Final answer:
During hypoxia, the VRG in the medulla oblongata increases ventilation by stimulating accessory muscles for forced breathing, thus enhancing oxygen intake to counteract the reduced oxygen levels in the blood.
Step-by-step explanation:
The action of the ventral respiratory group (VRG) during hypoxia, which is a condition characterized by an insufficient amount of oxygen reaching the tissues, is to increase ventilation in order to meet the body's increased oxygen demand. When hypoxia occurs, sensors such as the carotid body detect the low oxygen concentration and send signals to the respiratory centers in the medulla, specifically the VRG. The VRG then activates the accessory muscles involved in forced inspiration and expiration, resulting in increased breathing rate and volume. This is part of a negative feedback loop that aims to restore homeostasis by increasing oxygen intake during events like exercise, high altitude exposure, or any situation that reduces oxygen levels in the blood.