Briefly explain the main cause or mechanism of the increase in respiratory rate or depth and/or respiratory difficulties in the following cases: (one to two sentences only)
1. Initiation of exercise
- Neural changes that send excitatory impulses to the dorsal respiratory group (DRG) lead to an increase in breathing rate at the start of the exercise. 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 (pre-central gyrus).
2. Moderate exercise
- Meanwhile, the increase in the depth of breathing in moderate exercise is due to chemical and physical changes in the bloodstream. These changes include: (1) slightly decreased PO2; (2) slightly increased PCO2; and (3) increased temperature.
3. Asthma attack
- Possible causes of airway obstruction in asthma include: (a) smooth muscle spasms in the walls of smaller bronchi and bronchioles, (b) edema of the mucosa of the airways, (c) and/or damage to the epithelium of the airway.
4. Abrupt ascent into high altitudes
- Shortness of breath is one of the symptoms of high altitude sickness due to a lower level of oxygen in the blood. As the person abruptly ascents into high altitudes, the alveolar PO2 decreases and O2 diffuses into the blood more slowly.
5. Pneumonia
- Dyspnea or difficulty in breathing is experienced due to toxins released by microbes entering the lungs, stimulating inflammation and immune responses. Inflammation and edema cause the alveoli to fill with fluid while the toxins and immune responses damage alveoli and bronchial mucous membranes.
6. Paralysis of phrenic nerve
- Paralysis of the phrenic nerve is possibly due to pressure from malignant tracheal or esophageal tumors in the mediastinum or severing of the spinal cord above the origin of the phrenic nerves (C3, C4, and C5). As the phrenic nerve innervates the diaphragm, paralysis leads to respiratory arrest or halting breathing.
7. Severe tuberculosis with resulting lung scar tissue
- People experiencing severe tuberculosis have lungs that have low compliance, resisting expansion which leads to difficulty in pulmonary ventilation. It may be due to decreased elasticity and/or increased surface tension that resulted from the inflammation triggered by the Mycobacterium tuberculosis.
8. Severe anemia
- Shortness of breath is one of the most common effects of severe anemia. It is a condition where there is a reduced number of RBCs or decreased amount of hemoglobin in the blood consequently resulting in decreased oxygen levels in the blood needed for organs to function.
9. Advanced COPD (chronic obstructive pulmonary disease)
- The occurrence of COPD is influenced by the presence of cigarette smoke, air pollution, pulmonary infection, occupational exposure to dust and gases, and genetic factors. These contribute to the mentioned respiratory disorder which involves an increase in airway resistance due to chronic and recurrent obstruction of airflow.
10. Advanced pregnancy
- As the uterus begins to press on the diaphragm during pregnancy, full expansion of the lungs will be hard to achieve which leads to shallow breathing or shortness of breath.
References:
Tortora, G. J., & Derrickson, B. H. (2014). Principles of anatomy and physiology (14th ed.). John Wiley & Sons.