POST-LECTURE ACTIVITY: RESPIRATORY SYSTEM
INITIATION OF EXERCISE
- Following the onset of exercise, the dorsal respiratory group (DRG) of the medullary respiratory center in the medulla receives excitatory impulses from neural alterations, which cause a brief upsurge in respiration followed by a more progressive escalation in respiratory rate. The neural alterations encompass the following: (1) the limbic system is stimulated by anticipation of the activity; (2) proprioceptors in muscles, tendons, and joints provide sensory impulses; and (3) the primary motor cortex (precentral gyrus) generates motor impulses.
MODERATE EXERCISE
- The gradual rise in respiratory rate during moderate exercise can be attributed to physical and chemical modifications in the bloodstream: (1) partially reduced PO2 due to heightened O2 consumption; (2) slightly increased PCO2 as a result of raised CO2 production by muscle fiber contraction; and (3) elevated body temperature as an outcome of elevated heat release with increased O2 utilization.
ABRUPT ASCENT INTO HIGH ALTITUDES
- The rate of O2 diffusion into the bloodstream is decreased during an abrupt ascent to high altitude due to a decline in total atmospheric pressure, partial pressure of O2, PO2 of inhaled air, and alveolar PO2. Peripheral chemoreceptors detect a depleted oxygen supply, prompting an increased respiratory rate (hyperventilation), and in turn, expedites the elimination of CO2 from the body, thereby increasing the detrimental effect of alkalosis and impeding the respiratory center's ability to increase respiratory rate to meet oxygen demands.
PARALYSIS OF PHRENIC NERVE
- The phrenic nerve is the sole nerve that innervates the diaphragm with motor function by transmitting signals that control its expansion and contraction, thereby facilitating air inhalation and exhalation by the lungs. If the phrenic nerves are damaged, including paralysis, the diaphragm they innervate ceases to receive nerve impulses, resulting in severe shortness of breath or even cessation of respiration.
SEVERE ANEMIA
- Severe anemia characterizes a condition wherein there is an inadequate supply of oxygen at the tissue level to sustain optimal homeostasis. Hypoxia arises due to insufficient levels of functional hemoglobin in the bloodstream, resulting in a reduction in the transport of O2 to tissue cells.
ADVANCED PREGNANCY
- Advanced pregnancy can inhibit complete diaphragmatic descent, resulting in a tendency for total pulmonary and airway resistances to diminish in late pregnancy as a result of hormonally-induced relaxation of tracheobronchial tree smooth muscles. In advanced pregnancy, hyperventilation occurs due to a decrease in the ventilator recruitment threshold and a rise in central and peripheral chemoreceptor sensitivity induced by the continuous elevations of progesterone and estrogen.
References:
Bhutta, B. S. (2022, August 9). Hypoxia. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK482316/#:~:text=Hypoxia%20is%20a%20state%20in,in%20the%20blood%20(hypoxemia).
Cleveland Clinic. (2022). Phrenic nerve. https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
Lee, S., Chien, D., Huang, C., Shih, S., Lee, W., & Chang, W. (2017). Dyspnea in pregnancy. Taiwanese Journal of Obstetrics & Gynecology, 56(4), 432–436. https://doi.org/10.1016/j.tjog.2017.04.035
LoMauro, A., & Aliverti, A. (2015). Respiratory physiology of pregnancy. Breathe, 11(4), 297–301. https://doi.org/10.1183/20734735.008615
Tortora, G. J., & Derrickson, B. (2017). Principles of ANATOMY & PHYSIOLOGY (15th ed.). Wiley.