Medical physiology explains how cellular processes scale up to organ and whole-body functions that maintain homeostasis. Volume 1 covers membrane physiology, cellular signaling, excitation–contraction, synaptic transmission, and the neural networks that integrate sensation and motor control. It links ionic mechanisms and receptor biology to reflexes, autonomic regulation, and central control of vital functions. Clear diagrams, equations, and pathway maps help readers translate molecular mechanisms into functional outcomes. Clinical vignettes illustrate how physiological derangements produce common signs and guide diagnostic reasoning.