252 OLIVE OILS AND HEALTH GLUCOCORTICOID/S (See PHYSIOLOGY / Endocrine system / Hormones / Corticosteroids) GLUTAMATE Glutamic acid, either in its free form or in its ionised form L-glutamate (GLU), is one of the most abundant amino acids in nature. It serves multiple functions and has various applications. In the nervous system, it facilitates and accelerates communication between nerve cells (neurons), and it has been associated with both short- and longterm enhancement of memory and learning. In the intestine and liver, it acts as a source of energy and serves as a precursor for biologically significant molecules. Glutamate, or its monosodium salt, is also used as a food additive, as it imparts the flavour known as “umami” (a Japanese word meaning “tasty” or “savoury”). Its use in food has been recognised as safe by various organisations responsible for evaluating the safety of food additives. GLYCATED HAEMOGLOBIN (See DIABETES MELLITUS) GLYCERIDE/S (See LIPIDS / Concepts) GLYCOGEN (See METABOLISM) GLYCOSYLATED HAEMOGLOBIN (See DIABETES MELLITUS) HAEMOSTASIS; VASCULAR HAEMOSTASIS; HAEMOSTATIC SYSTEM Haemostasis is the sequence of physiological events that occur to prevent and stop bleeding when blood vessels are injured. The immediate reaction is vasoconstriction, or narrowing of the affected vessel, which helps to reduce blood flow and minimise blood loss. This is followed by clot formation, tissue repair, and ultimately the dissolution of the clot when it is no longer needed. Under normal physiological conditions, these mechanisms maintain a delicate balance; disruption of this balance can lead to pathological conditions such as bleeding or thrombosis. Thanks to haemostasis, the integrity of the circulatory system is preserved, keeping it closed and maintaining blood pressure following vascular injury. Haemostasis is divided into primary and secondary phases. - primary haemostasis Primary haemostasis refers to the processes by which a platelet plug is formed through platelet adhesion, activation, secretion, and aggregation. Clots are composed of various blood components: platelets, red blood cells, and specific proteins known as coagulation factors (most of which are produced by endothelial cells). All these factors circulate in the bloodstream, ready to act at the site of vessel injury. - secondary haemostasis Secondary haemostasis involves the activation of the enzymatic coagulation cascade, in which coagulation factors interact on the surfaces of platelets and endothelial cells to generate thrombin. Thrombin converts fibrinogen into fibrin, forming fibrin strands
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