Question

You’re on an airplane and the plane begins to shake due to wind turbulence causing you to become nervous and start hyperventilating. How would this hyperventilation affect your body? Draw the pathway, starting with the chemoreceptors, that would depict your body’s response. For review purposes, label the stimulus(i), sensor(s), integrating center(s), effector(s), and physiological response(s).

Answer 1

• Respiratory rate increases in case of high altitude to compensate with the hypoxia of higher altitude, i.e.Hyperventilation.PCo2 decreases 250mm Hg in atmosphere as well as lung alveoli.
• Since normal PCo2 in the lung is 40 mmHg, Now decreased to 25mm Hg, The difference between the deoxygenated blood PCo2 (45 mmHg) is increased . Hence more Co2 is exhaled out to make it in equilibrium.
• Now, PCo2 drops down to 25 mmHg in arterial blood.It affects the brain by crossing blood brain barrier
• Co2 coming to CSF, combines with water in presence of carbonic anhydrase to form carbonic acid which dissociates into bicarbonate and protons(H+)
• These protons act upon the central chemoreceptors, Since the carbonic acid produced is very low in amount, the protons produced is also very less.It is not sufficient to activate the central chemoreceptors.
• Dorsal Respiratory Groups (DRG) present in the medulla of the brain controls the respiratory rhythm by triggering inspiratory impulses.
• Since it is insufficient to generate as much protons that required for the stimulation of DRG, action potential goes down to the phrenic nerve so that to external intercostal muscles.
• Hence the ventilation decreases.Depth of respiration also decreases..Slow breathing.
• So much of Co2 is expired out, causing respiratory alkalosis.
• In a process of increasing the PO2 by hyperventilation, the PCo2 decreases.which inhibit the central chemoreceptors, and hence ventillation is decreased.
• In kidney renal tubules, there is two types of cells 1.intercollated A cells and Intercollated B cells. (which controls acid - base balance.
• In Intrcollated B cells : Co2 + H2O -------------(CARBONIC ANHYDRASE)-------->CARBONIC ACID-------->.HCo2 + H+
• pH of blood increases.Hence kidney pumps out the H+ into blood using ATP to balance the pH.

Physiological responses:

1. light headedness
2. tingling in peripheries
3. visual disturbances

Hyperventilation---------> decreased pCO2--------->RESPIRATORY ALKALOSIS

Respiratory alkalosis causes following physiological changes:

1. O2 decreased to tissue------>paresthesia,fatigue,headache light headedness
2. increased catecholamine release------->increased myocardial contractions-------> coronary ischemia
3. increased intracellular Ca2+ ------------>vascular contraction------------>Increased Blood Pressure