During exercise, the adrenal medulla and sympathetic nerves cause which of the following to occur?
Precapillary sphincters constrict in response to muscle metabolites such as lactic acid, CO2, and adenosine.
Arterioles dilate in response to epinephrine and norepinephrine.
Muscles contract to compress the blood vessels.
Parasympathetic nerves are activated.
The Correct Answer is B
Choice A rationale
During exercise, local accumulation of metabolic byproducts like lactic acid, carbon dioxide, and adenosine in active muscles causes vasodilation, not constriction, of precapillary sphincters and arterioles. This vasodilation increases blood flow to meet the increased metabolic demand.
Choice B rationale
During exercise, the adrenal medulla releases epinephrine and norepinephrine, and sympathetic nerves release norepinephrine. These catecholamines cause widespread vasoconstriction in inactive tissues but induce vasodilation in skeletal muscles through specific receptor activation (beta-2 adrenergic receptors), increasing blood flow to working muscles.
Choice C rationale
Muscle contraction does compress blood vessels, aiding venous return (skeletal muscle pump). However, this is a mechanical action aiding circulation, not the direct effect of adrenal medulla and sympathetic nerves on arteriolar diameter in response to exercise, which primarily involves neurochemical regulation.
Choice D rationale
During exercise, the sympathetic nervous system is highly activated, leading to a "fight or flight" response. Conversely, the parasympathetic nervous system, which promotes "rest and digest" functions, is generally inhibited or its activity is decreased, not activated, to allow for increased cardiac output and blood flow to muscles.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
Natural active immunity occurs when an individual's immune system produces its own antibodies and memory cells after direct exposure to a pathogen through natural infection. Vaccination, while stimulating an active response, is not considered "natural" exposure.
Choice B rationale
Artificial active immunity is stimulated by vaccination. Vaccines introduce weakened, inactivated, or components of pathogens into the body, prompting the immune system to produce its own antibodies and memory cells without causing the disease, thereby conferring long-term protection.
Choice C rationale
Natural passive immunity involves the transfer of antibodies from one individual to another, such as from mother to fetus via the placenta or through breast milk. This provides immediate but temporary protection and does not stimulate the recipient's immune system to produce its own antibodies.
Choice D rationale
Artificial passive immunity involves the direct administration of pre-formed antibodies (e.g., antitoxins, immunoglobulins) to an individual. This provides immediate, temporary protection and is used for acute exposures or in immunocompromised individuals; it does not stimulate active immunity.
Correct Answer is E
Explanation
Choice A rationale
The spleen is primarily involved in filtering blood, removing old red blood cells, and housing immune cells. While it plays a role in blood storage and immune responses, it is not a primary site for the synthesis of most clotting factors, which are complex proteins.
Choice B rationale
Red bone marrow is the primary site of hematopoiesis, the production of all blood cells, including platelets, erythrocytes, and leukocytes. However, it does not synthesize most of the plasma clotting factors; rather, it produces the cellular components involved in coagulation.
Choice C rationale
Perivascular tissue surrounds blood vessels and contains various cell types, including fibroblasts and adipocytes. While these tissues can contribute to local inflammatory responses or tissue repair, they are not major sites for the systemic synthesis of plasma clotting factors.
Choice D rationale
The kidneys play a vital role in blood filtration, waste excretion, and regulation of blood pressure and erythropoiesis (via erythropoietin). However, the kidneys do not synthesize the majority of the plasma clotting factors required for hemostasis.
Choice E rationale
The liver is the primary site for the synthesis of most plasma clotting factors, including fibrinogen, prothrombin, and factors V, VII, IX, X, and others. Hepatocytes in the liver are responsible for the complex protein synthesis required for the coagulation cascade, making it critical for hemostasis.
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