circadian, metabolism, melatonin, wakefulness, metabolic, serotonin, pineal gland, autonomic nervous system, rem sleep, photoperiodic, gluconeogenesis, neurotransmission, catecholamine, chronobiology, parasympathetic nervous system, diurnal, neurohormone, parasympathetic, neuroendocrine, sleep, homeostasis, physiological, rhythmicity, neurochemistry, intestinal flora, thyroid hormone, melanocyte, hormonal, glucocorticoid, autoregulation, sleepiness, mitochondria, corticosterone, basal metabolism, synchrony, cortisol, oxidative phosphorylation, menstrual cycle, nrem, plasticity, synaptic, pineal, myelination, thermoregulation, hyperphagia, diapause, vasopressin, luteinizing hormone, neurotransmitter, spermatogenesis, photoreceptor, proteolysis, calmodulin, striated muscle, embryogenesis, basal metabolic rate, excitability, leucine, endocrine, hormone, hypersomnia, cognition, neuromuscular junction, physiology, ghrelin, neurogenesis, cytoskeleton, secretion, rhodopsin, hypothalamic, monoamines, adrenals, thyrotropin, metabolic pathway, osmolality, arginase, nrem sleep, cholinergic, dopamine, phosphorylation, diurnal variation, neuropeptide, adrenal cortex, estrous cycle, metabolise, astrocyte, epigenetic, thermogenesis, blood sugar, peristalsis, genes, nadh, glutathione, amino acid, neurons, ciliary, alertness, innate immunity, hypoxia, hypothalamus, catabolism, oscillations

biological time