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Time: 12 hours
Level: Intermediate
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 Introduction Resource- This unit examines issue of nature and nurture, how genes and the environment interact in the development of the nervous system to make each of us unique. In particular it looks at the period from conception...
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- 1.1 Introduction Resource
- This unit addresses the question of how the differences between individuals, especially in behaviour, arise during development. Development, the transformation of the single cell, the zygote, into an adult...
- 1.2 The ‘genes and behaviour’ problem Resource
- Amidst the progressive change to the brain and nervous system that occurs during development, there is one constant, one fixed element; the set of deoxyribonucleic acid, DNA, molecules found in each cell....
| | | | | 2 Growth and development: the big picture
- 2 Growth and development: the big picture Resource
- The scale of the problem facing the human zygote is vast. The zygote, the single cell resulting from the fusion of a sperm and an ovum, is about the size of a full stop on a nomal printed page, yet within...
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- 3.1 Introduction Resource
- We each begin life with a unique genome. As we grow and develop, we are each subjected to a range of factors that influence the way development proceeds. Most of those factors are common to us all, the...
- 3.2 Small babies Resource
- Development continues in the womb until birth, which, in humans, is about 38 weeks after conception. (The often quoted duration of pregnancy of 40 weeks is based on pregnancy beginning on the first day...
- 3.3 Plasticity and permanency Resource
- The visual system relies on, amongst other things, the exquisitely precise connections between the retina, the lateral geniculate nucleus of the thalamus and the visual cortex. In precocial organisms,...
- 3.4 Sensitive periods Resource
- The steroid hormone testosterone plays a major role in the development of mammals. In particular it is instrumental in causing differences between males and females. One well explored difference concerns...
- 3.5 Summary of Section 3 Resource
- The developing organism is nudged onto different developmental paths by the environment in which it finds itself. Thus the experience of being premature, or of experiencing only horizontal visual stimuli,...
| | | | | 4 Confounded variables: sensitive skin
- 4.1 Parental behaviour Resource
- A moment's reflection will convince you that parental behaviour differs from one family to another. The effect that different parental styles have on the development of the recipient offspring is very...
- 4.2 Licking/grooming-arched back nursing Resource
- Rat mothers perform a number behaviours towards their pups: they build a nest for their pups, keep them in it and occasionally lick them and nurse them. (Rat fathers have a parental role too but it is...
- 4.3 Small babies: the sequel Resource
- Evidence that some of the consequences of being born prematurely were enduring was discussed in Section 3.2. However, what emerges from Section 4.2 is that the quality of maternal care can alter the course...
- 4.4 Summary of Section 4 Resource
- Two important points emerge from this section. The first is the powerful effect of maternal contact on the development and later behaviour of their charges. In the Feldman study the disadvantages of prematurity...
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- 5.1 The nervous system Resource
- Development has so far mostly been assessed in terms of the gross performance, the overt behaviour, of the organism. Relationships have been established between certain environmental events and certain...
- 5.2 Sexually dimorphic nucleus of the preoptic area (SDN-POA) Resource
- As well as affecting behaviour (Section 3.4) neonatal testosterone also affects the physical characteristics of some areas of the brain. One of these is a small area of the hypothalamus, the medial preoptic...
- 5.3 Transcription factors Resource
- At various places in this unit, reference is made to new proteins being made, or to genes being switched on. The control of gene transcription is a hugely complex area and well beyond the scope of this...
- 5.4 Retinoic acid Resource
- The retinoic acid story is both distressing and illuminating. It is distressing because with hindsight it is possible to see how the suffering of many people could have been averted. It is illuminating...
- 5.5 Summary of Section 5 Resource
- When oestradiol combines with its receptor inside neurons, the cell produces proteins which protect it from cell death. As a consequence, the male brain, which has oestradiol in its neurons in early life,...
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- 6.1 The intricacies of neuron growth Resource
- Particular nerves, such as those sensory nerves that arise from the nasal retina (the side of the retina adjacent to the nose), cross the midline; other sensory nerves, such as those that arise from the...
- 6.2 The growing axon: growth cones Resource
- The growth cone is a small area of active tissue at the tip of a growing axon (Figure 15). As the growth cone moves forward, it adds new material to the cell membrane and so extends the axon. (New axonal...
- 6.3 Directing the growth cone Resource
- The growth of the growth cone has been likened to the progress of a climber. The climber can only go where there are satisfactory hand and foot-holds and where progress is not blocked by physical obstacles...
