Pharm Tutorial 4 - Resp Flashcards
1
Q
Describe the innervation of the lungs
A
- Sympathetic innervation via nitrous oxide neurones
- Parasympathetic via acetylcholine neurones
- Acetylcholine acts at all ganglia, binding to nicotinic receptors (M1 also present), and muscarinic receptors on the smooth muscle (M3) with regulatory M2 receptors on presynaptic neuron
- Generally there is partial vasoconstriction, which allows reaction to inhalation of a small item much faster
2
Q
What is poiseuilles law?
A
- Resistance is inversely proportional to the fourth power of radius
- Therefore, small changes in airway diameter cause huge changes in radius
3
Q
Define airway resistance, compare normal and disease states
A
- Amount of pressure required to deliver a given flow of gas, expressed in terms of change in pressure divided by flow (cmH20/l/sec)
- Normal adult 0.5-1.5cmH20/l/sec
- In disease, 100cmH20/l/sec
4
Q
When is resistance increased in the airways?
A
- Mucus plugs and bronchoconstriction in asthma
- Lung fibrosis in COPD
- Turbulent air flow (minor effect) and density of inspired air (minor effect)
- Late stages of pregnancy
5
Q
How can muscarinic receptor antagonists treat COPD in smokers?
A
Prevent vasoconstriction stimulated by nicotine, by blocking M3 receptors at the smooth muscle
6
Q
What side effects are seen when taking muscarinic antagonist?
A
- Dry as a bone (reduced secretions)
- Hot as hell (reduced sweat)
- Mad as a hatter (affects neurotransmission in the brain)
- Blind as a bat (loss of accomodation)
- Tachycardia
7
Q
How can side effects of muscarinic antagonists be reduced?
A
Local administration - inhalation in COPD patients
8
Q
Why do antihistamines not help asthmatics?
A
- Histamine is one of many bronchoconstrictors (prostanoids, leukotrienes, bradykinin)
- Histamine is not very potent, acetylcholine is significantly more potent
9
Q
What can be done with asthmatics who want to do sport?
A
Take an inhaler before exercise, to prevent exercise induced asthma
10
Q
Why should asthmatics be wary of NSAIDs?
A
- NSAIDs inhibit prostaglandin production
- Some asthmatics have compensatory activation of leukotriene production by 5LO when prostaglandin production is inhibited
- Leukotrienes are bronchoconstrictors and increase mucus production
11
Q
How can leukotriene inhibitors be useful in asthmatics?
A
- In asthmatics sensitive to aspirin, leukotrienes contribute towards bronchoconstriction and mucus production
- Blocking this could therefore improve asthma
