Topic overview

Start with the big picture

Aging is multifactorial rather than a change in one organ alone. Cellular processes include telomere shortening, accumulated DNA damage, epigenetic drift, and impaired autophagy, alongside increased oxidative stress. Across organ systems, common patterns include reduced cardiovascular responsiveness and arterial compliance, changes in pulmonary and renal function, shifts in endocrine signaling, and losses in muscle and bone. The nervous and immune systems also change, while skin, sensory function, and thermoregulation may be affected. These patterns help explain why physiologic reserve can decline with age, but they do not mean every function changes in the same way: some measures, such as basal cognition and thyroid hormone levels, may be relatively preserved. The full lesson connects these changes with homeostasis, sleep, and pharmacokinetics.