Respiratory Physiology (Day 1) Flashcards

Question

Lung compliance

Answer 1

Lungs expand when stretched. Defined as change in lung volume per change in transpulmonary pressure: ΔV/ΔP Index of the ease with which the lungs expand under pressure—> high compliance: easily stretched --> low compliance: requires more force, restrictive lung diseases (e.g. pulmonary fibrosis, surfactant deficiency)

Answer 2

Return to initial size after being stretched (recoil) Lungs have elastin fibers. Because the lungs are stuck to the thoracic wall, they are always under elastic tension. Tension increases during inspiration and is reduced by elastic recoil during expiration.

Answer 3

"force holding fluid molecules together in an air-fluid interface... due to strong attractive force of H bonds between H2O molecules" Resists distension, promotes collapse of alveolar space Exerted by fluid secreted on the alveoli Fluid is absorbed by active transport of Na+ and secreted by active transport of Cl- --> any imbalance between these can result in viscous fluid that is difficult to clear --> raises the pressure of the alveolar air as it acts to collapse the alveolus Ex. People with cystic fibrosis have a genetic defect that causes such an imbalance of fluid absorption and secretion

Answer 4

Pressure is DIRECTLY proportional to surface tension and INVERSELY proportional to radius of alveolus. Small alveoli would be at greater risk of collapse without surfactant.

Answer 5

SURFACE ACTIVE AGENT Secreted by type II alveolar cells Consists of hydrophobic protein and phospholipids REDUCES surface tension between water molecules by reducing the number of hydrogen bonds between water molecules More concentrated as alveoli get smaller during expiration to equalize pressure. Prevents collapse Allows a residual volume of air to remain in lungs

Answer 6

Production of surfactant begins late in fetal life, so premature babies have higher risk for alveolar collapse--respiratory distress syndrome (RDS) --> treated with surfactant Similar problem may occur in adults with septic shock --↓ lung compliance, ↓ surfactant—acute respiratory distress syndrome (ARDS); NOT treatable with surfactant

Answer 7

used for forced inspiration

Answer 8

raises rib cage during inspiration

Answer 9

works w/external intercostals

Answer 10

contracts in inspiration - lowers --> enlarging thoracic cavity relaxes in expiration - raises --> thoracic cavity smaller

Answer 11

lowers rib cage during forced expiration

Answer 12

abdoominal muscles are also used in forced expiration

Answer 13

occurs with the relaxation of the inspiratory muscles (PASSIVE)

Answer 14

Volume of thoracic cavity (and lungs) increases vertically when diaphragm contracts (flattens) and laterally when parasternal and external intercostals raise the ribs. --Thoracic & lung volume increase --> intrapulmonary pressure decreases --> air in --occurs when alveolar pressure decreases 1. thoracic cage expands outwards 2. diaphragm drops down- contracts and flattens - -> both of these lead to increased thoracic volume and decreased thoracic (alveolar) pressure

Answer 15

Volume of thoracic cavity (and lungs) decreases vertically when diaphragm relaxes (dome) and laterally when external and parasternal intercostals relax for quiet expiration or internal intercostals contract in forced expiration to lower the ribs. --Thoracic & lung volume decrease --> intrapulmonary pressure increases --> air out

Answer 16

Unlike cardiac muscle, skeletal muscles are NOT spontaneously active, so they must be stimulated by nerve signals. Rhythmic pattern of contraction & relaxation of breathing muscles arises from a neural network of spontaneously discharging motor neurons from: 1. CEREBRAL CORTEX (voluntary breathing) 2. MEDULLA OBLONGATA and PONS (Involuntary breathing) Motor neurons-- innervate diaphragm/other breathing muscles; regulated by descending neurons from the brainstem (Medulla & Pons).

Answer 17

Two rhythmicity centers: excitatory inspiratory neurons vs neurons which inhibit those inspiratory neurons—intrinsic rhythmicity, but influenced by other factors. 1) Involuntary breathing (e.g. at rest) - intrinsic to medulla 2) Voluntary (“forced,” e.g. exercise) - input from cerebral cortex

Answer 18

Two resp control centers: 1) apneustic (stimulates inspiratory neurons in medulla) 2) pneumotaxic (antagonizes apneustic to inhibit inspiration)