Airway Tone (autonomic regulation, bronconstriction, broncodilation...)

Question 1

Autonomic nervous system is split into three, which are…?

Answer 1

Parasympathetic (normal, rest and digest)
Sympathetic (fight or flight)
Enteric (GI tract)

*most organs are served by both parasympathetic and sympathetic

Question 2

What is the neurotransmitter for respi as a part of the parasympathetic nervous system?

Answer 2

Neurotransmitter: acetyl choline (ACh)

Question 3

What is the receptor for respi as a part of the parasympathetic nervous system?

Answer 3

Muscarinic 3

Question 4

What is the neurotransmitter for respi as a part of the sympathetic nervous system?

Answer 4

Noradrenaline (NAd) acts on adrenal glands to release adrenaline

Question 5

What is the receptor for respi as a part of the sympathetic nervous system?

Answer 5

Beta-2 adrenoreceptor

Question 6

What is the overall effect of Parasympathetic nervous system on respi when ACh binds with M3 in lungs?

Answer 6

bronchoconstriction

Question 7

What is the overall effect of sympathetic nervous system on respi when NAd or Ad binds to Beta-2-adrenoreceptor in lungs?

Answer 7

bronchodilation

Question 8

Describe the process of bronchoconstriction caused by Acetyl choline

Answer 8

1. Acetyl choline binds to muscarinic 3 receptor
2. Receptor couples with Gq protein
3. Gq protein activates phospholipase C (PLC)
4. Phospholipase C (PLC) catalyses breakdown of plasma membrane of phospholipid to diacylglycerol (DAG) and inositol triphosphate (IP3)
5. DAG acts as second messenger and activates a fam of proteins aka protein kinase C (PKC)
6. IP3 binds to ligand-gated Ca2+ receptors located on endoplasmic reticulum in bronchial cells, which open when IP3 is bound to them, resulting in Ca2+ release which stimulates BRONCHOCONSTRICTION

Question 9

Describe the process of bronchodilation caused by adrenaline/ noradrenaline

Answer 9

1. adrenaline/ noradrenaline binds to beta-2-adrenoreceptor
2. receptor couples with Gs protein
3. Gs protein activates Adenyl Cyclase (AC)
4. Adenyl Cyclase catalyses conversion of cyclic AMP (cAMP)
5. cAMP acts as second messenger and diffuses in lung resulting in a decrease in Ca2+ conc and activates protein kinase A (PKA) and others, eventually resulting in Bronchodilation