First Glance
| Fundamentals |
General Perspectives of Sleep |
|
Introduction A healthy body and a healthy mind is the prime necessity for all human beings. To achieve good health, a number of approaches have been tried which include medicines, nutrients, naturotherapies etc. However, in this run for health, man has forgotten the one most basic remedy for all illness SLEEP. Sleep is a human need as basic as air, food and water. One third of the average person’s life is spent in sleeping. Sleep is essential for emotional and physical well being. With sleep a number of physiological changes occur affecting the respiratory functions, cardiac functions, muscle tone and hormone secretion. Sleep basically is a restorative process in which the body and the mind repair themselves . Sleep also helps in regulating the temperature and helps in energy conservation. Knowledge of sleep pattern and architecture is an important part of clinical practice, as an disturbed or interrupted sleep leads to daytime mental and physical impairments. In addition, sleep disturbance may be an early sign of an underlying medical disorder. Insomnia is the commonest sleep disorder involving a disruption of the normal sleep architecture. Insomnia is not a disease but a very common, usually temporary, sense of not having had enough sleep to feel refreshed, it may be experienced as an inability to sleep despite being tired, or as a fitful sleep that leaves one fatigued upon awakening. Insomnia is treated with sedative-hypnotics. Thus sleep is a regular, recurrent, easily reversible state that is characterized by calmness, peacefulness and decreased response to external stimuli, and from which a person can be easily woken up. Control of Sleep The ability of a person to stay awake is controlled by the Reticular activating system (RAS) present in the thalamus and cerebral cortex. Inhibition of this system results in sleep. Sleep - Wake Cycle Sleep-Wake cycles are governed by the circadian rhythms, which usually run on a 24-hour cycles with two natural daily peak times for sleeping, at night and at mid-day. Sleep Production As light fades, the cells in retina of the eye pass a message directly to a cluster of nerve cells called suprachiasmatic nucleus (SNA) which is located in the hypothalamus. The SNA then signals the pineal gland to produce the hormone melatonin, which is the brain’s messenger for changes in light. It causes a drop in temperature and sleepiness. The neurotransmitters histamine, norepinephrine and serotonin are involved in wakefulness. Physiology of Sleep and Wakefulness Most adults sleep 6 to 10 hours per night, with an average of 8 hours. A sleep of less than 4 hours or more than 10 hours is associated with high mortality although the timing, duration, and internal structure of sleep vary among apparently healthy individuals and also as a function of age. At the extremes, infants and elderly have frequent interruption of sleep. Sleep latency is the time required to fall asleep. Average sleep latency is 15 to 20 minutes. Insomnia patients have a longer sleep latency. States and Stages of Sleep States and stages of human sleep are defined on the basis of characteristic patterns in the electroencephalogram. The continuous recording of this array of electrophysiologic parameters to define sleep and wakefulness is termed polysomnography. Polysomnographic
|
