The velocity of blood flow decreases when
vessel radius increases
afterload increases
blood pressure increase
vasomotion decreases
The Correct Answer is B
A. Vessel radius increases: Increasing the radius of a blood vessel reduces resistance and allows blood to flow more easily. According to Poiseuille’s law, a larger radius increases flow velocity, so this does not decrease velocity.
B. Afterload increases: Afterload is the resistance the heart must overcome to eject blood. An increase in afterload slows the ejection of blood from the ventricles, reducing the velocity of blood flow through the arterial system.
C. Blood pressure increases: Higher blood pressure creates a greater driving force for blood, which generally increases flow velocity rather than decreasing it.
D. Vasomotion decreases: Vasomotion refers to the rhythmic constriction and dilation of arterioles. A decrease in vasomotion may reduce perfusion regulation but does not directly decrease velocity in large vessels as significantly as an increase in afterload does.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Lymph nodes:Lymph nodes serve as sites where B lymphocytes encounter antigens and become activated, but they do not confer immunocompetence. They primarily function in filtering lymph and supporting the immune response rather than the initial development of B cells.
B. Spleen:The spleen acts as a secondary lymphoid organ where B cells can encounter blood-borne antigens and participate in immune responses. However, it does not provide the environment for B cells to acquire immunocompetence initially.
C. Thymus:The thymus is essential for T lymphocyte maturation and development of immunocompetence, but it is not involved in B cell maturation. B cells do not pass through the thymus during their development.
D. Bone marrow:B lymphocytes develop immunocompetence in the bone marrow, where they undergo differentiation and selection processes to ensure functional antigen receptors. This primary lymphoid organ provides the necessary environment for B cells to acquire the ability to recognize specific antigens before entering circulation.
Correct Answer is D
Explanation
A. Booster shot of vaccine:A booster shot stimulates the body’s own adaptive immune system to produce antibodies and memory cells. This is an example of active immunity, not passive immunity, because the immune response is generated by the individual.
B. Exposure to an antigen:Natural exposure to an antigen triggers the body to mount an immune response and develop memory cells. This is a form of active immunity, as the individual’s immune system actively responds to the pathogen.
C. Infusion of weakened viruses:Infusion of weakened viruses (live attenuated vaccines) stimulates active immunity by inducing the body to produce its own antibodies and memory cells. It does not confer immediate passive protection.
D. Passage of IgG antibodies from a pregnant mother to her fetus:Passive immunity occurs when preformed antibodies are transferred from one individual to another. Maternal IgG crosses the placenta to provide the fetus with temporary protection against pathogens without requiring the fetus to generate its own immune response.
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