RESP - E. LUNG STRUCTURE AND FUNCTION-COVERED Flashcards
what is the role of the respiratory system
to ensure adequate intake of oxygen and removal of carbon dioxide
how blood flow through lungs
- deoxygenated blood from heart picks up oxygen in alveoli and excretes carbon dioxide from blood into alveoli
- pulmonary vein takes oxygenated blood to heart to be pumped around body
sympathetic nervous system
- fight or flight responses
- Noradrenaline acts at adrenoceptors in lungs
- Adrenaline released from adrenal glands
parasympathetic nervous system
- rest and digest responses
- acetylcholine acts at muscarinic receptors
adrenoceptors - alpha
- alpha1 ARs: vascular smooth muscles contraction
- alpha2 ARs: vascular smooth muscle contraction and pre-synaptic regulation of NA release
adrenoceptors - beta
- beta1 ARs - contraction of heart
- beta2 ARs - airway smooth muscle relaxation
- beta3 ARs - skeletal muscle, adipose tissue
muscarinic receptors
- M1: CNS, salivary glands, gastric glands
- M2: heart - contraction, GI smooth muscle contraction, CNS
- M3: salivary glands, smooth muscle of GIT and airways
- M4: CNS
- M5: CNS
sympathetic pathway in airways
- circulates adrenaline from adrenal glands
- acts on B2-ARs on bronchial smooth muscle = relaxation
- inhibition of mediator release from mast cells
- B2-ARs on mucous glands to inhibit secretion so increased clearance of mucous
parasympathetic pathway in airways
- release ACh
- activates muscarinic M3 receptors
- bronchoconstriction and increased mucous secretion
sensory nerves in airways
- protective mechanism
- in control of cough reflex
- cause coughing, bronchoconstriction and increased mucous secretion
- unregulated in inflammation (increased)
- involved in exercise-induced asthma?
- involved in cold-induced asthma?
*no drugs to control sensory nerves
we want to dampen the effect down
what is eupnoea
- normal breathing rhythm
- 1/3 air remains in main airways
- deeper breaths: more air passes into alveoli for gas exchange
what is dyspnoea
- difficult breathing
what is airway resistance
the opposition to airflow in respiratory tree (lungs)
- depends on friction and airway cross section
- contraction of airway smooth muscle leading to constriction of airways
- increased growth of smooth muscle (remodelling) reducing size of lumen (asthma, COPD) which increases resistance to airflow
- excess mucous production which increases resistance to airflow (chronic bronchitis common in COPD)
what is compliance
- indication of ability of lungs to stretch when breathing in
what is elastance
- ability of lung to recoil to normal size when breathing out
Emphysema/COPD can lead to loss of elastance
what is fibrosis
- caused by lung damage eg - after TB
stiff lungs (with fibrosis) have low compliance and high elastic recoil (as difficult to stretch) - total lung capacity reduces
control of breathing
- controlled though ANS
- build up of carbon dioxide (holding breath) is recognised by chemoreceptors in respiratory centres in brain stem and breathing is stimulated
what is spirometry
- measure lung volume
obstructive airway disease
- FEV1 decreases as air comes out slower
- FVC roughly the same if all air can be expelled
compared to normal
but FEV1:FVC ratio decreases
*hard for them to exhale all the air from their lungs
restrictive airway disease
- FVC decreases
- FEV1 decreases
but FEV1:FVC ratio is the same as normal
*fibrosis
*can’t fully fill their lungs with air
peak flow meter
- small, hand-held device
- measures flow of air out of lungs
- PEF - peak expiratory flow: speed at which you breathe air out
rises rapidly during forced expiration then drops - constriction of airways reduce peak flow
- record in morning and evening
respiratory acidosis
- reduction in lung function = impaired expiration of carbon dioxide
- build up of carbon dioxide leads to increased H+ conc and hence a drop in pH (acidosis)
- leads to increased breathing to limit hypoxia
- excrete more carbon dioxide, decrease carbonic acid in body and pH should rise
diabetes - build up of acids in body
hyperventilation
- leads to loss of carbon dioxide and hence alkalosis (increase in pH)
- leads to inhibition of ventilation to limit hyperventilation
vomiting out acid from stomach - decrease in ventilation to decrease carbon dioxide input and decrease pH
smoking
- causes 1/3 of all cancer deaths
- particulate matter and tar
tar is the solid material inhaled and forms a sticky brown residue in lungs and airways
