kris2c
Forum Senior
Topics: 30
Posts: 108
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A healthy 28-year-old woman stands up from a supine position. Which of the following cardiovascular changes is most likely to occur?
A. Decreased myocardial contractility
B. Decreased total peripheral resistance
C. Dilation of large veins
D. Increased heart rate
E. Increased renal blood flow
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Kris2c
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B. Decreased total peripheral resistance
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Decrease total peripheral resistance
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| cprax
Forum Junior
Topics: 13
Posts: 54
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Increased heart rate
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| auubar
Forum Senior
Topics: 30
Posts: 182
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I will choose increased heart rate.
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| kris2c
Forum Senior
Topics: 30
Posts: 108
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The correct answer is D.
The baroreceptor mechanism is important for maintaining arterial pressure when a person sits or stands from a lying position.
When a person suddenly stands, the blood pressure in the brain and upper body tends to fall, which initiates a strong sympathetic discharge throughout the body aimed at returning blood pressure to normal. ---> Increasing sympathetic stimulation to the heart causes an increase in heart rate, conduction velocity, and myocardial contractility (compare with choice A).
The sympathetic stimulation also causes constriction of nearly all the arterioles in the body, which greatly increases the total peripheral resistance (compare with choice B).
Sympathetic stimulation of the renal vasculature leads to a decrease in renal blood flow (compare with choice E).
Constriction of large veins (compare with choice C) increases venous return to the heart, causing the heart to pump increased amounts of blood.
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Kris2c
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