1. Initiation of exercise
- Respiratory rate and depth increases in response to signals from proprioceptors, which observe joint and muscle motion, as well as simultaneous excitatory impulses from upper motor neurons rooted in the primary motor cortex. These combined signals activate the DRG in the medulla and trigger the immediate adjustments in respiratory effort, happening before any changes in oxygen, carbon dioxide, or hydrogen ion levels are noticed.
2. Moderate exercise
- The signals from proprioceptors and chemoreceptors, which activate the medullary respiratory centers, are the cause of the increased breathing rate and depth during moderate exercise. These centers then send nerve impulses to the respiratory muscles, causing them to breathe more quickly and vigorously in order to fulfill the body's increased demand for oxygen and effectively expel excess carbon dioxide.
3. Abrupt ascent into high altitudes
- Reduced oxygen levels in the atmosphere cause peripheral chemoreceptors to become activated during sudden ascent to high altitudes, triggering the brain's medullary respiratory centers. In order to counter the lower oxygen availability and maintain adequate oxygen in the body, these centers boost nerve impulses to the respiratory muscles, resulting in an increased respiratory rate and depth of breathing.
4. Paralysis of phrenic nerve
- The paralysis of the phrenic nerve impairs the function of the primary respiratory muscle, the diaphragm. Due to the decreased diaphragmatic movement, respiratory muscles must work harder, which can cause breathing difficulties and reduced oxygenation.
5. Severe anemia
- Hypoxia can result from severe anemia when the blood's ability to carry oxygen is reduced. The body attempts to improve oxygen uptake from the limited supply of oxygen-rich hemoglobin by increasing respiratory rate and depth in an effort to make up for this oxygen shortage.
6. Advanced pregnancy
- In advanced pregnancy, higher progesterone levels make the respiratory center more sensitive to carbon dioxide, which raises the respiratory rate and depth. Additionally, the restricted breathing caused by the growing fetus and the elevated diaphragm causes the mother's respiratory rate to increase in order to meet the growing fetus's oxygen needs.