic ANS cannot switch. Acute stress is transitory and so when it is over normal sleep should resume. However, with chronic stress the stressor persists, and so sympathetic ANS activity remains high, which can lead to long-term disrupted sleep.

5 of 18

More Factors Affecting Insomnia

Sleep Hygiene/Bedtime Behaviours Sleep hygiene refers to the habits and bedtime behaviour patterns that promote the calming and slowing down of the brain in preparation for sleep. Poor sleep hygiene refers to habits that do not promote this progression: consuming caffeine or alcohol or taking in nicotine interfere with brain activity and the sleep process.Poor sleep hygiene means the brain is very active, it is still alert and in daytime mode, and so the parasympathetic ANS (autonomic nervous system), the rest-and-digest mechanism, will not switch on and calm the brain, and insomnia is the result. Taking naps during the day is another aspect of sleep hygiene that can perpetuate insomnia.

Deadly Insomnia There are very rare cases in which insomnia becomes not just pathological but deadly. This has been identified as a genetic condition named as fatal familial insomnia (FFI). It seems to have started with a mutation affecting certain proteins in the brain, particularly in the thalamus, so that they mis-fold and form prions. These prions clump together, cause neuron deaths, and the area of the brain affected develops a sponge-like structure, full of holes. Death follows, usually within a year of the first signs of the disorder developing.

6 of 18

Describe explanations of other sleep disorders.(9)

Sleep walking Somnambulism (sleepwalking) is a relatively common sleep disorder, with estimates that it affects about one in ten of us at some point in our lives. Typically the eyes are open, though often described as glazed or staring in appearance. Somnambulism is most likely to occur during NREM stages 3 and 4, in slow-wave sleep. It can occur in REM sleep but this is much less likely. NREM sleep is earlier in the sleep period and so episodes of somnambulism tend to be in the earlier rather than later parts of the night. Somnambulism is most common in childhood, peaking just before or at the time of puberty, however it can continue into adulthood. An episode may last only a few seconds, but can last hours, and when awake the individual will have no memory of what they have been doing. The causes of somnambulism include a genetic predisposition, fatigue, previous lack of sleep, stress, or anxiety. In adults, alcohol and other drugs seem to act as triggers.

Narcolepsy Narcolepsy is rare but is characterised by chronic sleepiness, and so the individual may fall asleep at any time. Short naps of 10 to 20 minutes are common. Cataplexy can also occur.

7 of 18

This is when the muscles lose strength when strong emotions are experienced. The body may droop, sag, or even collapse as if paralysed, but there is no loss of consciousness, the individual does not faint. The episodes may be over within seconds or last some minutes. Sleep paralysis can also occur either at the beginning of sleep or when first awakening and is a brief loss of the ability to move, apart from the breathing muscles and eye muscles. This usually lasts a few minutes and can be very distressing, especially as it is sometimes accompanied by a sense of fear or dread, e.g. the individual thinking they are dead, and even hallucinations. Sleep hallucinations also may occur when dropping off to sleep or when awakening.

Research has established that in non-human animals, such as dogs and mice, a genetic mutation can cause narcolepsy. Mignot discovered that in dogs this mutation also produced a deficiency in a receptor for the neurotransmitter hypocretin, which blocks communication between neurones, particularly messages relating to when the body should wake. Injections of hypocretin in dogs reversed their narcolepsy, but this could not be generalised to humans as the human disorder has environmental as well as genetic causes, it is a nature and nurture phenomenom.

8 of 18

Describe two theories of formation, maintenance an

Reward/Need Satisfaction Theory

This theory is based on learning theory and states that we form relationships that provide rewards (reinforcement) and satisfy our needs. Rewards include companionship, being loved, sex, status, money, help, and agreement with our opinions, as shown by Foa and Foa (1975) Both operant and classical conditioning are influential.

  • Classical conditioning—Byrne (1971) pointed out that by classical conditioning we come to like people with whom we associate enjoyment and satisfaction even if they are not directly responsible for the positive experiences. When we experience enjoyable shared activities with people, they create in us a positive emotional feeling, known as a positive affect.

