Normal defenses: skin, mucus, hair, hcl, host flora in gut, ear wax. Inflammation body"s defense to destroy (generic) pathogens. Occurs for a variety of reasons (allergies, injury, infection etc. ) Acute (8-10 days) danger of !anaphylaxis. Exudation of fluid and plasma and emigration of leukocytes into extravascular tissues. Chronic (persistent) lupus, arthritis, celiac"s, ms . Presence of lymphocytes and macrophages, proliferation of blood vessels, fibrosis and tissue necrosis/scar formation: vascular phase. Leukotrienes = vasodilation, vascular permeability: cellular phase. Neutrophils at site of injury: adhesion and margination, transmigration. Complementary adhesion molecule (selectins, integrins) facilitate migration to extravascular tissue: chemotaxis (leukocytes migrate to site of injury) Found in: vascular endothelial cells, smooth muscle (bronchoconstriction), brain (wakefulness, appetite suppression), peripheral nerve endings (itch: h2 receptor stimulation: acid secretion, +ve chronotropy ( hr) Poor h1 receptor selectivity and can occupy other receptors (cholinergic, -adrenergic, serotonin s/e: dry mouth, uriticaria, hypotension, reflex tachycardia, increased appetite) Blockade of central histamine and ach receptors cause antiemetic effects.