Eicosanoids, Melatonin, Histamine, Bradykinin, Serotonin (Physiology) Flashcards
What are eicosanoids?(2)
Lipid derived paracrine signals which regulate various physiological functions.
What cleaves the eicosanoids and what is formed when they are cleaved?
They are cleaved by phospholipase A2, and they form arachidonic acid.
Examples of eicosanoids
Thromboxanes, leukotrienes, prostaglandins
What activates phospholipase A2?
Cell swelling and increased intracellular calcium.
What stimulates phospholipase A2? (4)
Histamine, bradykinin, NA, Serotonin
What inhibits phospholipase A2? (2)
Glucocorticoids
Adrenaline
Explain the effects of COX-1.
When there is a physiologic stimulus, COX-1 is produced, which is constitutive.
It acts upon the stomach,kidneys, intestines, platelets and endothelium.
Causes the secretion of PGE2, TxA2, and PGI2, which performs physiologic functions.
Note: this pathway can be inhibited by NSAIDs.
Explain the effects of COX-2.
There will be an inflammatory stimuli.
Stumulates the inducive COX2 to act upon the inflammatory sites.
Causes the production if inflammatory prostaglandins, proteases and reactive oxygen species, which causes inflammation.
What are the functions of leukotrienes and PGF?
-Smooth muscle constriction
-Indirect vascular permeability-oedema
-Adhesion, chemotaxis
- Stimulates release of lysosomal enzymes, O2 radicals, insulin and histamine.
Function of Thromboxane A
Clotting
What are the functions of Prostaglandin E2?
Stimulates contraction of smooth muscle of gut and uterus.
Lipolysis, inhibits production of hormones.
Inhibits contraction of renal vasculature and bronchial muscles.
What is responsible for:
A. Blood clotting
B. Bronchoconstriction
C. Regulation of circadian rhythm
A. Thromboxanes
B. Leukotrienes
C. Melatonin
What are the functions of PGE2 and PGI2? (4)
-Demineralise bone
-Vasodilation
-pain
-Natriuresis and diuresis
Which cells produces histamine?
Tissue mast cells
Basophils
What stimulates the release of histamine?
Burns, inflammation, drugs, IgE.
What inhibits release of histamine?
-PGE2, adrenalin, anti-histamines
What are the effects of histamine in the body? (6)
Causes catecholamines release.
Causes increased secretion of HCL in stomach.
Increases cardiac contractility and rate.
Vasodilation of independent small blood vessels.
Contraction of smooth muscle of uterus, intestines and bronchi.
Increases capillary permeability (oedema).
What are the effects of histamine and bradykinin? (6)
-Bronchospasm
-Oedema
-Abdominal cramps (histamine)
-Drop in blood pressure
-Pain
-Puritis
What are the effects of serotonin in the body? (5)
-Causes smooth muscle contraction of small intestines, bronchi, uterus and blood vessels.
-Can also cause vasodilation.
-Platelets aggregation
-Pain
-Permeability of capillaries
What are the consequences of serotonin?
-Oedema
-Bronchospasm, increased or decreased BP, diarrhoea.
-Pain
-Headaches
