which center stimulates inspiration by increasing the activity of the dorsal respiratory group (drg)
Dorsal respiratory group Inhalation or inspiration, begins when cells of the solitary tract nucleus (along with cells of the ventral respiratory group)[citation needed] begin a steady increase in firing, leading to contraction of the respiratory muscles. When neurons in the DRG are activated they send impulses down the phrenic and intercostal nerves to stimulate the diaphragm and external intercostal muscles. The thoracic cavity expands and air rushes into the lungs due to the negative pressure, producing inspiration. When the cells stop firing, the respiratory muscles relax, inhalation ceases, and exhalation begins.
Respiratory tract In humans, the respiratory tract is the part of the anatomy of the respiratory system involved with the process of respiration. Air is breathed in through the nose or the mouth. In the nasal cavity, a layer of mucous membrane acts as a filter and traps pollutants and other harmful substances found in the air. Next, air moves into the pharynx, a passage that contains the intersection between the esophagus and the larynx. The opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway.