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 A
Explanation
Red blood cells do not contain a large nucleus; in fact, they do not contain a nucleus at all when they are mature.
This is an adaptation that allows them to carry more hemoglobin, the protein that binds oxygen, and to squeeze through narrow capillaries.
Choice B is wrong because it contradicts the fact that red blood cells are enucleated (lacking a nucleus) in humans and most mammals.
Some vertebrates, such as birds and fish, have nucleated red blood cells, but they are not thick near the center and thin around the rim of the cell.
Correct Answer is A
Explanation
This is because ventricular systole is the phase of the cardiac cycle when the ventricles contract and pump blood into the arteries.
The blood pressure in the arteries is greatest during this phase because of the forceful ejection of blood.
Choice B.
Atrial diastole is wrong because atrial diastole is the phase of the cardiac cycle when the atria relax and fill with blood from the veins.
The blood pressure in the arteries is lowest during this phase because the ventricles are also relaxed and not pumping blood.
Choice C.
Ventricular diastole is wrong because ventricular diastole is the phase of the cardiac cycle when the ventricles relax and fill with blood from the atria.
The blood pressure in the arteries is low during this phase because the ventricles are not pumping blood.
Choice D.
Atrial systole is wrong because atrial systole is the phase of the cardiac cycle when the atria contract and push blood into the ventricles.
The blood pressure in the arteries is not affected by this phase because the ventricles are still relaxed and not pumping blood.
The normal range for systolic blood pressure is less than 120 mm Hg and for diastolic blood pressure is less than 80 mm Hg.
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