Chapter 6

Respiration

The three components of the respiratory system

• External respiration

• Gas transport

• Internal respiration

The three functions of the respiratory system

• External respiration or pulmonary ventilation

• Gas transport and distribution from the lungs to the tissues via the blood

• Internal or tissue respiration

Sequence of air flow in external respiration1. Through nose2. Into nasal cavity3. Past turbinates4. Through nasopharynx5. Past the glottis6. Into trachea7. To bronchi8. To lungs9. To smaller bronchi10. To bronchioles11. To terminal bronchioles12. To respirator bronchioles13. Alveolar ducts14. Alveoli

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The respiratory system, showing the respiratory passages and the function of the alveolus to oxygenate the blood and to remove carbon dioxide.

The respiratory cycle

• Inspiration phase– Active phase

• Expiration phase– Passive phase

Mechanics of lung ventilation

• Inspiration– The diaphragm descends and the external and

anterior internal intercostal muscles raise the ribs– Volume of lungs increases– Lowers pressure within the lungs (creates a

pressure gradient)– Air moves into the lungs

• Expiration– The diaphragm and intercostals recoil to their

resting length– Recoil creates a higher-than-atmosphere pressure

in the lungs– Pressure gradient moves air out of the lungs

Diagram of inspiration and expiration

Lung ventilation during exercise

• Scalene and sternocleidomastoid muscles help lift ribs in inspiration

• Abdominal muscles aid in expiration• Raise intra-abdominal pressure• Draw lower ribs downward and medially

The four primary lung volumes

• Tidal volume

• Inspiratory reserve volume

• Expiratory reserve volume

• Residual volume

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Lung capacities

• Total lung capacity

• Vital capacity

• Inspiratory capacity

• Functional residual capacity

Respiratory control

Input to respiratory center comes from

• Neural input within the brain

• Neural input from muscles and joints

• Humoral input

Breathing patterns during exercise

• Rate and depth

• Type of exercise

• Diaphragmatic versus costal breathing

• Oral versus nasal breathing

The ventilation equivalent

• The number of liters of air breathed for every 100 ml of oxygen consumed.

• At rest, approximately 25.4 liters of air must be inspired for a person to consume 1 liter of oxygen.

Respiratory phenomena

• Stitch in the side– Perhaps caused by ischemia of the

diaphragm or intercostal muscles

• Second wind– Occurs when body makes metabolic

adjustments to exercise

• Exercise-induced asthma (EIA)– Swimming well tolerated by asthmatics– Continuous running most likely to trigger

Respiratory phenomena (cont.)

• Hypoventilation– Typical of airway obstruction– Metabolism occurring at faster rate than

lung ventilation

• Hyperventilation– Lung ventilation rate is greater than

metabolism– Decreasing quantities of CO2 (hypocapnia)– Used by swimmers

Training and pulmonary function

• Endurance training– Decreases functional residual capacity– Decreases residual volume– Decreases ratio of residual volume/total lung

capacity– Increases vital capacity

• Respiratory muscle fatigue– Lack of sufficient blood flow to provide

adequate oxygen and remove metabolic byproducts

– Limits exercise performance

Effects of exposure to ozone on athletic performance

• Decreases distance running ability

• Reduces VO2 max

• Decreases maximum ventilation rate• Causes shallow rapid breathing during

submaximal exercise as well as a reduction in tidal volume

Effect of endurance training on respiration

• Makes breathing more efficient• Reduces metabolic acidosis• Increases oxidative capacity of the respiratory

muscles• Decreases functional residual capacity• Decreases residual volume• Decreases the ratio of residual volume/total

lung capacity• Increases vital capacity

Gas transport

Three processes occur between lung

ventilation and tissue respiration:

1. Diffusion of oxygen across the wall of the alveolus and the wall of the capillary

2. Transport of oxygen in the blood to the capillary bed of the muscles

3. Diffusion of oxygen across the capillary wall to the active muscle fibers

Percentage and partial pressures of O2 by altitude.

Some basic properties of gases

• Composed of molecules that are in constant motion at high velocities

• Have no definite shape or volume, but conform to that of the container

• Pressure results from the constant impact of molecules on the wall of the container

• Pressure can be increased by confining gas to a smaller volume or increasing the activity of the molecules

• Heat increases the molecular velocity, which increases pressure

Composition of respiratory gases

• Atmospheric air composed mainly of– nitrogen, – oxygen, – and carbon dioxide

Diffusion gradients

for oxygen

60 mm Hg

for carbon dioxide

5 to 6 mm Hg

Gas transport by the blood

• Oxygen– Blood transports 20 volume percent of oxygen,

100 times a much as will dissolve in solution

– Hemoglobin binds with oxygen

• Carbon dioxide1. Diffuses across cell membrane into the tissue

fluid then across capillary wall into blood plasma

2. Most diffuses from plasma into red blood cell

3. Red blood cells transport the carbon dioxide

Oxygen dissociation curve

• Amount of oxygen released from hemoglobin as a result of changing carbon dioxide levels in the tissues

• Curve is steep when the partial pressure of oxygen is low

The oxygen dissociation curve for human blood

The coefficient of oxygen utilization during exercise

• The proportion of oxygen transported by the blood that is given off to the tissues– During resting conditions– During exercise

The two processes involved in the control of acid-base balance

• Buffer systems– Carbonic acid bicarbonate system

– Blood proteins

– Hemoglobin and oxyhemoglobin

• Physiological changes– In respiratory function

– In kidney function

The acid-base balance limits performance because

• When exercise intensity increases beyond aerobic capacity, lactic acid becomes the end product of metabolism

• The body’s ability to buffer lactic acid plays a large role in determining the end point of anaerobic activity

Effect of exercise on lung diffusion

The diffusion of oxygen from the alveoli to thepulmonary capillaries increases in directproportion to the intensity of the exercise

Breathing oxygen-enriched gas before or after exercise to improve performance or aid recovery

• Not useful physiologically• May have a psychological effect if the

athlete believes the oxygen helps.

Limits on the maximal oxygen consumption rate (VO2 max)

• During activities involving large muscle groups:– Cardiac output

• During activities that involve only arms or only legs:– Muscular blood flow

– Oxygen utilization