The Respiratory System and Its Regulation

1. chapter 6 The Respiratory System and Its Regulation

2. Anatomy of the Respiratory System

3. Transportation of Oxygen and Carbon Dioxide • Pulmonary ventilation (breathing): movement of air into and out of the lungs Air is drawn in the lungs via the nose and the mouth. It is drawn in via the mouth when the demand for air exceeds what the nose can bring in. From the nose and mouth the air travels through the pharynx-larnyx-trachea-and into the left and right bronchi-bronchioles-alveoli Gas exchange occurs in the alveoli. This is known as the respiratory zone.

4. Boyle’s Law • The pressure within the lungs is less than the pressure outside of the body. • Because the respiratory tract is open to the outside, air (oxygen) rushes into the lungs during inspiration.

5. Pulmonary Ventilation Inspiration: active process involving the diaphragm (flattens out) and the external intercostal muscles (move ribs and sternum out of the way. Pressure in the lung is less than the air pressure outside the body, air following the pressure gradient coming into the lung Expiration: usuallya passive process involving relaxation of the inspiratory muscles; pressure increases in the lungs and air is forced out Active process during forced breathing

6. Pulmonary Diffusion • Gas exchange in the lungs • Replenishes blood's oxygen supply that has been depleted for oxidative energy production • Removes carbon dioxide from returning venous blood

7. Pulmonary Volumes • Tidal Volume: Amount of air leaving and entering lungs with each breath • Vital Capacity: The greatest amount of air that can be expired after a maximal inspiration • Residual Volume: Amount of air left in the lungs after a maximal expiration’ • Total Lung Capacity: The sum of vital capacity and residual volume.

8. Blood Flow to the Lungs at Rest • At rest the lungs receive approximately 4 to 6 L/min of blood flow, depending on body size.

9. Respiratory Membrane: Gas Exchange • Gas exchange between the air in the alveoli and the blood in the pulmonary capillaries occurs across the respiratory membrane. This membrane consists of the: Alveolar wall Capillary wall Basement membranes (0.5-4.0 microns thick) • Gases will move along a concentration gradient based on partial pressures • The air we breath is composed of 79.04% Nitrogen, 20.93% oxygen and 0.03% carbon dioxide.

10. Anatomy of the Respiratory Membrane

11. Gas Exchange Cont. • If the pressure on each side of the membrane is equal, the gases would be in equilibrium and would not move. • When the deoxygenated blood goes into the lungs for oxygen the pressure within the capillaries is lower than in the alveoli therefore, the oxygen will move from the alveoli into the capillaries to be transported back to the heart.

12. Oxygen Transport • Oxygen is transported bound to hemoglobin (protein) (>98%) or dissolved in plasma (<2%) • Hemoglobin concentration largely determines the oxygen-carrying capacity of blood • 1 liter of plasma= 3mL of oxygen (a total of 3-5L of blood plasma in the body for a total of 9-15 mL of Oxygen • A resting body needs at least 250 mL of oxygen per minute • Hemoglobin contains approximately 4-6 billion red blood cells allowing blood to transport nearly 70 times more oxygen than can be dissolved in plasma. • Oxygen carrying capacity seldom limits performance in healthy individuals

13. Blood Oxygen-Carrying Capacity • Each 100mL of blood contains an average of 14 to 18g of hemoglobin (protein that transports oxygen) in men and 12-16g in women. (1 L = 1,000 mL) • Each gram of hemoglobin can combine with 1.34 mL of oxygen, so the oxygen carrying capacity of blood is approximately 16-24 mL per 100 mL of blood. • When fully saturated with oxygen a man (5 L of blood) will have approximately 188 mL to 241 mL of oxygen. • During rest, the blood passes through the lungs and is in contact with the alveoli for .75 seconds, enough time to become 98-99% saturated with oxygen • At high intensities the contact time is reduced and the saturation of oxygen is slightly reduced.

14. Carbon Dioxide Transport • Bicarbonate ions: Bicarbonate ions (released by hemoglobin) maintain the pH balance by offsetting the hydrogen ions (H+) that are the result of carbon dioxide in the blood. Accounts for 60-70% transportation of carbon dioxide in the blood • Dissolved in blood plasma: 7-10% of carbon dioxide is transported this way. • Bound to hemoglobin (carbaminohemoglobin) 20-30% of carbon dioxide is transported in this manner.

15. Gas Exchange at the Muscles: Arterial–Venous Oxygen Difference

16. A-Vo2 Difference • The amount of oxygen in the arterial blood as opposed to the amount of oxygen in the venous blood. • The blood is less in the venous blood because it has be delivered to the cells of the body.

17. Oxygen Transport in the Muscle • Oxygen is transported in the muscle to the mitochondria by a molecule called myoglobin. • Gives the muscle a red colored appearance

18. Factors Affecting Oxygen Uptake and Delivery 1. Oxygen content of blood: Under normal conditions, hemoglobin is about 98% saturated with oxygen 2. Amount of blood flow: Increased blood flow increases oxygen delivery however, it also has to make up for the diminished amount of oxygen in the blood. 3. Local conditions within the muscle: Increase in physical stress means increase in muscle temp, which means increase in oxygen delivery. Increase in muscle activity also means increase in lactate production which improves oxygen delivery.

19. Regulation of Pulmonary Ventilation • Higher brain centers • Expiratory centers • Inspiratory centers • Chemoreceptors • Mechanoreceptors in the active muscles and the lung muscles • Hypothalamic input • Conscious control