1. What are chemical mediators
These are the substances that INITIATE & REGULATE Inflammatory reactions.
2. Describe the general properties of chemical mediators
a. These mediators can be produced Locally, by the CELLS and are called CELL- DERIVED. / Derived from inactive precursors present in plasma which are referred to as PLASMA -DERIVED . The cell derived mediators are preformed mediators where as the plasma derived are the ones which are synthesized de-novo.
b. They can be produced only in response to agents that stimulate inflammation
c. They can stimulate the release of another mediator.
d. They have short lifespan: as they are degraded by enzymatic action very rapidly.
e. They can act on wide variety of cells and may have similar action on different targets or different actions on similar targets.
3. Classify chemical mediators
The chemical mediators are classified as shown in the illustration below.
4. Write a note on Histamine and serotonin
These are Vasoactive amines. They are the first mediators to be released during inflammation. Once formed it can be either stored or rapidly inactivated. Derived from the decarboxylation of the amino acid histidine.
The sources and stimuli for the release of histamine are as illustrated in the diagram below
5. Mention the actions of Histamine
The actions of histamine are as below
a. Increase in Vascular permeability By Increasing Blood Flow and Endothelial Barrier Disruption
b. Cause vasodilation by stimulating the release of nitric oxide
c. The above two are responsible for the Wheal & Flare reaction in the skin
d. It is Responsible for itching and pain. This is brought about by the excitation of a subset of unmyelinated C-fibers which are pruriceptive
e. Also mediates bronchial Asthma and anaphylactic shock by Contraction of extravascular smooth muscles.
6. Write a note on serotonin
It is 5- Hydroxytryptamine. Stored in platelets and mast cells. Also in chromaffin cells of GIT, spleen and nervous tissue. A
The actions are similar to Histamine but less potent.
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