Briefly explain the main cause or mechanism of increase in respiratory rate or depth and/or respiratory difficulties in the following cases: (one to two sentences only)
1. Initiation of exercise – At the onset of exercise, an abrupt increase in breathing is due to neural changes that send excitatory impulses to the dorsal respiratory group (DRG) of the medullary respiratory center in the medulla. These changes include: (1) anticipation of the activity, which stimulates the limbic system; (2) sensory impulses from proprioceptors in muscles, tendons, and joints and (3) motor impulses from the primary motor cortex (precentral gyrus).
2. Moderate exercise – there is gradual increase in breathing during moderate exercise due to chemical and physical changes in the bloodstream. These changes include: (1) slightly decreased PO2, due to increased O2 consumption; (2) slightly increased PCO2, due to increased CO2 production due to muscle metabolism; and (3) increased temperature, due to liberation of more heat as more O2 is utilized.
3. Asthma attack – obstruction of airways in asthmas may be due to smooth muscle spasms in the walls of smaller bronchi and bronchioles, edema of the mucosa of the airways, increased mucus secretion, and/or damage to the epithelium of the airway. Any of these 3 mechanisms may cause difficulty in breathing.
4. Abrupt ascent into high altitudes – the total amount of atmospheric pressure decreases as altitude increases, as a result, alveolar PO2 decreases and O2 diffuses into the blood more slowly. VRG becomes activated during forceful inhalations in high altitudes to maintain enough amount of O2 in the blood.
5. Pneumonia – when microbes enter the lungs, it can cause inflammation of the alveoli and damage the bronchioles. Inflammation and edema cause the alveoli to fill with fluid, interfering with ventilation and gas exchange.
6. Paralysis of phrenic nerve – The phrenic nerve innervates the diaphragm which is the most important muscle of inhalation. Paralysis of phrenic nerve may severely affect the function of the diaphragm, greatly reducing its breathing capacity.
7. Severe tuberculosis with resulting lung scar tissue – tuberculosis occurs when a bacteria enter the lungs and cause inflammation. The scar tissue permanently thickens and induces the loss of elasticity of lung tissues, impairing its ability in providing needed gases in the body.
8. Severe anemia – deficiency of red blood cells means not enough hemoglobin to transport oxygen from the lungs to the tissues. Failure of hemoglobin to carry its normal complement of O2 may result to breathing difficulties.
9. advanced COPD (chronic obstructive pulmonary disease) – It occurs when the lungs and airways become damaged and inflamed due to prolonged smoking or immersion in air pollution. When airways are thickened, less oxygen can make it to the bloodstream, resulting in shortness of breath or difficulty breathing.
10. Advanced pregnancy – advanced pregnancies prevent the complete descent of the diaphragm; thus, less volume of air is able to enter the lungs because the maximum capacity of thoracic cavity is lessened, resulting to increased respiratory rate to compensate the lesser maximum capacity of air in the lungs during pregnancy.