respiratory physiology

Question 1

what are the 3 processes in exchange of air

Answer 1

1. pulmonary ventilation
   -inspiration
   -expiration
2. external respiration
   3, internal respiration

Question 2

pulmonary ventilation

Answer 2

the result of pressure gradients caused by changes in thoracic cavity volume
-boyles law
gas volume is inversely proportional to pressure

Question 3

what pressures are involved in pulmonary ventilation

Answer 3

a. atmospheric pressure
b. intrapulmonary pressure
c. intrapleural pressure

Question 4

what are the processes of pulmonary ventilation

Answer 4

a. quiet inspiration
- active process
at start Patm =P pul, no air moves in
b. forced inspiration
-active process
- diaphragm, external intercostals + sternocledomastoid
- increase volume of thoracic cavity
c. quiet expiration
-relax diaphragm, ext. intercostal
d. forced expiration
- laboured breathing
- relax diaphragm, ext.. intercostals +contract internal intercostals

Question 5

what happens after no air moves in from Patm=Ppul

Answer 5

a. diaphragm contract, increase volume of thoracic cavity
b. lungs resist expansion
c. higher pressure difference between Ppul and Pip pushes lungs out
d. air moves down P gradient

Question 6

stretch in lungs is determined by:

Answer 6

compliance: effort needed to stretch lungs
recoil: ability to return to resting size after stretch

Question 7

lungs collapsing is prevented by

Answer 7

a. Pip is always below Ppul

b. presence of surfactant

Question 8

respiratory distress syndrome

Answer 8

• newborns < months gestation

- inadequate surfactant

Question 9

lipoprotein/phospholipid mixture

Answer 9

• in watery film coating alveoli

- allows easier stretch of lungs

Question 10

F=(triangle)(P)/ R

Answer 10

f=air flow
(triangle)(P) = Patm - Ppul
R=airway resistance

Question 11

how is resistance determined

Answer 11

by diameter of bronchi, bronchioles

Question 12

how is airway resistance effected

Answer 12

asthma, bronchitis and emphysema increase airway resistance making it more difficult to expire than to inspire

Question 13

what opens and closes the airways

Answer 13

inspiratory mechanics open airways

expiratory close airways

Question 14

how are respiratory volumes measured

Answer 14

a spirometer

-1 respiration = 1 inspiration + 1 expiration

Question 15

what are the different volumes in respiratory volumes

Answer 15

1. tidal volume - inspired or expired air during quiet respiration
2. inspiratory reserve volume - excess air over TV takin in on a max inspiration (~ 3000 ml)
3. expriatory reserve volume - excess air over TV push out on max expiration (~1200 ml)
4. residual volume - volume of air in lungs after maximal expiration
5. minute respiratory volume = TV X respiratory rate
6. forced expiratory volume in 1 second : volume expires in 1 second with max effort, following mac inspiration

Question 16

lung capacities

Answer 16

2 or more volumes

Question 17

inspiratory capacity

Answer 17

TV+IRV

Question 18

vital capacity

Answer 18

TV+IRV+ERV

Question 19

total lung capacity

Answer 19

max amount of air lungs can hold

Question 20

clinical applications

Answer 20

FEV1 is measured while measuring VC +expressed

Question 21

obstructive disorders

Answer 21

involve emphysema, asthma, cystic fibrosis

- hard to expire = increase resistance

Question 22

restrictive disorder

Answer 22

scoliosis, pneumothorax

• restrict lung expansion
• hard to inspire

Question 23

external respiration

Answer 23

O2 from alveoli to blood + C02 from blood to alveoli

Question 24

how is external respiration aided by

Answer 24

a. thin respiratory membrane
b. large surface area - capillaries, alveoli
c. blood velocity slow compared to gas diffusion (rbc can pick up and release gas)

Question 25

internal respiration

Answer 25

O2 from blood to cells + CO2 from cells to blood

Question 26

partial pressure of gases

Answer 26

the pressure exerted by a single gas in a mixture of gases - e.g. O2 = 21% or air - partial P = 0.21 x 760 mm Hg = 160 mmHg

Question 27

what promotes gas movements

Answer 27

pressure gradients | e.g. air to blood , blood to cells

Question 28

how is O2 carried

Answer 28

1. dissolved in plasma (1.5%) | 2. bound to hemoglobin (98.5%)

