1. Respiratory center in brain stimulates phrenic and intercostal nerves 2. Nerves send impulses to resp muscles 3. IM and D contract 4. Thoracic cav V incr 5. Lungs expand so intrapleural and intrapulmonary P decreases 6. Air sucked in lungs (inhale) 7. Muscles relax, air out of lungs (exhale)

Lecture 17 Flashcards by Zoé Lauzé

3 basic steps of respiration

Pulmonary ventilation
External ventilation
Internal ventilation

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What is pulmonary ventilation/breathing (inhalation/exhalation)

Exchange of air bet atmosphere and alveoli of lungs

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What is external (pulmonary) respiratory

Exchange of gases between air in alveoli and blood in capillaries across respiratory membrane

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What is internal (tissue) respiration

Exchange of gases between blood in systemic capillaries and tissue cells

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How does flow of air between atmosphere and lungs occur

Difference in air pressure (high to low)

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When diaphragm is relaxed, what is the diff between alveolar air pressure and atm pressure

0, both at 760mmHg

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During inhalation, pressure in lung decr or incr

Decrease (more space, same amount of gas)

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Bc during inhalation pressure lowers in lungs, air moves

Into lungs

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When diaphragm contracts (inhalation), alveolar pressure drops to

757 mmHg

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Body parts during inhalation

Thoracic cavity expands, external intercostal muscles and diaphragm contract

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Why does contraction of diaphragm increases thoracic cavity

Bc it flattens and lowers the dome -> more space for lungs

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When intercostal muscles contract,

Elevates ribs

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Why is inhalation said to be an active process

Bc involves muscular contraction

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Why is exhalation not a passive process

Bc no muscular contraction

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What results from elastic recoil of chest wall and lungs

Exhalation

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Body mvmt during exhalation

External IM relax, diaphragm relaxes, ribs are depressed

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When exhalation decreases thoracic cavity, pressure in lungs increases to

763 mmHg

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During exhalation, atm 760 and lungs 763 so air

Flows out

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Ventilation steps

Respiratory center in brain stimulates phrenic and intercostal nerves
Nerves send impulses to resp muscles
IM and D contract
Thoracic cav V incr
Lungs expand so intrapleural and intrapulmonary P decreases
Air sucked in lungs (inhale)
Muscles relax, air out of lungs (exhale)

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Negative pressure and positive pressure mean

Negative: lower than atm P
Positive: higher than atm P

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Atm pressure at sea level (normal atm P)

760 mmHg

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Intrapulmonary/intra alveolar P is

P of air within alveoli (equalizes atm bet breaths but doesn’t stay there)

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Intrapleural P

P within pleural cav, changes at diff phases of breathing, ALWAYS 4 mmHg LESS than intrapulmonary P

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If intrapleural P wasn’t negative to lungs, they would

Collapse bc air would flow to low P

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At rest, three P are at

Atm: 760 Intra alveolar: 760 Intrapleural: 756

Lungs tend to get pulled inward bc of the

Recoil of elastic tissue in them

As lungs move away from thoracic wall, cav gets larger so

Negative P in cav suctions lungs to stay inflated and not collapse

What is trans pulmonary P

P difference between inside of lungs (intra alveolar) and outside of lungs (intrapleural)

Trans pulmonary P needs to stay how to keep lungs inflated

Positive (lungs - cav, 760 - 756)

Ventilation depends on 3 types of P:

Atm Intrapulmonary Intrapleural

3 types of P when inhaling

Atm: 760 Intra alveolar: 758 Intrapleural: 754

3 types of P when exhalation

Atm: 760 Intra alveolar: 762 Intrapleural: 758

Tidal volume

Amount of air moving in/out of lungs each breaths (500ml)

Inspiratory reserve volume (IRV)

Amount of air that can be forcibly inspired beyond tidal volume (2100-3000ml)

Expiratory reserve volume (ERV)

Amount of air can be forcibly expelled after normal TV inhalation (1000-1200ml)

Residual volume (RV)

Amount of air remaining in lungs even after max exhalation (after max, still 1200 ml left to help prevent collapse of alveoli)

Vital capacity

Total amount of exchangeable air (IRV + TV + ERV)

Total lung capacity

Sum all lung volume (IRV + ERV + TV + RV)

Apparatus used to measure air exchange volume when breathing is

Spirometer

Airway resistance

Resistance of respiratory tract to airflow during inhalation and exhaustion

Airway resistance is mainly related to

Diameter of airways

When airway resistance rises

Breathing mvmts become more strenuous

Alveolar surface tension

Amount of H bonds in liquid coating alveoli

Water mainly coats alveoli walls so without surfactant, which breaks H bonds,

Alveoli would collapse (surfactant reduces surface tension)

What is lung compliance

Ability to expand lungs

Factors affecting lung compliance

Surface tension and elasticity from elastin in connective tissue, smoking, emphysema, obesity and pregnancy (reduce volume of chest)

Scar tissue caused by infections or low surfactant production decreases lung compliance bc

Elastin fibres in lungs are replaced by collagen which is less elastic

Major determinants of airway resistance

Radii of airways

Airway resistance determines

How much air flows in lungs at any P diff bet atm and alveoli

Lung compliance is determined by

Elastic connective tissues of lungs and surface tension of fluid lining alveoli

Factors that can affect ventilation

Airway resistance, lung compliance, alveolar surface tension and scar tissue

Walls of airways, especially ___ offer some resistance to airflow

Bronchioles

Asthma

Chronic, bronchial tubes inflame and narrow -> hard to breathe

Asthma is caused by

Genetic and eviro factors

Asthma symptoms

Wheezing, coughing, chest tightness, SOB

Chronic obstructive pulmonary disease (COPD)

Group of diseases that cause airflow blockage

Chronic bronchitis (COPD disease)

Irritates bronchial tubes -> swell and mucus builds up -> cilia damaged by disease so can't help clear mucus

Result of emphysema

Reduced surface for gas exchange or o2/co2 bet inhaled air and blood traversing lungs

Emphysema characterized by

Destruction of gas exchanging tissue -> large air space bc loss of alveolar walls are destruction of capillaries

Emphysema (COPD) most commonly caused by

Smoking

Cystic fibrosis (genetic disease)

Buildup of thicker and stickier mucus -> bacteria gets more frequently stuck so frequent infections

Average lifespan for cystic fibrosis

37 yo, death generally from heart failure bc massive chronic bacterial infection to lung

Pneumothorax (collapsed lung)

Air enters pleural cav-> pressure not - to intrapulmonary, so lung collapses (Getting air out of pleural cav can reinflate lung)

Atelectasis

Collapsed of one/more parts of lung specifically alveoli sacs -> alveoli can't fill o2 so this lung area doesn't function

Compressive atelectasis

Something (fluid/air/blood/tumor) around lung pushes it -> collapses

Obstructive atelectasis

No new air can move in alveoli (airflow obstruction)

Contraction atelectasis

Lung scarring