  • Operant conditioning—we like those who provide us with rewards and dislike those whose presence is unpleasant (i.e. punishing) because they are, for example, tedious, boring, or argumentative.

9 of 18

Evaluation of reward/satisfaction theory.

  • Accounts for research findings. The theory explains why factors such as proximity, similarity, and physical attractiveness are important factors in relationship formation and maintenance. They all provide easily obtainable, significant positive reinforcement with the minimum of effort.
  • It only accounts for the initial formation of relationships. The theory does not explain why relationships sometimes continue even when they become quite unsatisfactory.

  • Underestimation of altruism. The theory assumes that we are all motivated by a selfish desire to get as much as possible out of a relationship. It does not account for truly altruistic relationships such as regularly helping an elderly neighbour with no expectation of reward.

  • Individualistic bias. The theory is more relevant to Western individualistic cultures than to non-Western collectivist cultures. Lott (1994) speculates that they are also more relevant to men than to women.

  • Weakness of methodology. The research on which these theories are based depends heavily on “bogus stranger” studies, because the strangers the participants are being asked to rate are confederates of the experimenter. This is highly artificial and is unlikely to represent the way we meet people in real life and so the research lacks external validity as it may not generalise well to real-life relationships.

10 of 18

Economic Theories: Social Exchange Theory (SET)

The basic assumptions of social exchange theory (SET) are that relationships provide both rewards (e.g. affection, sex, emotional support) and costs (e.g. providing support, not always having your own way). Everyone tries to maximise rewards while minimising costs. Thibaut and Kelley (1959) argued that long-term friendships and relationships go through four stages: sampling, bargaining, negotiation, and institutionalisation, when rewards and costs are established and entrenched. How satisfied individuals are with the rewards and costs of a relationship will depend on what they have come to expect from previous relationships. In other words, they have a comparison level (CL) (Thibaut & Kelley, 1959), representing the outcomes they believe they deserve on the basis of past experiences—so if in the past they have had very poor relationships they may expect very little from subsequent ones. In addition, their level of satisfaction will depend on the rewards and costs that would be involved if they formed a relationship with someone else; this is known as the “comparison level for alternatives” (CLalt). All of this makes sense—if you are a very attractive and popular person, you can afford to be very choosy in your friendships and relationships.

11 of 18

Economic Theories - Equity Theory

Equity theory is an extension of social exchange theory. The basic assumption is that people only consider a relationship to be satisfactory if what they gain from it reflects what they give to it. This means that if one person contributes more, they feel they should get more out of it. Equity is especially important at the beginning of a relationship rather than when it is firmly established. Walster, Walster, and Berscheid (1978) expressed key assumptions of equity theory, such as: individuals try to maximise the rewards they receive and minimise the costs; there is negotiation to produce fairness; distress and relationship breakdown may follow when the relationship is unfair or inequitable.

Evaluation Explanation of individual differences. Levinger’s theory takes account of at least some of the complex reasons why people either remain in marriages or leave them. By doing this, it explains why there is not a strong relationship between levels of satisfaction and likelihood of leaving the marriage. People in very unsatisfactory marriages often do not dissolve them, yet those in mediocre marriages sometimes do. If the barriers to leaving are high and the alternatives not very attractive, then people tend to stay

12 of 18


  • Underestimation of altruism. SET assumes that people are self-centred whereas many relationships are not based on this principle (see Evaluation of reinforcement and need satisfaction theories, in the previous section).
  • Cross-cultural criticism. These principles apply more to individualistic than to collectivist cultures, due to the focus on individual gain.

  • Explains influences on relationships. The equity theory takes account of rewards and costs and thereby explains the matching hypothesis, i.e. it explains why people are usually equally physically attractive as well as equal in other ways, but also why, for example, a rich, unattractive man can attract a younger, far more attractive woman.
  • Does not account for change over time. Because equity is more important at the beginning of a relationship and people are quite tolerant of some inequity once the relationship is well established, it has limited value in explaining the maintenance and dissolution of relationships.
  • Not all marriages are based on equity. Clark and Mills (1979) contend that most marriages are not based on exchange principles. They believe that in many marriages people gain satisfaction by responding to each other’s needs.

