As a result of the allergen-antibody reaction, mast cells release histamine:
False
True
The Correct Answer is B
As a result of the allergen-antibody reaction, mast cells release histamine.
This is because when mast cells are exposed to an allergen that binds to IgE antibodies attached to their FcɛRI receptors, they release histamine and other inflammatory mediators.
Histamine causes vasodilation, increased capillary permeability, mucus secretion, and smooth muscle contraction, which result in allergic symptoms such as itching, swelling, sneezing, and wheezing.
Mast cells do release histamine in response to allergen-antibody reactions. Some additional sentences are:
Normal ranges of histamine levels vary depending on the tissue and the method of measurement, but they are usually low in healthy individuals and elevated in allergic conditions.
Histamine can be degraded by enzymes such as diamine oxidase and histamine N- methyltransferase, or inhibited by drugs such as antihistamines.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
This sequence ensures that the atria contract before the ventricles and that the ventricles contract from the bottom up.
Choice A is wrong because it reverses the order of the SA node and the AV node. The SA node is the pacemaker of the heart and initiates the cardiac impulses.
Choice B is wrong because it places the Purkinje fibers before the AV node.
The Purkinje fibers are the last part of the conduction system and stimulate the ventricular muscle fibers.
Choice D is wrong because it reverses the order of the entire sequence.
The AV node is not the pacemaker of the heart and does not initiate cardiac impulses.
Correct Answer is D
Explanation
This helps prevent blood pooling and clotting in the lower extremities, which can lead to deep vein thrombosis and pulmonary embolism.
It also reduces the workload on the heart and improves blood circulation throughout the body.
Choice A is wrong because contraction of muscles does not stimulate the arteries to vasodilate, but rather causes vasoconstriction in the inactive tissues to divert blood flow to the active muscles.
Choice B is wrong because the contraction of muscles itself does not increase heart rate significantly unless it is part of an aerobic exercise that elevates the metabolic demand.
Burning calories and keeping the heart strong are benefits of regular physical activity, not occasional muscle contraction.
Choice C is wrong because contraction of the leg muscles does not stimulate baroreceptors, which are pressure-sensitive receptors located in the walls of the arteries.
Baroreceptors respond to changes in blood pressure and signal the autonomic nervous system to adjust heart rate and vascular resistance accordingly.
Contraction of the leg muscles does not affect blood pressure or heart rate directly but rather assists with venous return.
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