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Home , Minute ventilation

The - 7 Regulation of

Jennifer Carbrey Ph.D. Department of Cell Biology image by OCAL, http://www.clker.com/clipart-26501.html, public domain Respiratory System

1. Anatomy and mechanics 2. volumes and compliance 3. Pressure changes and resistance 4. Pulmonary function tests and alveolar ventilation 5. Oxygen transport

6. CO2 transport and V/Q mismatch 7. Regulation of breathing 8. Exercise and Reflex Loop Regulates Breathing

Peripheral carotid receptors and aortic bodies

stimulated by: decrease in PaO2 (hypoxia) increase in PaCO2 (respiratory acidosis) decrease in pH within the arterial blood (metabolic acidosis)

Central throughout the brain stem

sense H+ but influenced by arterial PCO2 since CO2 but not H+ crosses blood-brain barrier Inspiratory Receptors of the Lung

1. Pulmonary stretch receptors located in the smooth muscle of the large and small airways of the lung are mechanoreceptors that fire with the inflation of the lung. These receptors stop inspiration as part of the Hering- Breuer reflex. In the adult this reflex is evoked only under conditions of large tidal volumes as in rigorous exercise.

2. J Receptors located in the walls of the pulmonary capillaries which are stimulated by pulmonary vascular congestion, edema, air emboli (air in the blood), and low . Stimulation of these receptors can result in rapid breathing (), and or labored breathing (dyspnea).

3. Pulmonary irritant receptors located in airway epithelium and the nasal mucosa. Mechanical or chemical irritation elicits a cough reflex and . Transport of H+ & pH H+ binding to

HbO2

O2 O2 Hb

CO2 HbH CO2 + H2O H+

HCO3- tissues

- + H2O + CO2 = H2CO3 = HCO3 + H Effects of PaO2 and PaCO2

PaCO2

PaO2

80 mmHg

ventilation minute minute ventilation minute

100 mmHg 40 mmHg PaO2 PaCO2 c.a. H+ + HCO3- = H2CO3 = H2O + CO2

Effects of plasma [H+]

Minute ventilation Minute 7.4 7.33 plasma pH

plasma [H+] pH PaCO2 ventilation Respiratory acidosis increased decreased increased (>45 mmHg) decreased ventilation is the cause Respiratory alkalosis decreased increased decreased (<35 mmHg) increased ventilation is the cause Metabolic acidosis increased decreased decreased increased ventilation is the compensation Metabolic alkalosis decreased increased increased decreased ventilation is the compensation Key Concepts

Respiratory acidosis and alkalosis result from increases and decreases, respectively in PaCO2 levels. Metabolic acidosis and alkalosis are conditions in which changes in PaCO2 are not the primary cause for changes in pH.

At rest, arterial PCO2 is the most important determinant in the ventilatory drive.

The detect changes in arterial PCO2 by sensing H+ concentration in interstitial tissue. Peripheral chemoreceptors (carotid bodies) sense changes in arterial PO2, PCO2, and H+ levels (pH). Low plasma pH always increases minute ventilation.