1. Initiation of exercise
> During initiation of exercise, there will obviously be body movement (particularly in the joints and muscles) which will be detected by the sensory receptors called proprioceptors. Proprioceptors will then send nerve impulses to the medulla oblongata which will stimulate its (medulla) inspiratory area, causing our respiratory rate and depth to increase.
2. Moderate exercise
> The same concept explained in the first item may be applied in this scenario. Moreover, during exercise, the muscles expend a lot of energy, which is why there is an increased breathing to allow the lungs to give oxygenated blood to the muscles for them to gain the energy they need.
3. Abrupt ascent into high altitudes
> The peripheral chemoreceptors senses the reduced oxygen levels at high altitudes, which causes hyperventilation (increased respiratory rate) and consequently may cause alkalosis due to increased rate of CO2 removal in the body, inhibiting enhancement of respiratory rate to meet oxygen demands. To compensate, the kidney excretes bicarbonate to allow sufficient respiration without the risk of alkalosis (this process may take days).
4. Paralysis of phrenic nerve
> Paralyzed phrenic nerve will disallow the diaphragm to contract and expand, which consequently also disallow the lungs to inhale and exhale properly. People with paralyzed phrenic nerves will experience decreased respiratory rate and depth, and possibly sleep problems.
5. Severe anemia
> Anemia is a condition that decreases the capacity of the body’s red blood cells to carry oxygen, so there is a decrease in the number of healthy red blood cells in the body. To compensate for this, the lungs will breathe in more air, causing the respiratory rate to increase.
6. Advanced pregnancy
> During pregnancy, there is an elevated level of the hormone progesterone which dilates the smooth muscle of the lungs, causing the mother to breathe in more deeply (increased respiratory depth). The growing uterus during pregnancy also takes up space, putting pressure in the diaphragm which ultimately compresses the lungs, which causes increased respiratory rate to inhale more oxygen.
References:
Badireddy, M., & Baradhi, K. M. (2023, August 7). Chronic Anemia - StatPearls. NCBI. Retrieved October 25, 2023, from https://www.ncbi.nlm.nih.gov/books/NBK534803/
Ben-Joseph, E. P. (2023). Why Do Some Women Feel Short of Breath During Pregnancy? (for Parents) - Nemours KidsHealth. Kids Health. Retrieved October 25, 2023, from https://kidshealth.org/en/parents/breathing.html
Cleveland Clinic. (2022, January 9). Phrenic Nerve: Anatomy & Function. Cleveland Clinic. Retrieved October 25, 2023, from https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
Finlay, J. (2020, February 20). Breathing Changes during Pregnancy — Julia Finlay Osteopath. Julia Finlay Osteopath. Retrieved October 25, 2023, from https://www.juliafinlayosteopath.co.uk/blog/breathing-changes-during-pregnancy
LibreText Medicine. (2023, January 17). 21.11B: Adjustments at High Altitude. Medicine LibreTexts. Retrieved October 25, 2023, from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/21%3A_Respiratory_System/21.11%3A_Respiratory_Adjustments/21.11B%3A_Adjustments_at_High_Altitude
Tortora, G. J., & Derrickson, B. H. (2016). Principles of Anatomy and Physiology. Wiley.