Description: Segment 1 Gilliland introduces Nunn and Halsey. Nunn speaks to camera. He describes how this is the first of a pair of lectures on the subject of inhalational anaesthetic agents. In this part the theories of the molecular basis of anaesthetics will be covered. Nunn usefully defines inhaled anaesthetics as part of a group of inhaled substances which produce reversible loss of consciousness. He shows a table listing the main inhalational anaesthetic agents currently in use. He briefly describes the action and effective dose level of each one. Time start: 00:00:00:00 Time end: 00:05:21:12 Length: 00:05:21:12 Segment 2 Nunn discusses the lowest level of anaesthetic needed to suppress a reflex response to a surgeon's blade - this is known as the 'minimum alveolar contraction', or MAC. He then talks about the anaesthetic, Xenon, pointing out that, like many other inhalational anaesthetics, does not change in composition whilst in the body - it is exhaled in exactly the same composition as it was when originally inhaled. Nunn makes a distinction between light anaesthesia in which reflex reactions still exist and deep anaesthesia in which there are no reflex reactions present. Time start: 00:05:21:12 Time end: 00:09:45:05 Length: 00:04:23:18 Segment 3 Nunn talks about the site of action in the body at which anaesthetics produce narcosis. He assumes it is the brain but cannot say which part of the brain is affected by anaesthesia - current thought is that it is not an overall suppression of the brain so much as a specific area that responds to anaesthesia. He introduces, instead, what is known about the molecular site of anaesthetic action and passes over to Halsey to continue. Halsey reinforces the important point that anaesthesia produces a reversible state of unconsciousness. Therefore any actions it has on molecules must be of a weak nature - he describes them as 'intermolecular forces' rather than 'chemical bonds.' He narrates over a cascading list showing different types of energy in various intermolecular bonds he briefly describes each one. Time start: 00:09:45:05 Time end: 00:15:02:15 Length: 00:05:15:10 Segment 4 Halsey gives a brief history of the area of chemical bonding, in particular mentioning the work of Linus Pauling. He demonstrates, using some 3-dimensional models, how interactions between molecules can occur. He describes in some detail a variety of different molecular interactions and shows a slide of one of these, the Davson-Danielli membrane. Time start: 00:15:02:15 Time end: 00:20:38:17 Length: 00:05:36:02 Segment 6 Halsey hands back to Nunn. Nunn moves on to discuss the side effects of anaesthetics. He believes that the study of the side effects is a very useful way of understanding how anaesthetics work. In the most technically heavy part of the lecture, he describes the side effects of a number of different anaesthetic agents and uses graphs to plot their effects against one another. Time start: 00:25:45:00 Time end: 00:30:49:13 Length: 00:05:04:13. Segment 7 Nunn admits that there can be an infinite amount of differences in the actions of anaesthetics on various target molecules. He says it is a 'fact of life' that no two anaesthetics will have the same side effects. He hands over to Halsey to conclude the lecture. Halsey states that it is the ultimate aim of anybody researching the mechanisms of anaesthesia to determine how these chemically inert substances can produce a reversible depression of the central nervous system. He then sums up, briefly, where current research is at. Firstly there are experiments on animals and humans, then there are neuropharmacological experiments and experiments on various model systems. Finally, he says, there are studies on biological systems at a cellular level - this is to be the topic of the second lecture in the series. Time start: 00:30:49:13 Time end: 00:37:44:13 Length: 00:06:55:00