3.5.3 Mechano-electrical transduction is rapid Many other sensory receptors, such as photoreceptors and olfactory neurons, employ second messengers in the transduction process. This is not true for hair cells. The rapidity with which they respond makes this impossible. In order to deal with the frequencies of biologically relevant stimuli, transduction must be rapid. The highest frequency humans can hear is about 20Â 000 Hz. This in effect means that hair cells must be able to turn current on and off 20Â 000 times per second (200Â 000 tim
3.5 Neural transduction The critical event for the transduction of sound into a neural signal is the bending of the stereocilia of the hair cells. In this section we will examine how the flexing of the basilar membrane leads to the bending of the stereocilia and the production of a neural signal.
Richard Feynman Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: Introduction This unit is an adapted extract from the course Science in context
(S250) In recent years, scientists have made huge gains in their understanding of how genes can be altered and transferred from one organism to another – but that knowledge has been acquired amidst controversy and concern. The deep ethical concerns that have resulted from the emergence of genetic manipulation are explor 2.2 Interstellar space is not empty The difference between the apparent brightness of a star (as measured by its apparent magnitude), and its luminosity (represented by its absolute magnitude) is defined by the distance of the star. We can explicitly state this relationship as in Equations B and C: 2.1 Introduction In all the analysis of stellar properties discussed so far we have made an implicit assumption – that light emitted by a star is not changed between its emission and its arrival outside the Earth's atmosphere, except by the inverse square law (i.e. it is reduced by a factor of d2, where d is the distance to the star) and by the Doppler effect. However, this may not be the case. References 4.1 Scientific approaches Even after many years of research, the phenomenon of hibernation continues to be a mystery to scientists. Despite coming nearer to an understanding of how and why it happens, some fundamental questions remain unanswered. Is there a genetic basis underlying the evolutionary predisposition of animals to hibernate, given its occurrence in many groups of vertebrates and invertebrates? Is the problem of metabolic adaptation in cells separate from thermal regulation which occurs throughout the orga 5.2 Sexually dimorphic nucleus of the preoptic area (SDN-POA) 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 area, which, although small, is much larger in males than in females. This size difference is mediated by testosterone. 4.4 Summary of Section 4 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 were essentially overcome by early maternal contact. The second point is that some behavioural traits really do run in families, without being genetic. The Francis study clearly showed that some aspects of Open Field behaviour were the result of nursing care. 4.1 Introduction to minerals and why we need them Both vitamins and minerals are essential in the diet in small quantities and so they are often grouped together as micronutrients. Which items in the diet are classified as macronutrients? Introduction Genes are units of inheritance that contribute to a person’s behaviour and health. In this unit you will learn what genes, DNA and chromosomes are and how they combine to make the human genome. You will also learn how the principles of inheritance work, the effect that our genetic make-up has on health, and how genetic material is passed on from generation to generation. This unit is an adapted extract from the course Author(s): Learning outcomes After studying this unit you should understand: how the linear sequence of DNA within a gene is related to the linear sequence of amino acids of a protein how the information in DNA is carried via RNA to make a protein how RNA is synthesised from DNA by the process of transcription where the processes of transcription and translation occur within the cell Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: Learning outcomes After studying this unit you should understand: something of the role of a genetic counsellor and its non-directiveness the difference between pre-natal diagnosis, childhood testing and adult testing and give some examples of diseases that may be tested for the ethical and moral difficulties involved in making decisions on whether or not to carry out such tests Introduction This unit looks at three different uses of genetic testing: pre-natal diagnosis, childhood testing and adult testing. Such tests provide genetic information in the form of a predictive diagnosis, and as such are described as predictive tests. Pre-natal diagnosis uses techniques such as amniocentesis to test fetuses in the womb. For example, it is commonly offered to women over 35 to test for Down's syndrome. Childhood testing involves testing children for genetic diseases that may not 1.7.1 Research methods in context Any established discipline has a tradition of practice. Many disciplines have established methodologies which prescribe the selection, combination and sequencing of the methods and techniques to be employed. Others select methods and techniques less prescriptively and borrow more broadly across domain boundaries. All disciplines require an appropriate application of methods, in order to ensure rigour. Hence, one key skill is the demonstration of an appropriate knowledge and competence 1.2 Different reasons for doing PhDs Just as there are different views of what a PhD is or means, there are different reasons for undertaking a PhD, ranging from the pragmatic – acquiring a research credential for academia or for industry – to the idealistic – aspiring to deep scholarship. And students have many reasons in between, including things like curiosity, a drive to chase a long-held question, and the need to prove oneself. What's important here is not the reason for starting, but the compelling reason for finishi 1.1 Thoughts on a PhD Entering students often think of a PhD as a ‘magnum opus’, a brilliant research project culminating in a great work. This is rather a demanding model, and few students win Nobel Prizes as a result of their doctoral studies. More realistically, a PhD is research training leading to a research qualification. The PhD is a passport to a research career. There are other views of a PhD, as well. Getting a PhD can be a ‘rite of passage’, prerequisite to admission into the academic ‘t
Richard P. Feynman (1918–1988)
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Activity 24
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