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.
A Macrophage is a white blood cell, produced by Monocytes. Monocytes and Macrophages are both Phagocytes. These work as a part of the human immune system. They act in non-spec â¦ ific innate immunity defense and are able to initiate specific cell-mediated immunity. Definition of Macrophage and Its Role in the Body The best definition of macrophage is a white blood cell operating within the body tissues. 2  In humans, macrophages measure approximately 21 micrometers in diameter.