- Created by: ainemurphy
- Created on: 18-01-10 10:31
Biological Rhythm: Infradian Rhythm.
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 (ovarian hormones), 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.
Sleep: Describe The Nature of Sleep.
The sleep–wake cycle, as covered in the previous section, 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.
However, the circuitry involved is more complex than Jouvet suggests as the pons, raphe nuclei, and locus coeruleus (among others) are involved in sleep, along with a number of different neurotransmitters, especially serotonin, noradrenaline, and acetylcholine. Supporting evidence comes from links to other brain areas, and also shows that the relationships between brain areas and sleep may not be clear-cut as damage to the locus coeruleus or its pathways does not affect REM sleep.
A further factor is a biochemical, adenosine. This builds up during wakefulness and is then broken down during sleep. It has been suggested that the build-up causes drowsiness and could switch the brain into preparing for sleep mode.
Please refer back to the stages and cycles of sleep as an ultradian rhythm, as covered in the previous section, as this is also important to our understanding of the nature of sleep.
Disorders of Sleep: Primary and Secondary Insombia
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 is not a single condition as there are different forms based on the degrees of severity (mild, moderate, severe, acute, chronic) and the causes of the insomnia.
Insomnia can be categorised 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. Worrying about the insomnia can lead to a cycle that is hard to break because the more a person focuses on their sleep problems the less likely they are to get good quality sleep.
Disorders of Sleep: Explainations of Other Sleep D
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.
The genetic element in somnambulism is supported by Hublin et al. (1997) who used the Finnish twin cohort and found that the genetic contribution to somnambulism in childhood was 66% in men and 57% in women, and for adult somnambulism was 80% in men and 36% in women. The sex difference in childhood somnambulism does not seem significant, but it is puzzling why there is such a major difference between the sexes in adult somnambulism. Szelenberger, Niemcewicz, and Dabrowska (2005) offer an explanation of sleepwalking as they found both low and declining levels of delta waves that could be signs of a chronic inability to sustain slow-wave sleep. The main issue with somnambulism, apart from the anxieties it may cause, is the moderately high risk of somnambulists injuring themselves during an episode—in some cases bones have been broken!
Relationships:Two theories of formation, maintenan
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.
" " "
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 (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” . 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.
Gender: What is Meant By Gender Dysphoria.
Gender dysphoria is a condition in which people are uncomfortable with the gender to which they have been assigned. 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.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.
" " " " "
2. Family constellations. Stoller (1968) points out that certain family conditions are associated with gender dysphoria. For boys who want to be girls, he suggests that there is an over-close relationship with the mother and a distant father. For girls who want to be boys, he suggests that that they have a depressed mother in the first few months of their life and a father who is either not present or does not support the mother but leaves the child to try to control the mother’s depression.
Rekers links gender dysphoria in boys to absence of a father figure, either physically or psychologically.
Bleiberg, Jackson, and Ross (1986) have linked the development of gender dysphoria with an inability to mourn a parent or an important attachment figure in early life.
De Ceglie (2000) suggests that parents have a strong desire for a child of the opposite sex and, not necessarily deliberately, reinforce gender-inappropriate behaviour.
Biological Influences on Gender: Role of Hormones
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.
" " " " " " "
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.
" " " " " " "
The Role of Hormones
The role of hormones in sexual development is of enormous importance.
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.