- 6.4 Crossing the midline: a case study Resource
- Many neurons on the left side of the body make contact with targets on the right, contralateral, side of the body, and vice verse. Crossing the midline is particularly prevalent in descending neurons (e.g....
- 6.5 Summary of Section 6 Resource
- Growth cones respond to proximal and distal cues. The proximal cues in the extracellular matrix or other cells affect adhesion and result in chemotactic guidance. Distal cues are also in the extracellular...
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- 7.1 Neuron proliferation Resource
- There is a huge proliferation of neurons in early life. Even whilst that proliferation continues, some cells, e.g. neuroblasts, stop being able to divide. At some later stage the proliferation itself virtually...
- 7.2 Selected to survive: studies of the PNS Resource
- Viktor Hamburger carried out a series of classic embryologieal experiments over a period of about 30 years. He investigated the relationship between the size of target tissue in chick embryos and the size...
- 7.3 Selected to die: studies of the CNS Resource
- Recent evidence has revealed that during development in mice, cell death occurs in two phases. The first phase is at about E15–E17 days, during neuron proliferation, and will not be considered further...
- 7.4 Elixirs of the nervous system: neurotrophins Resource
- According to Section 7.2 axons obtain an elixir from targets at their synapses.
- 7.5 What do neurotrophins do? Resource
- Neurotrophins shut down the mechanism of apoptosis. Neurotrophins do this by attaching to receptors in the cell membrane of the innervating axon and activating a cascade of biochemical reactions. The sequence...
- 7.6 Synaptogenesis Resource
- The formation of synaptic connections is an essential property of nervous system development. Synapses are formed between neurons and also with targets that are not part of the nervous system, e.g. muscle....
- 7.7 Neurogenesis Resource
- Brains contain within them the seeds of their own salvation and the seeds of their own destruction. In its early stages, the brain produces vast numbers of neuroblasts as stem cells divide at a huge rate,...
- 7.8 Summary of Section 7 Resource
- This section has sought to illustrate the formation of connections between neurons and their targets by exploring a few examples. The picture that emerges is one of cells at different stages of development...
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- 8.1 Genes and behaviour Resource
- In the preceding sections many different proteins have been mentioned. These proteins are the receptors, signals, channels, enzymes, transporters, structural components and transcription factors that enable...
- 8.2 Wilson's disease Resource
- The effects of a protein that is absent, or present but not doing its job, may not be evident for many years. This is called late onset, and is exemplified by Wilson's disease. Many molecules within the...
- 8.3 Lissencephaly Resource
- Lissencephaly, literally meaning ‘smooth brain’, is characterised by the absence of sulci and gyri, and by a four-layered cortex, instead of the usual six layers, with the majority of cortical neurons...
- 8.4 Fragile X syndrome Resource
- Fragile X syndrome is the final example of a genetic disease considered here.
- 8.5 Summary of Section 8 Resource
- Genes do influence development. However, genes do not always determine the developmental path. The prognosis for Wilson's disease is very good, because environmental intervention is possible. The prognosis...
| | | | | 9 Genes and their influence on behaviour revisited
- 9.1 The psychological arena Resource
- The examples in the previous section followed the traditional medical approach, namely that there is a disease, it can be diagnosed (identified), and the cause of the disease, be it viruses, bacteria,...
- 9.2 Antisocial behaviour disease Resource
- The psychological arena is hugely complex because there are additional issues of responsibility and treatment. Briefly, society takes a more lenient attitude towards the behaviour of someone who is ill...
- 9.3 Monoamine oxidase A, maltreatment during childhood and later violence Resource
- One Dutch family was found to have a history of antisocial (aggressive) behaviour. Genetic studies were conducted and a potential culprit gene MAOA, monoamine oxidase A, identified. The aggressive individuals...
- 9.4 Summary of Section 9 Resource
- This section has illustrated what has to be done, by way of a long-term study, to yield meaningful information on the relationship between genes and development and the behaviour of the organism. It also...
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- 10 Unit summary Resource
- The unit began by considering what factors contribute to individual differences. The case was made, with the spiders, and later with genetic diseases, that the genome was very important. Subsequent sections...
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- End of unit questions Resource
- Explain your reasons for agreeing or disagreeing with each of the following sentences.
| | | | | References and Acknowledgements | | |
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