Respiratory Physiology Flashcards
what 2 things does airways resistance depend on ?
- airway diameter
- whether the flow is laminar of turbulent
what 2 factors does poiseuille’s law link ?
gives relationship between airway resistance and diameter of airway
what impact does sympathetic innervation have on airway diameter ? via what receptors ? give an example of when this might happen ?
SNS innervation => bronchial smooth muscle relaxation (via beta-2-receptors) => increase airway diameter
(like when exercising)
what impact does parasympathetic innervation have on airway diameter ? via what receptors ?
PSNS innervation => increase smooth muscle contraction (via muscarinic (M3) receptors => reduce airway diameter
What is radial traction ?
elastic fibres surround alveoli pull on walls of small airways => stay open (prevents airway collapse)
what is surfactant and what produces it ?
type II alveolar cells secrete surfactant => overcome surface tension => allow alveoli to expand => prevent atelectasis
lung volumes: what is expiratory reserve volume ?
extra vol that can expired below tidal vol
how are TLC + RV affect in obstructive lung diseases ? restrictive lung diseases ?
- obstructive: Increases TLC + RV (due to air trapping)
- restrictive: decreases TLC + RV
lung volumes: what is residual capacity ?
vol remaining after maximum expiration
lung volumes: what is functional residual capacity ?
volume remaining after quiet expiration
lung volumes: what is inspiratory capacity ?
volume breathed in from quiet expiration to max inspiration
what is anatomical dead space ? where ?
volume of air that never reaches alveoli so never participates in respiration (trachea => terminal bronchioles)
what is alveolar dead space ?
vol of air that reaches alveoli but not involved in resp due to lack of ventilation of perfusion (Like PE)
what lung volumes can spirometry measure ?
what can it not measure ?
can measure tidal vol, insp reserve vol, exp reserve col
- no reserve vol
what tests can be used to measure anatomical dead space >
nitrogen wash out
what test can be done to measure total lung capacity ?
helium dilution study measure total lung capacity
spooning on flow col loop would indicate what ?
an obstructive disease
describe FEV1, FVC and FEV1/FVC in obstructive disease ?
- FEV1: < 0.8
- FVC: reduced bit not same degree as FEV1
- FVC/FEV1: < 0.7
describe FEV1, FVC and FEV1/FVC in restrictive disease ?
- FEV1: < 0.8
- FVC: < 0.8
- FEV1/FVC : > 0.7
is inspiration an active or passive process ? describe
active contraction of muscles
- diaphragm flattens
- external intercostal muscles (elevate the ribs + sternum)
is expiration an active or passive process ? describe
normal expiration is passive
- relaxation of inspiratory muscles
describe active inspiration ? what involved
additional contraction of accessory muscles
(scalenes, sternocleidomastoid, pec major + minor, serrates anterior, lattismus dorsi)
describe active expiration ? what involved ?
contraction of anterolateral abdo wall, internal intercostal, innermost intercostal
what factors affect rate of diffusion of gas ?
- concentration gradient
- SA for diffusion
- length of diffusion pathway
describe density and solubility of o2 compared to co2
oxygen is a less dense collude that co2 and less soluble (so co2 diffuses faster into liquid)
what 2 ways is oxygen transported in blood ? which more common ?
- bound to haemoglobin (99%)
- dissolved in blood (1%)
how many oxygen moves can haemoglobin bind to ?
each haemoglobin molecule has 4 subunits so can bind 4 oxygen molecules (=> oxyhemoglobin)
what is the Bohr effect ?
when H+/pCO2 increases (and pH goes down) => haemoglobin decreases its affinity for O2 => optimise O2 delivery (for aerobic respiration)
What is cooperatively in terms of haemoglobin and oxygen ?
as more oxy bind to have, it becomes easier for further oxy to bind
what is the Mx of carbon monoxide poisoning ?
100% oxygen + referral to hyperbaric oxygen treatment
what is the main role of CO2 in the body ?
to regulate pH of blood (more important than transport CO2 to lungs for exhalation)
in what 3 ways is CO2 transported in the blood ?
- 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%)
describe ventilation vs perfusion when upright ? at apex vs at base ?
when upright:
- ventilation exceeds perfusion towards apex (V/Q>1)
- perfusion exceeds ventilation towards base (V/Q<1)
where are peripheral chemoreceptors located ? what do they detect changes in ?
located carotid sinus and aortic arch
- detect large changes in pO2
peripheral chemoreceptor detects reduced O2 - what happens ?
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)
where are central chemoreceptors located ? what do they detect changes in ?
located in medulla oblngata
- detect changes in arterial pCO2
how does ACEi cause dry cough ?
ACEi even activation of bradykinin =? accumulate in resp tract => irritation of C-fibres => hyper stimulation of cough reflex
name the two classes of bronchodilators ? how they work
- beta agonist: adrenergic (SNS) => bronchodilation
- Ache antagonist: anti-cholinergic (PSNS) => blocks bronchoconstriction
