| A | B |
|---|
| most concentrated areas of mast cells | blood vessels, internal surfaces, feet, GI tract, nose, mouth |
| areas containing hon mast cell histamine | brain, enterochromaffin-like cells of fundus of stomach |
| where is most tissue histamine found | mast cells and basophils; exists in bound form in granules |
| immunologic release | IgE sensitized -> Ag stimulated degranulation; rqrs Ca++ and ATP |
| negative feedback for histamine | skin and blood |
| histamine release causes a decrease in the function of *** | B and T cells |
| vascular effects of histamine | local vasodialator and leakage of plasma |
| degranulation causes release of *** | histamine, ATP, and other inflam mediators |
| degranulation promotes *** (esp ATP) | more degranulation |
| chemical causes of histamine release | curare neuromuscular blockers, morphine |
| does not rqr E, not assd with mast cell injury or degranulation | chemical and mechanical release |
| H1 receptor subtype distribution | sm. muscle, endothelium, brain |
| H2 receptor subtype distribution | gastric mucosa, cardiac muscle, mast cells, brain |
| H3 receptor subtype distribution | presynaptic brain, myenteric plexus, other neurons |
| subtype receptor that causes "wheal and flare" histamine rxn | H1 |
| subtype receptor that causes dec neurotransmitter rls | H3 |
| histamine effect on CV | dec. BP, inc. HR, flushing, warmth, headach, edema |
| histamine effect on GI tract | sm. muscle contraction, diarrhea (H1) |
| other areas of sm. muscle assd. with histamine effect | eye, GU tract (can cause abortion) |
| bronchiolar sm. muscle effect of histamine | bronchoconstriction (H1) |
| histamine effect on nerve endings | mediates pain and itching (H1) |
| triple response | -> wheal and flare; redness, wheal, flare |
| to block triple response | H1 and H2 inhibitors |
