Physiology Flashcards
what is internal respiration
intracellular mechanisms where O2 is consumed and CO2 is produced
what is external respiration
sequence of events that lead to the exchange of CO2 and O2 between external environment and cells
what are the 4 steps of external respiration
ventilation
gas exchange (alevoli and blood)
Gas transport
gas exchange (at tissue)
what 4 systems are involved in respiration
resp, cardio, haemotology, nervous
define ventilation
The mechanical process by which air is moved between the atmosphere and the alveolar air sacs
what is boyle’s law
at constant temp, pressure exerted by gas varies inversely with volume of gas. As the volume the gas is contained in increases, the pressure decreases
what forces hold the lung and thoracic walls in close opposition
intrapleural fluid cohesiveness and negative intrapleural pressure
describe intrapleural fluid cohesiveness
water molecules in intrapleural fluid are attracted to each other and resist being pulled apart, sticking membrane together
describe negative intrapleural pressure
intrapleural pressure is less than lungs which creates a transmural pressure gradient, allowing them to expand outwards
in order for air to move into the lungs, what must the intra-alveolar pressure be and why
lower than atmospheric, follows pressure gradient from high –> low (boyles law)
directly before inspiration, what is the intra-alveolar pressure
= to atmospheric
is inspiration active or passive
active, depends on muscle contraction
what does contraction of the diaphragm do
increases thoracic volume vertically (decreases pressure in lungs)
what does contraction of external intercostal muscle do
lifts ribs and moves back sternum
is expiration active or passive
passive
what happens when lungs recoil to normal size
increases the pressure in the lungs (air leaves as pressure less in atmosphere)
why do lungs recoil in expiration
alveolar surface tension and elastic connective tissue
what is alveolar surface tension
attraction between water molecules with air in-between
what does alveolar surface provide
strength and prevention of collapse
what are alveoli with smaller radii more likely to do
collapse
what do type II alveoli secrete and why
surfactant (lipids and proteins), to lower surface tension and prevent collapse
what is alveolar interdependence
surrounding alveoli recoil to pull it open
what is a pneumothorax
air in pleural space
what do pneumothorax result in and why
collapsed lung as abolishes pressure gradient
what is respiratory distress syndrome of newborns
lungs can’t synthesis surfactant
what are the major muscles of inspiration
diaphragm and external intercostal muscles
what are the accessory muscles of inspiration
sternocleidomastoid, scalenus, pectoral
what are the active muscles of expiration
abdominal muscles and internal intercostal muscles
what is the tidal volume (TV)
volume of air entering/ leaving the lungs in a single breath
what is the inspiratory reserve volume (IRV)
extra volume that can be inspired beyond TV
what is the inspiratory capacity (IC)
maximum volume of air that can be inspired TV + IRV
what is the expiratory reserve volume (ERV)
extra volume that can be expired after tidal volume
what is the residual volume (RV)
the volume left in lungs after maximal expiration (can’t be measured with spirometry)
what is the functional residual capacity (FRC)
volume of air in lungs after normal expiration (RV + ERV)
what is the vital capacity (VC)
maximum volume of air that can be expired after maximum inspiration (IRV + TV + ERV)
what is the total lung capacity (TLC)
RV + VC
what is the forced vital capacity (FVC)
maximum volume that can be forcibly expired following maximum inspiration
what is the forced expiratory volume in a second (FEV1)
forced expired volume in 1 second of FVC
what is the normal FEV1/FVC ratio
70%
in an obstructive lung disease (eg asthma) what would the FEV1, FVC and FEV1/ FVC show
FVC = normal/ low
FEV1 = low
FEV1/ FVC = low
in a restrictive lung disease what would the FEV1, FVC and FEV1/FVC show
FVC low
FEV1 low
FEV1/FVC normal
in a combination of restrictive and obstructive what would FEV1 etc show
errything low
what is the biggest factor in airway resistance
