respiratory physiology Flashcards
what is intrapleural pressure relative to intrapulmonary pressure (pressure within the alveoli)
-4 drops to -6 on inspiration which decreases intrapulmonary pressure by -1. this increases the volume by 500mls
describe how the pressure changes
decreases on inspiration and increases on expiration
what is the equation linking airflow to airway resistance
flow = change in pressure / resistance
what is work of breathing
energy required to
contract muscle
stretch elastic components
overcome airway resistance
overcome friction and inertia
where is the greatest resistance to airflow found
segmental bronchi
low cross sectional area and high airflow and turbulence
what is compliance
the ease of distensibility of the lung tissue when an external force is applied
the change in volume of the chest for a given change in pressure
determined by elastic components and alveolar surface tension
healthy = 1L per kPa
how can you change compliance?
decrease: pulmonary fibrosis
blocking smaller resp passages
increases surface tension
decreasing flexibility of the thoracic cage
increase: emphysema by reducing surface tension. also poor deflation leading to trapped air and barrel chest
lung compliance also changes with lung volume which explains differences between the base and apex. the base volume is less so more compliant
what produces surfactant
type 2 alveolar cells
made of phospholipids
prevents alveolar collapse and increases compliance
what are the 4 lung volumes
expiratory reserve volume
inspiratory reserve volume
tidal volume
residual volume
what are the 4 lung capacities
vital capacity
total lung capacity
inspiratory capacity
functional residual capacity
what is dead space
anatomical: parts of airways not involved in gas exchange
functional: anatomical plus alveolar where gas exchange is suboptimal
describe a vitalograph reading for a restrictive lung disease
FEV1 is reduced
FEV1 divided by FVC is normal
describe a vitalograph from an obstructive airway disease
FEV1 is reduced
where are the respiratory centres located
medulla and pons
what are the two pontine centres
pneumotaxic
apneustic
what are the two medullary centres
inspiratory- upper part of medulla aka DRG
expiratory in the anterolateral part aka VRG
pneumotaxic centre function and location
upper pons
controls medullary resp centres esp DRG
location of the apneustic centre and function
lower pons
increases the depth of inspiration by acting on the DRG
what afferent nerves are involved in respiration
vagus and glossopharyngeal
what information does the resp centre receive
chemoreceptor and info about movement of the thorax
what higher centres can influence the respiratory centres
cerebral cortex, limbic, hypothalamus
what is the Hering breur reflex
when the lung inflates neurones send impulses to the DRG which prevents over inflation
what a J receptors aka pulmonary C fibres
juxtacapillary receptos present in the walls of the alveoli
stimulated in oedema, congestion, pneumonia and histamine
induces apnea and rapid shallow breathing
what do irritant receptors do
situated on the walls of bronchi and bronchioles
stimulated by harmful chemicals
induces rapid shallow breathing and long deep breaths to reverse slow lung collapse
what do proprioceptors do
found in chest wall, joints, tendons, muscle spindles
stablises ventilation
what do thermoreceptors do
stimulates hyperventilation to the cerebral cortex
what do pain receptors do`
signal to resp centre, signals hyperventilation
what does the cough reflex do
stimulates vagus nerve
forced expiration against closed glottis due to irritants
what is the sneezing reflex
irritation of nasal mucous membranes
forceful expiration with open glottis
what is the deglutition reflex
swallowing apneoa
what do chemoreceptors detect
hypoxia
hypercapnia
ph
where are central chemoreceptors found
medulla oblongata close to DRG
sensitive to increase in H+
H+ cannot cross BBB but CO2 can which forms H+
sensitive due to low buffering in CSF
where are peripheral chemoreceptors found
carotid sinus and aortic arch
carotid bodies more important in respiration
detects O2, CO2, pH, blood flow and temp
describe some diseases affecting ventilation
CNS trauma
stroke
poliomyelitis
diptheria
botulism
Duchennes muscular distrophy
