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 A
Explanation
Choice A rationale
Oxygen-poor blood from the systemic circulation enters the right atrium, then passes through the right AV (tricuspid) valve into the right ventricle. From the right ventricle, it is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. This pathway ensures deoxygenated blood reaches the pulmonary circuit.
Choice B rationale
This choice is incomplete because while oxygen-poor blood does pass through the right AV (tricuspid) valve, it must also pass through the pulmonary valve to exit the right ventricle and reach the lungs for oxygenation. Omitting the pulmonary valve provides an incomplete description of the path.
Choice C rationale
The left AV (mitral) valve and aortic valve are components of the left side of the heart, which handles oxygenated blood. Oxygenated blood from the lungs enters the left atrium, passes through the mitral valve into the left ventricle, and then through the aortic valve into the aorta for systemic distribution.
Choice D rationale
This choice describes only the entry of oxygenated blood into the left ventricle from the left atrium via the left AV (mitral) valve. It does not account for the oxygen-poor blood pathway, which involves the right side of the heart.
Choice E rationale
The pulmonary valve allows oxygen-poor blood to leave the right ventricle. However, the aortic valve allows oxygenated blood to leave the left ventricle. Therefore, the combination of pulmonary and aortic valves does not exclusively describe the path of oxygen-poor blood.
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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