<P> Physiology (/ ˌfɪziˈɒlədʒi /; from Ancient Greek φύσις (physis), meaning' nature, origin', and - λογία (- logia), meaning' study of') is the scientific study of normal mechanisms, and their interactions, which works within a living system . A sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system . Given the size of the field, it is divided into, among others, animal physiology (including that of humans), plant physiology, cellular physiology, microbial physiology (microbial metabolism), bacterial physiology, and viral physiology . </P> <P> Central to an understanding of physiological functioning is its integrated nature with other disciplines such as chemistry and physics, coordinated homeostatic control mechanisms, and continuous communication between cells . </P>

The study of the coordinated functions of a living organism is called