<Tr> <Td> </Td> <Td> This section includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations . Please help to improve this section by introducing more precise citations . (January 2012) (Learn how and when to remove this template message) </Td> </Tr> <P> The dorsal respiratory group is involved in the generation of the respiratory rhythm, and is primarily responsible for the generation of inhalation . It is also stimulated via the apneustic centre in the lower pons and is also a part of the solitary tract, which is responsible for appropriating responses to sensory information from chemoreceptors and mechanoreceptors in humans . It is inhibited by the pneumotaxic centre . </P> <P> Inhalation or inspiration, begins when cells of the solitary tract nucleus (along with cells of the ventral respiratory group) 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 . </P> <P> The rhythm of the DRG produces a respiratory rate of 12--16 breaths per minute in humans . Inhalation usually lasts approximately 2 seconds, and exhalation lasts about 3 seconds . The normal respiratory rhythm is called eupnea, and difficult respiration is termed dyspnea . </P>

Which center stimulates inspiration by increasing the activity of the dorsal respiratory group (drg)
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