Final answer:
In early shock, stroke volume is maintained by increased sympathetic stimulation. This response elevates the heart rate, enhances vasoconstriction, and facilitates the release of epinephrine and norepinephrine to restore cardiac output and blood pressure, especially when blood loss is less than 20 percent of total volume.
Step-by-step explanation:
Stroke volume may be maintained in early shock by increased sympathetic stimulation. This stimulation prompts a series of physiological responses that work to counteract the effects of shock, such as blood loss, and sustain vital organ function. When the body goes into shock, the sympathetic nervous system increases the heart rate to about 180-200 contractions per minute, restoring cardiac output to normal levels in response to decreased blood pressure.
Vasoconstriction of the arterioles increases vascular resistance, and constriction of the veins enhances venous return to the heart. Furthermore, the release of epinephrine and norepinephrine boosts both cardiac output and vasoconstriction. If the blood loss is less than 20 percent of the total blood volume, these combined actions can normalize blood pressure and ensure that the remaining blood is efficiently circulated to the body's tissues.