respiratory teach - physiology Flashcards
what happens in sneezing?
certain stimulants trigger histamine release in nasal cavity
activate trigeminal nerve to send impulse to brainstem
causes expiratory muscles and vocal muscle to contract = sneezing
obstructive disease
increasing resistance e.g. asthma FVC same FEV1 decreases ratio decreases
restrictive disease
decreasing compliance e.g. pulmonary fibrosis FVC decreases FEV1 decreases ratio same
resistance
ease at which gas flows
compliance
expandability of lungs and chest wall
spirometry trace for COPD
higher than normal
gentler downwards slope
mixed obstructive and restrictive disease
inspiration limited by restrictive disease
expiration limited by obstructive disease
wheeze
expiration
from bronchioles
stridor
inspiration
from larynx
what happens in inspiration
inspiratory muscles contract
increase volume of thorax
intrapleural pressure more negative which increases difference between alveolar and intrapleural pressure
increases transpulmonary pressure
so alveolar volume increase
alveolar pressure decreases
creates a pressure gradient so breathe in
what happens in expiration
inspiratory muscles relax intrapleural pressure becomes less negative decreases difference between alveolar and intrapleural pressure decreases transpulmonary pressure alveoli get smaller volume decreases alveolar pressure increase makes pressure gradient so breathe out
what is transpulmonary pressure
ptp
alveolar pressure - intrapleural pressure
synonymous with alveolar expansion
what is Palv?
pressure in alveoli
what is Pip?
intrapleural pressure
what is Patm?
atmospheric pressure
what muscles are involved in inspiration?
diaphragm external intercostals sternocleidomastoid scalenes pec major pec minor serratus anterior
what muscles are involved in expiration?
internal intercostals innermost intercostals rectus abdominis transversus abdominis external and internal oblique
innervation of diaphragm?
phrenic nerve
spinal root of phrenic nerve?
C3,4,5
V/Q matching
ventilation/ perfusion matching
how are ventilation and perfusion matched?
greater ventilation and greater perfusion at bottom of lungs, so they are well matched
benefit of V/Q matching?
maximise the exchange of oxygen across alveoli
pulmonary shunt
where ventilation is cut off in the lung so blood gets no oxygen so V/Q is 0
dead space
where blood supply to alveoli are cut off so V/Q is higher
bohr effect
higher CO2 - near respiring cells
decreases haemoglobin affinity for oxygen
oxygen dissociates from haemoglobin
more oxygen released
haldane effect
higher O2 - near lungs
increases haemoglobin affinity for oxygen
oxygen combines with haemoglobin and displaces CO2
more oxygen taken up by haemoglobin
fetal haemoglobin
greater affinity for O2
polycythaemia
what is polycythaemia?
higher concentration of haemoglobin
greater number of RBCs due to more RBCs or less plasma
