Respiratory Physiology

Question 1

what 2 things does airways resistance depend on ?

Answer 1

• airway diameter
• whether the flow is laminar of turbulent

Question 2

what 2 factors does poiseuille’s law link ?

Answer 2

gives relationship between airway resistance and diameter of airway

Question 3

what impact does sympathetic innervation have on airway diameter ? via what receptors ? give an example of when this might happen ?

Answer 3

SNS innervation => bronchial smooth muscle relaxation (via beta-2-receptors) => increase airway diameter
(like when exercising)

Question 4

what impact does parasympathetic innervation have on airway diameter ? via what receptors ?

Answer 4

PSNS innervation => increase smooth muscle contraction (via muscarinic (M3) receptors => reduce airway diameter

Question 5

What is radial traction ?

Answer 5

elastic fibres surround alveoli pull on walls of small airways => stay open (prevents airway collapse)

Question 6

what is surfactant and what produces it ?

Answer 6

type II alveolar cells secrete surfactant => overcome surface tension => allow alveoli to expand => prevent atelectasis

Question 7

lung volumes: what is expiratory reserve volume ?

Answer 7

extra vol that can expired below tidal vol

Question 8

how are TLC + RV affect in obstructive lung diseases ? restrictive lung diseases ?

Answer 8

• obstructive: Increases TLC + RV (due to air trapping)
• restrictive: decreases TLC + RV

Question 9

lung volumes: what is residual capacity ?

Answer 9

vol remaining after maximum expiration

Question 10

lung volumes: what is functional residual capacity ?

Answer 10

volume remaining after quiet expiration

Question 11

lung volumes: what is inspiratory capacity ?

Answer 11

volume breathed in from quiet expiration to max inspiration

Question 12

what is anatomical dead space ? where ?

Answer 12

volume of air that never reaches alveoli so never participates in respiration (trachea => terminal bronchioles)

Question 13

what is alveolar dead space ?

Answer 13

vol of air that reaches alveoli but not involved in resp due to lack of ventilation of perfusion (Like PE)

Question 14

what lung volumes can spirometry measure ?
what can it not measure ?

Answer 14

can measure tidal vol, insp reserve vol, exp reserve col
- no reserve vol

Question 15

what tests can be used to measure anatomical dead space >

Answer 15

nitrogen wash out

Question 16

what test can be done to measure total lung capacity ?

Answer 16

helium dilution study measure total lung capacity

Question 17

spooning on flow col loop would indicate what ?

Answer 17

an obstructive disease

Question 18

describe FEV1, FVC and FEV1/FVC in obstructive disease ?

Answer 18

• FEV1: < 0.8
• FVC: reduced bit not same degree as FEV1
• FVC/FEV1: < 0.7

Question 19

describe FEV1, FVC and FEV1/FVC in restrictive disease ?

Answer 19

• FEV1: < 0.8
• FVC: < 0.8
• FEV1/FVC : > 0.7

Question 20

is inspiration an active or passive process ? describe

Answer 20

active contraction of muscles
- diaphragm flattens
- external intercostal muscles (elevate the ribs + sternum)

Question 21

is expiration an active or passive process ? describe

Answer 21

normal expiration is passive
- relaxation of inspiratory muscles

Question 22

describe active inspiration ? what involved

Answer 22

additional contraction of accessory muscles
(scalenes, sternocleidomastoid, pec major + minor, serrates anterior, lattismus dorsi)

Question 23

describe active expiration ? what involved ?

Answer 23

contraction of anterolateral abdo wall, internal intercostal, innermost intercostal

Question 24

what factors affect rate of diffusion of gas ?

Answer 24

• concentration gradient
• SA for diffusion
• length of diffusion pathway

Question 25

describe density and solubility of o2 compared to co2

Answer 25

oxygen is a less dense collude that co2 and less soluble (so co2 diffuses faster into liquid)

Question 26

what 2 ways is oxygen transported in blood ? which more common ?

Answer 26

- bound to haemoglobin (99%) - dissolved in blood (1%)

Question 27

how many oxygen moves can haemoglobin bind to ?

Answer 27

each haemoglobin molecule has 4 subunits so can bind 4 oxygen molecules (=> oxyhemoglobin)

Question 28

what is the Bohr effect ?

Answer 28

when H+/pCO2 increases (and pH goes down) => haemoglobin decreases its affinity for O2 => optimise O2 delivery (for aerobic respiration)

Question 29

What is cooperatively in terms of haemoglobin and oxygen ?

Answer 29

as more oxy bind to have, it becomes easier for further oxy to bind

Question 30

what is the Mx of carbon monoxide poisoning ?

Answer 30

100% oxygen + referral to hyperbaric oxygen treatment

Question 31

what is the main role of CO2 in the body ?

Answer 31

to regulate pH of blood (more important than transport CO2 to lungs for exhalation)

Question 32

in what 3 ways is CO2 transported in the blood ?

Answer 32

- carb amino compounds (carried in RBC - CO2 directly bind to AA, helps prevent entering blood and lowering pH) - hydrogen carbonate (dissolved in RBC: HCO3- dissolved in plasma as carbonic acid) - CO2 dissolved in plama (10%)

Question 33

describe ventilation vs perfusion when upright ? at apex vs at base ?

Answer 33

when upright: - ventilation exceeds perfusion towards apex (V/Q>1) - perfusion exceeds ventilation towards base (V/Q<1)

Question 34

where are peripheral chemoreceptors located ? what do they detect changes in ?

Answer 34

located carotid sinus and aortic arch - detect large changes in pO2

Question 35

peripheral chemoreceptor detects reduced O2 - what happens ?

Answer 35

low O2 detected => afferent impulse along CN IX + X => increased RR + TV, increased blood flow to brain + kidney (as these are most sensitive to hypoxia)

Question 36

where are central chemoreceptors located ? what do they detect changes in ?

Answer 36

located in medulla oblngata - detect changes in arterial pCO2

Question 37

how does ACEi cause dry cough ?

Answer 37

ACEi even activation of bradykinin =? accumulate in resp tract => irritation of C-fibres => hyper stimulation of cough reflex

Question 38

name the two classes of bronchodilators ? how they work

Answer 38

- beta agonist: adrenergic (SNS) => bronchodilation - Ache antagonist: anti-cholinergic (PSNS) => blocks bronchoconstriction