Question

why does exercise increase venous return? multiple choice 29.24 the increase in respiratory rate and depth inhibits the action of the thoracic pump. muscle contractions decrease venous return by means of the skeletal muscle pump. blood vessels of the skeletal muscles, lungs, and coronary vessels constrict, increasing pressure

Explanation:

First, analyze each option:

1. The first option says respiratory rate/depth inhibits the thoracic pump, but actually, increased respiration enhances the thoracic pump (which helps venous return), so this is wrong.
2. The second option claims muscle contractions decrease venous return, but the skeletal muscle pump (from muscle contractions) actually increases venous return by squeezing veins, so this is incorrect.
3. The third option: During exercise, blood vessels in skeletal muscles, lungs, and coronary vessels constrict? Wait, no—actually, during exercise, skeletal muscle arterioles dilate (but veins: muscle contractions (skeletal muscle pump) and vasoconstriction in non - working areas (to redirect blood) can increase venous pressure, promoting return. Wait, maybe the option's wording: when exercise occurs, blood vessels in non - essential areas constrict, increasing pressure that drives venous return. Wait, the other options are clearly wrong. The first option's "inhibits thoracic pump" is wrong (thoracic pump is enhanced by respiration). The second option's "decrease" is wrong (skeletal muscle pump increases). So the third option, though wording about constriction (maybe of veins or non - working arteries) to increase pressure for venous return, is the only plausible one among the three. Wait, maybe I misread. Wait, the question is why exercise increases venous return. Let's recall: Venous return is increased by skeletal muscle pump (muscle contractions squeeze veins, pushing blood back), thoracic pump (respiration: inspiration increases thoracic volume, decreasing pressure, drawing blood into thorax), and venoconstriction (sympathetically mediated, constricting veins to increase pressure gradient). So the first option: "inhibits thoracic pump" is wrong—respiration increases thoracic pump. Second option: "decrease venous return" is wrong—skeletal muscle pump increases it. Third option: "blood vessels... constrict, increasing pressure"—venoconstriction increases venous pressure, driving more blood back. So among the three, the third option is correct (the other two have wrong statements).

Answer:

The option "Blood vessels of the skeletal muscles, lungs, and coronary vessels constrict, increasing pressure" (the third option in the list).