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Defense physiology is a term used to refer to the symphony of body function changes which occur in response to a stress or threat.. When the body executes the "fight-or-flight" reaction or stress response, the nervous system initiates, coordinates and directs specific changes in how the body is functioning, preparing the body to deal with the threat. [1]
An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.
Complement proteins are proteins that play a role in the non-specific immune responses alongside these non-specific immune cells to make up the first line of immune defense. [4] The non-specific immune response is an immediate antigen-independent response, however it is not antigen-specific. Non-specific immunity results in no immunologic memory.
The physiological changes that occur during the fight or flight response are activated in order to give the body increased strength and speed in anticipation of fighting or running. Some of the specific physiological changes and their functions include: [24] [25] [26]
The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome. [ 30 ] [ 31 ] Phagocytosis evolved as a means of acquiring nutrients , but this role was extended in phagocytes to include engulfment of pathogens as a defense mechanism. [ 32 ]
Cellular immunity protects the body through: T-cell mediated immunity or T-cell immunity: activating antigen-specific cytotoxic T cells that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
Unlike the amoeboid forms of microglia, the cell body of the ramified form remains in place while its branches are constantly moving and surveying the surrounding area. The branches are very sensitive to small changes in physiological condition and require very specific culture conditions to observe in vitro .
Intrinsic immunity refers to a set of cellular-based anti-viral defense mechanisms, notably genetically encoded proteins which specifically target eukaryotic retroviruses. Unlike adaptive and innate immunity effectors, intrinsic immune proteins are usually expressed at a constant level, allowing a viral infection to be halted quickly.