Abstract
The knowledge of sleep evaluation and its regulation processes has evolved dramatically over the last half-century. Sleep state and the preoccupied view of its obligation to perform positive function for the organism have kept enthusiastic research flourishing. The restoration of macromolecular synthesis and repair players, energy conservation, neural plasticity and synaptogenesis are cellular and biochemical-level functional implications of sleep. The demarcation between molecular, cellular and systemic strata is not mutually exclusive at organism level. Sleep functions have been researched with their focus at each of these strata. The review discusses the systemic-level functions of sleep in brief with special reference to respiration, reproduction, digestion, cardiovascular, endocrine, immune and integumentary systems. Sleep and physiological system relations are usually bidirectional and are operationally mediated by intercellular message transmitters like hormones, cytokines and/or continuum of direct anatomical connections with the neuroanatomy of sleep management.