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Fibres leave the SCN to reach the ventrolateral preoptic area (VLPO) of the anterior hypothalamus multisynaptically. They initially relay in the sub-paraventricular zone before synapsing predominantly in the dorsomedial nucleus of…

The clock in the SCN, through its neurological connections, has a circadian influence not only on sleep, but also on temperature control, hormone secretion and other functions. The multisynaptic processing of the SCN…

Circadian rhythm periodicity
Circadian rhythms have a periodicity of around a day, which is longer than ultradian rhythms of,  for instance, REM sleep and shorter than infradian rhythms such as the menstrual cycle. The…

Impulses reach the SCN from retinal receptors which lie particularly in the lower and nasal quadrant of the retina. The receptors are the retinal ganglion cells and their light-sensitive pigment is…

The characteristics of this rhythm generator are largely genetically determined. At least 12 genes have been identified on chromosome 5 which, through inhibiting or promoting protein transcription, form a complex negative…

REM sleep is almost never normally entered from wakefulness except in infants. It is preceded by NREM sleep, usually stages 1 and 2. It can therefore be regarded as a type of arousal…

This includes a variety of mechanisms that influence sleep but which are independent of the time spent awake and of circadian and ultradian rhythms. They modify the sleep–wake cycle according to changes in the environment…

Even before the onset of NREM sleep the heart rate falls in parallel with the reduction in body temperature and is related to the fall in metabolic rate. Vasodilatation…

Homeostatic control of cardiovascular function in response to, for instance, changes in blood volume or temperature is poor in REM sleep. There is considerable variability of heart rate and…

Less saliva is produced during sleep than during wakefulness, possibly partly related to a reduction in oromotor activity, but the volume is similar in NREM and REM sleep. The…

The minute ventilation falls (1.23) and the arterial P_co2  rises by 2–3mmHg. The stage of NREM sleep oscillates frequently at sleep onset and the threshold for carbon dioxide to…

There are several aspects of the costs of sleep disorders to society.

1 Development of other diseases which could have been avoided if the sleep disorder had been recognized and treated earlier. An…

Sleep occupies approximately 8h of each 24-h cycle, but much less attention has been paid to the medical problems during this phase of life than to those that occur during wakefulness.

There are…

It is common for there to be a prolonged episode of wakefulness before take-off on space travel. There may be as long as 30h of continuous wakefulness before sleep is first obtained during…

Disrupted sleep at night is often the cause of elderly people requiring long-term residential and nursing home care, but the environment that these institutions provide frequently exacerbates the sleep disruption.

Lack…

Most people fall asleep more readily and sleep more soundly in familiar surroundings, except those with psychophysiological insomnia. This is exemplified by the ‘first night’ effect in the sleep laboratory, which is characterized by…

Behavioural treatments
These include cognitive behavioural therapy which aims to alter attitudes about comfort eating, and anxiety about lack of food availability and the moral duty to finish…

Obesity is related to the following sleep conditions.

Sleep deprivation and fragmentation
Sleep deprivation and fragmentation lead to insulin resistance and other hormonal and autonomic changes with the result that appetite is…

Sleep disorders may affect the bed partner, family, friends, carers and even neighbours in addition to the patient. The partner may become concerned because of the implications of the sleep disorder, especially when…

The control of sleep is closely linked to feeding behaviour and energy expenditure. These determine the body weight and in particular the body fat and lean body mass. Body weight and body mass index…