Respiratory Physiology

Question 1

what parts of ventilation are active and which are passive?

Answer 1

• inspiration: active (muscles contract)
• expiration: passive (muscles relax) unless under stress

Question 2

TV

Answer 2

Tidal volume
air that moves into the lung with each quiet inspiration

normal ~500 mL

Question 3

RV

Answer 3

residual volume
air in lung after MAX expiration

cannot be measured by spirometry

Question 4

IRV

Answer 4

inspiratory reserve volume

air that can still be inhaled after normal inspiration

Question 5

ERV

Answer 5

expiratory reserve volume

air that can still be exhaled after normal expiration

Question 6

IC

Answer 6

inspiratory capacity
IRV + TV

air that can be inhaled after normal exhalation

Question 7

FRC

Answer 7

functional residual capacity
RV + ERV

vol of gas in lungs after normal expiration

cant measure w spirometry bc includes RV

Question 8

VC

Answer 8

vital capacity
IRV + TV + ERV

max vol of gas that can be expired after max inspiration

Question 9

TLC

Answer 9

total lung capacity

volume of gas present in lungs after max inspiration

Question 10

minute ventilation

Answer 10

total vol of gas entering the lungs per min

= TV x RR

Question 11

alveolar ventilation

Answer 11

vol of gas that reaches alveoli each min

(TV-phys dead space) x RR

Question 12

what is physiologic dead space (VD)

Answer 12

anatomic dead space + alveolar/functional dead space (usually = anatomic dead space)

dead space = no gas exchange, no pulmonary blood flow

Question 13

elastic recoil

Answer 13

• the lungs intrinsic nature to deflate with expiration
• tendency for lungs to collapse in and chest wall to spring out at physiologic baseline (opp motions balance and prevent lung collapse)

Question 14

pulmonary pressures at FRC

Answer 14

• airway and alveolar pressures equal atmospheric pressure (zero)
• intrapleural pressure is neg

Question 15

compliance def and factors that affect it

Answer 15

change in lung vol for a change in pressure; inc compliance = lung easier to fill

inversely proportional to wall stiffness (inc compliance, dec stiffness)

inc by surfactant

Question 16

how does CO2 get to the lungs?

Answer 16

CO2 enters RBC from tissue and is convertred into 3 forms where it is transported to the lungs, from most to least:
- converted into bicarb (via carbonic anhydrase; bicarb/chloride transport on RBC membrane)
- carbamino hemaglobin (bound to deoxy N-terminus, not heme)
- dissolved in plasma

Question 17

what triggers the release of CO2?

Answer 17

oxygenation of hemoglobin promotes dissociation of H from hemoglobin >

shifts equilibrium toward CO2 formation >

releases CO2 from RBCs (haldane effect)

Question 18

pulmonary circulation

Answer 18

• low resistance, high compliance system
• oxygen diffuses slowly across alveolar membrane
• carbon dioxide diffuses rapidly

Question 19

pulmonary diffusion increases with:

Answer 19

• increased area
• larger difference between partial pressures

Question 20

pulmonary diffusion decreases with:

Answer 20

• decreased area
• less difference between partial pressures
• thicker alveolar wall

Question 21

pulmonary vascular resistance decreases with:

Answer 21

• inc CO
• inc vessel radius (vasodilation)
• dec arterial pressure
• dec blood viscosity
• dec vessel length
• alkalosis
• anemia

Question 22

pulmonary vascular resistance equation

Answer 22

pul artery pressure - pul artery occlusion pressure

/

CO

Question 23

pulmonary vascular resistance increases with:

Answer 23

• acidosis
• hypoxia
• hypothermia
• sympathetic stim

Question 24

V/Q ratio in various lung zones and common associated conditions

Answer 24

ventilation perfusion ratio

Zone 1 (apex of lung): V/Q ratio INC
- ventilation dec, but perfusion dec more
- TB

Zone 2 (middle): V/Q = 1

Zone 3 (base): V/Q ratio DEC
- ventilation inc, but perfusion inc more
- immune conditions, COPD

Question 25

what are the main components of alveolar gas exchange?

Answer 25

• SA
• PP gradients of gases
• matching of ventilation and perfusion

Question 26

what are some of the controls of ventilation and perfusion?

Answer 26

• central chemoreceptors
• cerebral cortex
• pontine respiratory centers
• peripheral chemoreceptors
• pulmonary inputs (stretch, irritant, J receptors)

all > medullary respiratory centers > lung movement

Question 27

how is CO2 and O2 status in the body measured?

Answer 27

• chemoreceptors on the surface of the medulla detect pH changes in the CSF
• peripheral chemoreceptors (on carotid and aortic bodies) detect pH/Co2/O2 changes in blood and transmit signal via vagus and glossopharyngeal nerves

Question 28

CNS and ventilation control

Answer 28

• signals sent from chemoreceptors fed to respiratory center in brain stem where there are inspiratory and expiratory neurons (expiratory for deep expiration only)

medulla has three respiratory control centers:
- dorsal resp group (inspiration)
- ventral resp group (expiration)
- pre-botzinger complex (intrinsic rhythm generator)

they interact w pons at pneumotaxic center and apneustic center (inhibits or stim inspiration)

Question 29

mechanoreceptors in the lungs

Answer 29

assess mechanical status of lungs via vagus nerve

stretch receptors activated when lungs excessively inflated
- triggers inspiration reflex; stops inspiration and prolongs expiration

fibers synapse in cervical and thoracic spine and synapse with motor neurons
- phrenic nerves: diaphragm
- intercostal nerves: intercostal muscles

Question 30

pain, emotion, and voluntary control

Answer 30

• limbic and hypothalamus send info to respiratory center
• voluntary control from primary motor cortex > communicates directly to spinal cord, bypassing info from brainstem