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1,000

2,000

3,000

4,000

5,000

6,000

Mil

lili

ters

(m

l)

Inspiratoryreserve volume3,100 ml

Tidal volume 500 mlExpiratoryreserve volume1,200 ml

Residual volume1,200 ml

Vitalcapacity4,800 ml Total lung

capacity6,000 ml

Tidal Volume (TV): total air moved with each breath Normal breathing moves about 500 ml

Inspiratory reserve volume (IRV): Amount of air that can be taken in forcibly over the tidal volume

Usually around 3,100 ml

Expiratory reserve volume (ERV):

Amount of air that can be forcibly exhaled after a tidal expiration Approximately 1,200 ml

Residual volume: Air remaining in lung after expiration (about 1,200 ml) Allows gas exchange between breaths; keeps alveoli inflated

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Vital capacity (VC): The total amount of exchangeable air Vital capacity = TV + IRV + ERV

Avg. 4,800 ml in men; 3,100 ml in women

Dead space volume: about 150 ml Air remaining in resp. tract; never reaches alveoli

Functional volume: about 350 ml Air that actually reaches the respiratory zone

(bronchioles/alveoli)

spirometer –measures respiratory capacities

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caused by reflexes or voluntary actions

Cough and sneeze —clears lungs of debris Crying/laughing —emotionally induced

mechanism Hiccup —sudden inspirations

Spasms/irritation of diaphragm or nerve Yawn —very deep inspiration

Thought to cool CSF/brain blood

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Soft murmurs like a muffled breeze Monitored with a stethoscope

Bronchial sounds –air through large passageways trachea/bronchi

Vesicular breathing sounds - alveoli filling with air

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Oxygen: ◦ Most attaches to hemoglobin to form oxyhemoglobin (HbO2)

◦ small dissolved amount is carried in the plasma

Carbon dioxide: ◦ Most transported in plasma as bicarbonate ion (HCO3

–)

◦ eventually released into RBC to form carbonic acid (H2CO3) splits to release CO2

◦ Small amount carried in RBC bound to hemoglobin (at different sites than oxygen)

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CO2O2

Hb + O2 HbO2 HCO3−+ H+ H2CO3 CO2+ H2O

(a) External respiration in the lungs(pulmonary gas exchange)

Oxygen is loaded into the bloodand carbon dioxide is unloaded.

Alveoli (air sacs)

Loadingof O2 Unloading

of CO2

(Oxyhemoglobinis formed)

Bicar-bonateion

Carbonicacid

Water

Plasma

Red blood cell

Pulmonary capillary

CO2 +H2O H2CO3 H++ HCO3−

HbO2 Hb + O2

CO2 O2

(b) Internal respiration in the body tissues(systemic capillary gas exchange)

Oxygen is unloaded and carbondioxide is loaded into the blood.

Plasma

Systemic capillary

Red blood cell

Loadingof CO2

Unloadingof O2

Tissue cells

Water Carbonicacid

Bicar-bonateion

Nerves: the phrenic and intercostal nerves◦ Control diaphragm and external intercostals

Medulla: ◦ Sets breathing rate and depth of breathing◦ Controls overinflation of alveoli

Stretch receptors in alveoli too◦ contains a pacemaker (self-exciting inspiratory

center) called the ventral respiratory group (VRG)

Pons—coordinates/smooths respiratory rate

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Breathing control centers:• Pons centers• Medulla centers

Afferentimpulses tomedulla

Breathing control centersstimulated by:

CO2 increase in blood(acts directly on medullacenters by causing adrop in pH of CSF)

Nerve impulsefrom O2 sensorindicating O2

decrease

CSF inbrainsinus

O2 sensorin aortic bodyof aortic arch

Intercostalmuscles

Diaphragm

Efferent nerve impulses frommedulla trigger contractionof inspiratory muscles.• Phrenic nerves• Intercostal nerves

• Physical factors/Emotional Factors– Increased body temperature/Exercise– Talking/Coughing– Fear, anger, excitement

• Conscious control): holding your breath• Respiratory centers override this when oxygen

gets too low and pH drops

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• Chemical :– Increased levels of carbon dioxide causes:• decreased or acidic pH of CSF• an increase in rate and depth of breathing

• The body’s need to rid itself of CO2 is the most important stimulus for breathing• Acts directly on the medulla oblongata

• Changes in Oxygen are monitored by chemoreceptors in the aorta and carotid

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