radius
what does parasympathetic stimulation have on the lungs
bronchocontriction
what does sympathetic stimulation have on the lungs
bronchodilation
what is the dynamic airway compression
as we expire, the rising intrapleural pressure squeezes the alveoli and forces the air out of them (like toothpaste)
what can peak flow be used to diagnose
obstructive lung disease eg asthma and COPD
what is pulmonary compliance
how easy/ difficult it is to stretch the lungs
what does decreased compliance mean and what can cause it
more effort to inflate, restrictive pattern (pulmonary fibrosis, oedema, collapse, pneumonia)
what does increased compliance mean and what can cause it
elastic recoil is lost, lungs stay inflated (hyperinflated) and it is harder to breath out. obstructive pattern (COPD)
how is working of breathing increases
increased resistance, decreased compliance, decreased recoil and need for ventilation
what is pulmonary ventilation
volume of air breathed in and out per minute (resp rate x TV)
what is dead space, what affect does it have on alveolar ventilation
volume of air that is inspired but not exchanged, decreases it
what is alveolar dead space
ventilated alveoli with inadequate blood perfusion
what is the physiological dead space
anatomical dead space + alveolar dead space
how can pulmonary ventilation be increased
increasing depth and resp rate
where is the most blood flow in the lungs
bottom
what effect does accumulation of CO2 due to increased perfusion have on the airflow and resistance
increases perfusion and airflow, decreases resistance
what effect does increased O2 due to increased ventilation
vasodilation
what are the 4 factors affecting gas exchange
partial pressure gradient of O2 and CO2.
Diffusion coefficient for O2 and CO2.
surface area of alveolar membrane.
Thickness of alveolar membrane
what is the partial pressure of a gas
the pressure a gas exerts in a mixture of gases
which has a larger partial pressure
oxygen
what is the diffusion coefficient of a gas
solubility of a gas across membranes
how much greater is the diffusion coefficient of CO2 than O2
20 (20x more soluble)
what is ficks law of diffusion
amount of gas that moves across a tissue is proportional to the area and thickness of tissue
what is henry’s law
amount of gas dissolved in a volume of liquid is proportional to the partial pressure
if the partial pressure increased, what would happen to the concentration of a gas
increase
what are the 2 ways O2 is transported in the blood and which is more prominent
dissolving (1.5%) and haemoglobin (98.5%)
how may heam groups does HB have, how much O2 binds to each
4, 1 O2 molecule
what increases % saturation of HB
partial pressure of O2
what is the O2 content of arterial blood determined by
HB concentration and saturation
what can impair O2 delivery
resp diseases, anaemia and heart failure
what happens to the pressure as blood moves from pulmonary capillaries to systemic capillaries
decreases
what happens to HB’s affinity for O2 when 1 molecule binds
increases affinity, cooperativity effect
what is the Bohr effect
shift to the right in O2 curve, more O2 released at lower partial pressure of O2 (tissues)
what factors influence the bohr effect
increases pressure of CO2, increased acidity and increased temp
how does foetal Hb differ from adult Hb
has 2 alpha and 2 gamma subunits, increasing it’s affinity for O2 and can transfer even at low oxygen pressure
where is myoglobin mainly found
skeletal and cardiac muscle
why is myoglobin needed
releases O2 at very low Po2, short term storage for O2 in anaerobic conditions
what is the ratio of O2 to myoglobin
1:1
what does myoglobin indicate
muscle damage
how is CO2 carried
10% solution, 60% bicarbonate, 30% carbamino compounds
where does the formation of bicarbonate (HCO3) happen and what catalyses it
red blood cells, carbonic anhydrase
how do carbamino compounds form
amino group + CO2 in blood proteins
where does CO2 bind to in heamoglobin and what does this form
globin, carbamino-haemoglobin
what is the haldane effect
removing O2 from Hb increases it;s ability to pick up CO2 and CO2 generated H+
what 2 effects work together to facilate O2 release and Co2 pickup
Bohr and haldane
