In the immediate response to blood loss, what does constriction of the veins achieve?

1. Falling blood pressure slows baroreceptor firing, and the cardiovascular centers answer with sympathetic outflow. 2. That outflow constricts arterioles, which raises vascular resistance. 3. It also constricts veins, and venous constriction increases venous return to the heart. 4. Greater venous return raises preload, so each contraction ejects more blood. 5. Sympathetic drive simultaneously releases epinephrine and norepinephrine, which raise cardiac output further, so option B has the direction backwards. 6. Heart rate climbs rather than settling, reaching 180 to 200 contractions per minute in this response. 7. If blood loss stays under 20 percent of total volume, these steps usually restore blood pressure without transfusion. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 20 "The Cardiovascular System: Blood Vessels and Circulation", section 20.4 Homeostatic Regulation of the Vascular System_