Neurohumoral control of the airways, bronchodilator drugs and asthma Flashcards
What does the vagus nerve carry?
Preganglionic fibres
Where are ganglia embedded?
In the walls of bronchi and bronchioles
What does parasympathetic stimulation cause?
Bronchial smooth muscle contraction mediated by ACh acting upon M3 muscarinic ACh receptors
Increased mucus secretion mediated by ACh acting upon M3 muscarinic ACh receptors
Collectively increased airways resistence
In the sympathetic division what do the postganglionic fibres supple?
Sub-mucosal glands and smooth muscle of blood vessels
What does sympathetic stimulation cause?
Bronchial smooth muscle relaxation via Beta 2 adrenoceptors activated by adrenaline released from the adrenal gland
Decreased mucus secretion mediated by Beta 2 adrenoceptors
Increased mucociliary clearance mediated by beta 2 adrenoceptors
Collectively reduced airway resistance
What pathological changed does chronic asthma do to the bronchioles due to long standing inflammation?
Increase mass of smooth muscle - hyperplasia and hypertrophy
Accumulation of interstitial fluid (oedema)
Increased secretion of mucus
Epithelial damage (exposing sensory nerve endings)
What does airway narrowing increase and decrease?
Increases airway resistance and decreases FAV1 and PEFR
What does epithelial damage do?
Contributes to increases sensitivity of the airways to bronchoconstrictor influences - hypersensitivity and hyperactivity
What are the two stages of an asthma attack?
immediate - bronchospasm
Delayed - inflammation
What is the difference in responses to an allergen between an atopic and a nonatopic individual?
In an atopic the response is strong antibody mediated immune response involving IgE
In a nonatopic individual the response is low level and cell mediated immune response involving IgG and macrophages
What does the presentation of antigen do to mast cells?
Stimulated calcium entry into mast cells which causes a release of calcium from intracellular stores evoking:
release of secretory granules containing performed histamines and the production and release of other agents that cause airway smooth muscle contraction
Release of substances such as platelet activating factors and prostaglandins which attract cells causing inflammation into the area
In the immediate stage the allergen activates mast cells and which two groups of substances are released?
- spasmogens, cysLTs, histamine- —> this causes BRONCHOSPASM
- chemotaxins, chemokines-
Chemotaxins and chemokines then mediates the late phase what happens then?
EPITHELIAL DAMAGE
AIRWAY INFLAMMATION
AIRWAY HYPERREACTIVITY
BRONCHOSPASM, WHEEZING, COUGH
What are the two types of drugs used in asthma?
relievers - act as bronchodilators - SAB
controllers/preventors act as anti-inflammatory agents that reduce airway inflammation - glucocorticoids
what are the side effects of beta 2 aderenoceptor agonists
fine tremor and occasional tachycardia