13 of 18

Psychological Explanations of Gender Development

Explain what is meant by gender dysphoria. (5)

Gender dysphoria (also known as gender identity disorder) is a condition in which people are uncomfortable with the gender to which they have been assigned (dysphoria means unhappiness). In the extreme, this can lead to transsexualism, a desire to change your gender. Most people are happy with the gender in which they have been reared but in a few cases individuals do not feel that they have been assigned the correct gender. Some girls feel as if they should be a boy and conversely, some boys feel that they are a girl. This is more common in boys but occurs in both sexes.

Outline one or more explanations of gender dysphoria. (9)

1. The biological explanation: the influence of prenatal hormones. Girls have sex chromosomes known as ** whilst boys have sex chromosomes known as XY. One explanation of gender dysphoria is that it is caused by unusual development in parts of the brain before birth. There are small areas of the brain that are different in males and females. The theory is that in people experiencing gender dysphoria one of these areas has developed in a way that corresponds to the opposite sex of their other biological sex characteristics. It is possible that hormones can cause parts of the brain to develop in a way that is not consistent with the genitalia and, usually, with the chromosomes. This means that the brain has not developed in a way that corresponds to the gender assigned to the child at birth.

14 of 18

Reasearch Evidence Kruijiver et al. (2000, see A2 Level Psychology page 241) point out that males have around twice as many somatostatin neurons than do women. They found that in both male-to-female transsexuals and female-to-male transsexuals, the number of these neurons corresponded to their gender of choice, not to their biological sex. They concluded that this clearly points to a neurobiological basis of gender dysphoria.


Support from research. The research evidence cited above supports the biological explanation for gender dysphoria. Some research contradicts the theory. Rekers et al. (1979, see A2 Level Psychology page 241) examined 70 “gender disturbed” boys and found no evidence for prenatal hormone treatment of the mothers nor any history of hormonal imbalance in them. Alternative theory. The biological theory underestimates the role of social factors such as the family. The next theory offers an alternative view on the cause of gender dysphoria.

15 of 18

Biological Influences on Gender

Outline the role of hormones and genes in gender development. (10)

Prenatal Sexual Development

When the ovum (egg) combines with a sperm, the zygote that is formed will either have ** chromosomes, and be a girl, or XY chromosomes, and be a boy. The sequence of sex development is as follows:

  • For 7 weeks development is virtually identical for girls and boys.

  • The Y chromosome then induces the release of testosterone, which stimulates the growth of male sex organs. If no testosterone is released, the foetus develops female reproductive organs.

  • In a rare condition, known as complete androgen insensitivity syndrome, genetic males (i.e. those with XY chromosomes) are insensitive to the male hormones and do not develop male genitalia. They are born looking like girls and are often brought up as girls because the condition is not usually detected until puberty.

16 of 18

The Influence of the Sex Chromosomes

We have discussed one influence of the Y chromosome: to induce the release of testosterone in the developing foetus.

The Y chromosome is one fifth of its size, hence boys carry less genetic material than girls, and this may be one reason why males are more vulnerable than females throughout their lives. Montagu (1968, see A2 Level Psychology page 245) listed 62 specific disorders that are largely or wholly due to sex-linked genes and found mostly in males, including some very serious ones, such as haemophilia, as well as less important ones such as red/green colour-blindness.

17 of 18

The Role of Hormones Each sex has identical sex hormones; the difference between them is the amount they produce. Within normal biological development, females produce a preponderance of female sex hormones (oestrogen and progesterone), whilst males produce a preponderance of androgens (a collection of male hormones) of which one of the most important is testosterone.
Up to about the age of 8–10, negligible amounts of sex hormones are produced by either sex but after that both sexes produce more male
and female hormones. From around 11 years of age, both girls and boys increase their production of female hormones but females produce far more than boys. Conversely, once children reach puberty both sexes increases their production of male sex hormones rapidly but boys more so than girls.

RESEARCH EVIDENCE Young, Goy, and Phoenix (1964) demonstrated that pregnant monkeys injected with androgens have given birth to females with masculinised genitalia and who act in masculine ways, such as being threatening and aggressive, engaging in rough-and-tumble play, and mounting females.
18 of 18


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »