By Homar N. Murillo
Sleep is one of the most investigated subjects in neuroscience and psychology but it is also the least understood in terms of mechanism and functions. However, it is clear that sleep is an important biological need of complex organisms. There seems to be a correlation between brain complexity and the hours needed for sleep.
Among vertebrates, mammals have the longest hours of sleep. The number of hours tends to drop as the organism becomes much simpler. For instance, most fish species hardly need to sleep. They only need to sleep one hemisphere of their brain at a time. This is especially true for sharks which do not have swim bladders. Hence, they need to swim all the time in order to avoid sinking at the bottom of the sea.
On the other hand, humans have complex brains that require an average of eight hours of full sleep. This means that both hemispheres of the brain must be rested and temporarily isolated from environmental stimuli. However, mere rest and isolation from stimuli are insufficient. A complete sleep must also have dream component. A dreamless sleep or a coma-like sleep does not have the same rejuvenating effect as a sleep with dream component. Dreaming occurs during the rapid eye movement (REM) cycle.
Patients who suffer from insomnia and induced sleep deprivation typically experience a wide range of psychological and physiological problems. These include hallucinations, irritability, hypertension, loss of focus, heart disease and weakened immune system. Prolonged sleep deprivation such as in the case of chronic insomnia can lead to death. Sleeping pills do not help in the long run. They may actually worsen the situation.
Complete sleep apparently has the function of allowing the brain synapses to organize and consolidate memories and new learning. It also helps in removing garbage information, thereby preventing information overload. People who are deprived of sleep have slower learning ability. They also tend to be less socially adaptable.
Based on research, sleep also has crucial role in maintaining hormonal balance, regulating temperature and maintaining normal heart rate. People who do not have sufficient sleep have the tendency to have abnormal metabolic functions because of hormonal imbalance.
Some of the hormones that are closely associated with the sleep-wake cycle are melatonin, cortisol, and thyroid stimulating hormone (TSH). Melatonin directly regulates sleep. Cortisol is a stress hormone which is primarily responsible for increasing blood sugar level. It also aid in metabolizing fat, protein and carbohydrate. TSH is responsible for stimulating the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which is crucial in metabolic processes in almost every tissue in the body. Sleep also has direct role in normal growth. The normal production of prolactin and growth hormone is critically determined by normal sleep.
Sleep is one of the most investigated subjects in neuroscience and psychology but it is also the least understood in terms of mechanism and functions. However, it is clear that sleep is an important biological need of complex organisms. There seems to be a correlation between brain complexity and the hours needed for sleep.
Among vertebrates, mammals have the longest hours of sleep. The number of hours tends to drop as the organism becomes much simpler. For instance, most fish species hardly need to sleep. They only need to sleep one hemisphere of their brain at a time. This is especially true for sharks which do not have swim bladders. Hence, they need to swim all the time in order to avoid sinking at the bottom of the sea.
On the other hand, humans have complex brains that require an average of eight hours of full sleep. This means that both hemispheres of the brain must be rested and temporarily isolated from environmental stimuli. However, mere rest and isolation from stimuli are insufficient. A complete sleep must also have dream component. A dreamless sleep or a coma-like sleep does not have the same rejuvenating effect as a sleep with dream component. Dreaming occurs during the rapid eye movement (REM) cycle.
Patients who suffer from insomnia and induced sleep deprivation typically experience a wide range of psychological and physiological problems. These include hallucinations, irritability, hypertension, loss of focus, heart disease and weakened immune system. Prolonged sleep deprivation such as in the case of chronic insomnia can lead to death. Sleeping pills do not help in the long run. They may actually worsen the situation.
Complete sleep apparently has the function of allowing the brain synapses to organize and consolidate memories and new learning. It also helps in removing garbage information, thereby preventing information overload. People who are deprived of sleep have slower learning ability. They also tend to be less socially adaptable.
Based on research, sleep also has crucial role in maintaining hormonal balance, regulating temperature and maintaining normal heart rate. People who do not have sufficient sleep have the tendency to have abnormal metabolic functions because of hormonal imbalance.
Some of the hormones that are closely associated with the sleep-wake cycle are melatonin, cortisol, and thyroid stimulating hormone (TSH). Melatonin directly regulates sleep. Cortisol is a stress hormone which is primarily responsible for increasing blood sugar level. It also aid in metabolizing fat, protein and carbohydrate. TSH is responsible for stimulating the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which is crucial in metabolic processes in almost every tissue in the body. Sleep also has direct role in normal growth. The normal production of prolactin and growth hormone is critically determined by normal sleep.
