ANS and Respiratory System Flashcards
What can be seen in a cross-section through airways?
(Inside out)
- Lumen
- Mucosal layer
- Submucosa
- Smooth muscle
What is the affect of cigarette smoke on the lumens of airways?
- Allergens, irritants, chemicals may enter lumen
- Contraction of airways smooth muscle leads to narrowing and bronchoconstriction
What is asthma characterised by?
- Intermittent brinchicinstriction caused by allergens or non-specific stimuli such as cold air
What is the risk of long-term exposure to irritants such as smoke, air pollution and isocyanates?
Chronic obstructive pulmonary disease
How is bronchial smooth muscle controlled?
- Parasympathetic innervation
- Relaxed by actions of circulating adrenaline on β adrenoceptors
What types of drugs mimic the effects of adrenaline?
- β-agonists
- Relax smooth muscle regardless of contractile stimulus
- Also muscarinic antagonists
What does noradrenaline stimulate?
- Potent stimulus for α receptors
- Less effective against β-adrenoceptors
What does adrenaline stimulate?
- Potent stimulus for both α and β adrenoceptors
What are the actions of adrenaline on the alpha-1 receptors?
- Constriction of blood vessels in skin and gut
- Dilation of pupil
What are the actions of adrenaline on the alpha-2 receptors?
- Increased renin secretion in the kidney
- Glycogenolysis in the liver
- Decreased GI motility
What are the actions of adrenaline on the β-1 adrenoceptors?
- Increased heart rate and force of contraction
What are the actions of adrenaline on the β-2 adrenoceptors?
- Dilation of blood vessels in skeletal muscle
- Increased renin secretion in the kidney
- Glycogenolysis in the liver
- Decreased GI motility
- Relaxation of bronchial smooth muscle
What are the uses of adrenaline?
- Used to treat severe asthma for rapid reversal of bronchoconstriction is required
- Also used in anaphylaxis where there is an explosive release of hits,ine
- Adrenaline is metabolised relatively quickly
- -> Wears off quickly in around 30 minutes-1hour
What autonomic innervation does the heart have?
- Both sympathetic and parasympathetic innervation
What does stimulation of β-1 adrenoceptors in the heart lead to?
- Increased force of contraction, increased heart rate and reduced cardiac efficiency
- Oxygen consumption is increased more than cardiac work
- Also helps restore automaticity of heart
What are the characteristics of an ideal drug for asthma?
- Selective- no toxic side effects
- Rapid onset of action
- Appropriate route of administration
- Appropriate duration of action
- Cheap and easy to produce
Describe the development of selective β agonists
1) noradrenaline α>β
2) adrenaline α=β
3) isoprenaline β>α
4) salbutamol β-2>β-1»α
- There is increasing sensitivity to β adrenoceptors
What are the effects of β-2 adrenoceptor agonists?
- Relax airway smooth muscle
- Inhibit mediator release from mast cells
- Inhibit release of TNF-α from macrophages
- Increase mucus clearance via action on cilia
- Muco-ciliary escalator
What are the uses of β-adrenoceptor agonists?
- Salbutamol is used to relieve symptoms of asthma
- Rapid action
- Relaxes smooth muscle regardless of stimulus
- Βeta-2 adrenoreceptor agonists do not affect underlying airways inflammation and over-reliance on this form of therapy should be avoided
How are β-2 agonists administrated?
- Inhaled to reduce side effects
- Can be given as an aerosol, powder or nebulised solution
- Occasionally orally or via injection
What is a nebulised solution?
Fine mist that can reach smaller airways (larger dose)
What are the effects of excessive salbutamol?
- Skeletal muscle tremor
- Hyperglycaemia in diabetic patients
- Cardiovascular effects- arrhythmias acutely and potentially myocardial ischaemia in long-term
- Hypokalaemia-
- Overuse may down-regulate β-adrenoceptor expression
- No improvement in underlying airways inflammation
Give an example of a longer-acting β-2 agonist
- Salmeterol
- Duration of action-12 hours
- Patients that may constantly need Bronchodilation
- Used twice daily to control symptoms
- May be combined with steroid to reduce airway inflammation
What is the issue with longer acting β-2 agonists?
- High death rate linked to over-reliance on high dose, long-acting β-agonist
- Once drug removed from market, death rate fell
