Sleep is the fundamental anabolic process common to all life forms, plant and animal. In animals, the sleeping state is characterized by an absolute minimal degree of consciousness and decreased responsiveness to the surrounding world.
Sleep is a dynamic, constructive time of healing and growth for animal organisms. The simple substances which have been ingested during the catabolic (awake) period are synthesized into the complex proteins of living tissue. The waking life of animal organisms is a dynamic, destructive time because the organisms' complex proteins are torn down and exhausted as they are used for activities including locating and ingesting preformed organic molecules to meet the immediate energy needs of the wakened state and to provide the building block proteins which fuel the anabolic dynamics that occur during sleep.
It may well be that plant organisms exist in a perpetual anabolic (sleep) state. No catabolic (wakened) state has ever been documented for any plant organism and, by definition, plants do not exhibit the characteristics of animal organisms in a wakened state.
Every animal organism's lifelong alternation between anabolic and catabolic periods, what we view as being asleep and being awake, is a cyclical pattern which occurs daily. The human inner body clock seems to be based on a 24.5-25.5 hour cycle, according to some studies.
The daily cycle of sleep and wakefulness is regulated by various hormones produced by the hypothalamus and external stimuli, the level of sunlight being the most obvious example. The body's levels of certain neurohormones are highly correlated with the sleep and wakened states. The levels of the orexin (hypocretin) neurohormone pair rise sharply to mark the transition from the anabolic, sleep state to the catabolic, wakened state. The melatonin level is high at times during the anabolic state........
