Pharmacology - Lung Structure & Function, Smoking Flashcards
Role of respiratory system
Ensure adequate intaake of O2 and removal of CO2
Structure
Trachea Bronchi Bronchial Cartidge Bronchioles Alveoli
Cystic fibrosis
Struggle with releasing fluids into lumen
Thick mucus that’s hard to move
Trap bacteria and viruses
Cause infections
Physiotherapy to remove mucus
Effect of SNS
opening up of airways
increase in heart rate
Adrenaline and NA at adrenoceptors
Effect of PNS
Constriction of airways
Increase GI motility
ACh at muscarinic receptors
α-adrenoceptor subtypes
α1: smooth muscle contraction
α2: smooth muscle contraction, pre-junctional regulation of NA release (negative feedback mechanism to control itself)
β-adrenoceptor types
β1: heart force and rate
β2: airway muscle relaxation
β3: skeletal muscle, adipose tissue
Muscarinic Receptor Types
M1: CNS, slivary glands, gastric glands
M2: Heart rate of contraction, GI smooth muscle contraction, CNS
M3: salivary glands, GI and airways smooth muscle
M4 & M5: CNS
Pathways of innervation in airways
Sympathetic:
- Adrenaline at β2-adrenoceptors –> muscle relaxation –> more O2
- Inhibition of inflammatory mediators release from mast cells –> beneficial for treating lung inflammation etc.
- Inhibition of mucus
Parasympathetic:
- ACh at M3 receptors
- Bronchoconstriction
- Increase mucus secretion
Sensory nerves:
- Local reflexes respond to irritants
- Coughing
- Bronchoconstriction
- Increase mucus secretion
Sensory nerves in exercise-induced asthma:
- cooling and dehydration –> activation of sensory nerves immune response –> bronchoconstriction –> coughs
Sensory nerves up-regulation
by inflammatory cytokines (ex: capsicum in chillis)
Sensory nerves in cold-induced asthma
TRPM8 receptors detect changes in temperature –> activation of mast cellls –> secretion of mucus
bronchoconstriction
Breathlessness causes
Cystic fibrosis Inflammation; asthma & anaphylaxis Psychological; panic attacks Pregnancy, obesity, altitude Cancer Pulmonary embolism Side effect of drugs (β-blockers, NSAIDs etc.)
Normal breathing
12 breaths/min
0.5 L/breath
eupnoea (normal rythm of breathing):
2 secs inhalation
3 secs exhalation
1/3 of air remain in main airways
Deeper breaths: more air pass into alveoli for gas exchange
Airway resistance
depend on friction & airway cross section
- contraction of airway smooth muscle
- remodelling: increased growth of smooth muscle
- reduced size of lumen (asthma, COPD etc.)
- excess mucous production (chronic bronchitis etc.)
Compliance
ability of lung to stretch
Elastance
ability of lung to recoil
Fibrosis
struggle to stretch the lung, but high recoil –> reduced capacity
Emphysema/COPD
loss of elastance
Control of Breathing
ANS
can be overridden by CNS
Spirometry
measure lung volume
VC = FVC = forced vital capacity
VT = tidal volume
TLC = total lung capacity
IRV = inspiration reserve volume
Spirometry normal result
FEV (4.0 L)
FEV1:FVC = 0.8
Spirometry obstructive disease (COPD, asthma etc.)
FEV1 (1.3 L) (struggling to force air out)
FEV1:FVC = 0.3
FEV1 = 32% of normal –> severe
FVC normal or slightly decreased
Spirometry restrictive disease (fibrosis etc.)
FEV1 = normal or slightly decreased
FEV1:FVC = normal
FVC decreased (cannot fill up lungs with air)
Peak flow meter
PEF - rise rapidly during forced expiration then drops
Constriction –> reduced peak flow –> lower number of peak flow meter
Respiratory acidosis
impaired expiration fo CO2 –> build up of CO2 –> CO2 react with water to release H+ ions –> drop in pH
long-term/chronic –> buffering with Hb in RBCs –> increase in HCO3- (bicarbonate)
acidosis vs. alkalosis? –> measure blood pH
acute vs. chronic –> HCO3- levels in plasma
breathing rate:
- acidosis –> increase in breathing to limit hypoxia
- hyperventilation –> loss of CO2 –> alkalosis –> drop in CO2 and inhibition of ventilation
- metabolic acidosis (ex: diabetes) –> drop in pH –> stimulation of ventilation
- metabolic alkalosis (ex: vomiting) –> loss of H+ –> depression of ventilation
Smoking
- one-third of all cancer deaths
- half of long-term smokers die prematurely due to smoking
Cigarette smoke contents
- Tar - solid material, form sticky brown residue
- Carcinogenics (ex: benzopyrenes –> DNA damage)
- Oxidatives
- Heavy metals (ex: cadmium)
Decline of lung function because of smoking
keeps declining even if stopped smoking before seeing any symptoms
