A healthy 28-year old woman stands up from a supine position. Which of the following cardiovascular changes is MOST likely to occur?
The baroreceptor mechanism is impoant for maintaining aerial 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 hea causes an increase in hea rate, conduction velocity, and myocardial contractility. The sympathetic stimulation also causes constriction of nearly all the aerioles in the body, which greatly increases the total peripheral resistance. Sympathetic stimulation of the renal vasculature leads to a decrease in renal blood flow. Constriction of large veins increases venous return to the hea, causing the hea to pump increased amounts of blood.
Decreased myocardial contractility
Decreased total peripheral resistance
Dilation of large veins
Increased hea rate