Question 29

bound to hemoglobin

Answer 29

each hemoglobin can bind 4 O2 molecules

Question 30

dissolved in plasma

Answer 30

a, at lung capillaries - O2 moves from high pressure to low pressure b. at tissue capillaries - arterial Po2 = 95mmHg - resting venous + ISF Po2 = 40mmHg

Question 31

what is the significance of the O2-Hb dissociation curve

Answer 31

a. plateau ( between 60-100 mmHg) - if aveolar decreases little change in Hb saturation b. steep portion - at rest: ISF Po2 in tissues - O2 unloaded from Hb

Question 32

what are the shifts in O2 -Hb dissociation curve

Answer 32

a. shift to the right - for a given Po2 get less Hb saturation i.e. unloads more easily/ loads less easily b. shift to the left - for a given P02 get more Hb saturation i.e. O2 loads more easily/unloads less easily

Question 33

when does a shift to the right occur on the O2-Hb dissociation curve

Answer 33

1. increase Pco2 2. decrease pH 3. increase temp 4. all occur when increase of cell metabolism e.g. exercise

Question 34

when does a shift to the left occur in the O2-Hb dissociation curve

Answer 34

1. increase Pco2 2. higher pH 3. decrease in temp conditions at lung

Question 35

how is CO2 carried

Answer 35

1. dissolved in plasma =8% 2. bound to hemoglobin =20% 3. as bicarbonate ions =72%

Question 36

dissolved in plasma

Answer 36

a. at the lungs - alveolar PCO2 = 40 mmHg - resting venous PCO2 = 45mmHg - arterial PCO2 = 40 mmHg b. at tissues - arterial PCO2 = 4-mmHg - ICF PCO2 >45 mmHg - ISFPCO2 =45 mmHg - resting venous PCO2 = 45 mmHg

Question 37

bound to hemoglobin

Answer 37

carbamino Hb = 20% | - CO2 binds to deoxyHb better than to oxyHb

Question 38

as bicarbonate ions

Answer 38

72% a. inside RBC at tissues (increase CO2) b. inside RBC at lungs

Question 39

control of respiration

Answer 39

1. respiratory centres in medulla - set rate, depth of breathing - 2 groups of neurons - ventral (VRG) and dorsal (DRG) respiratory groups a. VRG = expiratory and inspiratory neurons b. DRG receives chemoreceptor input + modifies VRG output 2. pontine respiratory centres - work with medullary centres to make breathing smooth, even 3. other factors affecting breathing a. lung stretch receptors b. voluntary control c. chemical control d. other factors

Question 40

inspiratory neurons

Answer 40

impulses down spinal cord to a. phrenic nerve (innervates diaphragm) b. thoracic nerves (innervates external intercostals)

Question 41

expiratory neurons

Answer 41

fire to inhibit insp. neurons and expiration occurs passively

Question 42

quiet breathing VRG

Answer 42

- insp. neurons active ~ 2 seconds =insp. - expir. neurons inhibit inspire. neurons output ~ 3 seconds = expir. - VRG also active for forced insp. and expir. to recruit the additional muscles

Question 43

voluntary control

Answer 43

- 1 motor cortex to skeletal muscle - bpass medulla - if medulla damaged, must remember to breathe - hold breath - PCO2: medulla overrides voluntary control - breathe

Question 44

chemical control (chemoreceptor)

Answer 44

1. peripheral chemoreceptors: carotoid and aortic bodies - weakly sensitive to PCO2 - very sensitive to H+ - PO2 stimulates receptor when PO2 reaches ~50-60 mmHg- emergency situation 2. central chemoreceptors - medulla oblongata - responds indirectly to arterial PCO2 - resting arterial PCO2 = 40 mmHg - CO2 crosses blood-brain easily H+, HCO3, - in CSF - only detect H+ - CSF poorly buffered small change stimulates response

Question 45

clinical application

Answer 45

1. hyperventilation - decrease arterial PCO2 leads to cerebral vasocon 2. hypoventilation - increase arterial PCO2, increase H+ =acidosis leads to CNS confusion 3. CO poisoning - CO : incomplete burning of gas, coal, wood, cigarettes - CO binds 210x more strongly to Fe than O2