In physiology, a stimulus (plural stimuli) is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity.When a stimulus is applied to a sensory receptor, it normally elicits or influences a reflex via stimulus transduction.he endocrine system is affected largely by many internal and external stimuli. One internal stimulus that causes hormone release is blood pressure. Hypotension, or low blood pressure, is a large driving force for the release of vasopressin, a hormone which causes the retention of water in the kidneys.
Macrophages can be activated by cytokines such as interferon-gamma (IFN-gamma) and bacterial endotoxins, such as lipopolysaccharide (LPS). Activated macrophages undergo many changes which allow them to kill invading bacteria or infected cells.
2010). Resident macrophages become adapted to perform particular functions in different organs; so that brain macrophages (microglia) are very different from alveolar macrophages of the lung, Kupffer cells of the liver, or the largest tissue macrophage population, those lining the wall of the gut.his review is a synthesis of reviews of macrophage biology that I have written over the past 20 years. With apologies to colleagues in the field, the review makes no attempt to provide comprehensive referencing, and refers exclusively to reviews by others for further reading where appropriate.