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 D
Explanation
Choice D rationale
Hyposecretion, or inadequate hormone release, can indeed result from a combination of factors. Tumors or lesions directly destroying glandular tissue (primary hyposecretion), interference with the gland's ability to receive stimulating signals (secondary hyposecretion), or inadequate trophic hormone stimulation from a higher center all lead to insufficient hormone production.
Choice A rationale
Tumors or lesions that destroy an endocrine gland directly impair its ability to synthesize and secrete hormones, leading to primary hyposecretion. For example, damage to pancreatic islet cells can cause insufficient insulin production, leading to diabetes mellitus.
Choice B rationale
Tumors or lesions that interfere with a gland's ability to receive signals from another gland, such as the pituitary, result in secondary hyposecretion. If the adrenal cortex cannot respond to ACTH due to receptor damage, it will not produce sufficient corticosteroids.
Choice C rationale
Inadequate stimulation of the gland, such as insufficient release of a trophic hormone from the pituitary or hypothalamus, leads to insufficient hormone production. For example, if the pituitary does not release enough TSH, the thyroid gland will exhibit hyposecretion of thyroid hormones.
Correct Answer is A
Explanation
Choice A rationale
The pericardial fluid is a serous fluid found within the pericardial cavity, which is the space situated between the visceral pericardium (epicardium), directly adhering to the heart's surface, and the outer parietal pericardium. This fluid acts as a lubricant, reducing friction during cardiac contractions.
Choice B rationale
The myocardium is the thick muscular layer of the heart wall, and the epicardium is the visceral layer of the serous pericardium, directly covering the myocardium. There is no fluid-filled space between these two layers; they are directly continuous.
Choice C rationale
The endocardium is the innermost lining of the heart chambers, and the myocardium is the muscular layer. These layers are directly contiguous, forming the wall of the heart, without any fluid-filled space between them.
Choice D rationale
The heart and lungs are distinct organs within the thoracic cavity. While they are in close proximity, the pericardial fluid is specific to the sac surrounding the heart, not a general fluid space between the heart and the lungs.
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